Physics Events
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JUN
28
Friday
Physics Department Summer Lecture Series
"Using Gravitational Lensing to measure Dark Matter and Dark Energy in the Universe"
Presented by Erin Sheldon, BNL
12:30 pm, Small Seminar Room, Bldg. 510
Friday, June 28, 2019, 12:30 pm
Hosted by: Mary Bishai
Gravitational lensing is the bending of the path of light near massive bodies. Mass produces a curvature of space time, and light follows a curved path that is calculable using the General Theory of Relativity. I will discuss how the lensing effect is used to measure the amount of Dark Matter in galaxies and in the universe as a whole. I will also discuss how we use lensing to measure the properties of the mysterious Dark Energy that is driving the accelerated expansion of our universe.
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JUL
1
Monday
Particle Physics Seminar
"Searches of Dark Matter signals with the ATLAS detector at the LHC: Present and future"
Presented by Dr. Rachid Mazini, Academia Sinica, Taiwan
3 pm, Small Seminar Room, Bldg. 510
Monday, July 1, 2019, 3:00 pm
Hosted by: Alessandro Tricoli
In this seminar, I will present an overview of up-to-date results on searches for Dark Matter signals with the ATLAS detector at the LHC using Run 2 data. Comparison with non-accelerator DM results as well as interpretation within some theoretical models will be discussed. In addition, expectation from the high-luminosity LHC (HL-LHC) DM searches program will be briefly presented. Finally, I will talk about the new ATLAS High Granularity Timing Detector (HGTD), planned for the phase 2 upgrade program for the HL-LHC run, and it performances for physics studies.
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JUL
2
Tuesday
Physics Department Summer Lecture Series
"Astronomical CCDs"
Presented by Andrei Nomerotski, BNL
12:30 pm, Small Seminar Room, Bldg. 510
Tuesday, July 2, 2019, 12:30 pm
Hosted by: Mary Bishai
I will review how the state-of-the-art sensors developed for astronomical applications can precisely measure the positions and shapes of billions of galaxies. The talk will also provide more detail on the camera and sensors for the Large Synoptic Survey Telescope (LSST) and will discuss limitations on the achievable precision coming from the instrumentation.
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JUL
12
Friday
Physics Department Summer Lecture Series
"A golden age in physics, an overview of what the...is going on in the RHIC tunnel"
Presented by Rob Pisarski, BNL
12:30 pm, Small Seminar Room, Bldg. 510
Friday, July 12, 2019, 12:30 pm
Hosted by: Mary Bishai
I will give a general introduction to the modern theory of "strong" interactions, which involve quarks and gluons. At about a trillion degrees, these form a Quark-Gluon Plasma, which we believe is created in the collisions of heavy ions at very high energies, such as at the Relativistic Heavy Ion Collider here at Brookhaven. I also make extensive comments about the sociology of the field, especially the phenomenon of "As everyone who is anyone knows..."
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Physics Department Summer Lecture Series
"Basics of Neutrino Interactions in Matter"
Presented by Milind Diwan, BNL
Tuesday, June 18, 2019, 12:30 pm
Small Seminar Room, Bldg. 510Hosted by: Mary Bishai
I will review the basics of neutrino interactions in matter with emphasis on calculations of cross sections and rates. The lecture will provide introduction to the physics of weak interactions.
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Nuclear Physics Seminar
"First observation of the directed flow of D0 and anti-D0 in Au+Au collisions at sqrt(sNN) = 200 GeV"
Presented by Subhash Singha, KSU
Tuesday, June 18, 2019, 11 am
Small Seminar Room, Bldg. 510Hosted by: Isaac Upsal
In this talk, we will present the first measurement of rapidity-odd directed flow (v1) for D0 and anti-D0 mesons at mid-rapidity (|y| < 0.8) in Au+Au collisions at sqrt(sNN) = 200 GeV using the STAR detector at the Relativistic Heavy Ion Collider. In 10-80% Au+Au collisions, the slope of the v1 rapidity dependence (dv1/dy), averaged over D0 and anti-D0 mesons, is -0.080 +/- 0.017 (stat.) +/- 0.016 (syst.) for transverse momentum (pT) above 1.5 GeV/c. The absolute value of D0-meson dv1/dy is about 25 times larger than that for charged kaons, with 3.4sigma significance. These data not only give unique insight into the initial tilt of the produced matter, they are expected to provide improved constraints for the geometric and transport parameters of the hot QCD medium created in relativistic heavy-ion collisions.
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Condensed-Matter Physics & Materials Science Seminar
"Tracking phase textures in complex oxides using coherent x-rays"
Presented by Xiaoqian Chen, Lawrence Berkeley Laboratory
Monday, June 17, 2019, 11 am
ISB Bldg. 734, Conf. Rm. 201 (upstairs)Hosted by: Ian Robinson/Mark Dean
In complex oxides, coupled interactions result in unpredictable and novel emerging orders that are yet to be understood. With the recent advancement in x-ray and laser sources, exploration of equilibrium fluctuation and nonlinear dynamics have become an effective approach to understand these intertwined orders. In particular, coherent x-rays are a simultaneous probe of the order parameter, phase texture, and dynamics. In the first part of my talk, I will use underdoped cuprate La2-xBaxCuO4 as an example to show how x-ray speckle correlation can be a test for (lattice degree of freedom and charge) order coupling and dynamics. However, can we image domain dynamics in real time? In the second part of my talk, I will use antiferromagnetically ordered artificial lattice to demonstrate that phase retrieval lensless imaging can be used to image charge and magnetic orders. Using Bragg coherent diffraction imaging, we revealed a single domain wall motion with 100ms time resolution. References [1] X. M. Chen et al. Phys. Rev. Lett. 117, 167001 (2016) [2] V. Thampy et al. Phys. Rev. B 95, 241111 (2017) [3] X. M. Chen et al. Nat Commun. 10 1435 (2019) [4] X. M. Chen et al. under review, arXiv:1809.05656 [cond-mat.mes-hall]
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NT/RIKEN Seminar
"D meson mixing via dispersion relation"
Presented by Hsiang-nan Li, National Center for Theoretical Sciences, Physics Division, Taiwan
Friday, June 14, 2019, 2 pm
Building 510, CFNS Room 2-38Hosted by: Niklas Mueller
In this talk I will explain how to calculate the D meson mixing parameters x and y in the Standard Model. Charm physics is notoriously difficult, because most effective theories and perturbation theories do not apply well. I propose to study the D meson mixing via a dispersion relation, which relates low mass dynamics to high mass one. Taking heavy quark results as inputs in the high mass region, we obtain x and y consistent with experimental data at least in order of magnitude.
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Physics Department Summer Lecture Series
"The Little Neutral One"
Presented by Mary Bishai, BNL
Friday, June 14, 2019, 12:30 pm
Small Seminar Room, Bldg. 510Hosted by: Mary Bishai
In the past 50 years, the study of neutrinos, the lightest, yet most abundant of the known elementary particles has revealed cracks in the Standard Model of Particle Physics. Could neutrinos explain the matter anti-matter asymmetry in our Universe? To answer these questions we need to better understand the properties of these elusive polymorphs. I will present a brief history of the neutrino, what we have learnt so far about it, and what we hope to learn in the next couple of decades from some of the most ambitious experiments in particle physics.
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NSLS-II Friday Lunchtime Seminar
"High resolution strain measurements and phase discrimination in solid solutions using X-Ray Diffuse Multiple Scattering (DMS)"
Presented by Gareth Nisbet, Diamond Light Source, United Kingdom
Friday, June 14, 2019, 12 pm
NSLS-II Bldg. 743 Room 156Hosted by: Ignace Jarrige
DMS is a new high resolution scattering technique which manifests as diffraction lines impinging on the detector plane, similar to Kikuchi lines or Kossel lines. I will explain how multiple intersections from coplanar and non-coplanar reflections can be used for phase discrimination in multi-phasic systems by following a simple reductive procedure. The methods will be demonstrated using data from complex PMN-PT and PIN-PMN-PT ferroelectric solid solutions. I will also show how convolutional neural networks are being applied to DMS data for phase discrimination.
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Particle Physics Seminar
"Argon Capture Experiment at DANCE (ACED)"
Presented by Jingbo Wang, UC Davis
Thursday, June 13, 2019, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Chao Zhang
Liquid argon is becoming a popular medium for particle detection, with applications ranging from low-background dark matter searches to high-energy neutrino detection. Because neutrons may represent both an important source of background and a product of signal events, a good understanding of their interactions in argon is a requirement for precision physics measurements. Despite being one of the most basic quantities needed to describe low energy neutron transport, the thermal neutron capture cross section on argon remains poorly understood, with the existing activation measurements showing significant disagreements. To resolve these disagreements, the Argon Capture Experiment at DANCE (ACED) collaboration has performed a differential measurement of the 40Ar(n, gamma)41Ar cross section using a time of flight neutron beam and the Detector for Advanced Neutron Capture Experiments (DANCE), a ∼4pi gamma spectrometer at Los Alamos National Laboratory. A fit to the differential cross section from 0.015-0.15eV, assuming a 1/v energy dependence, yields sigma(2200)=673+-26 (stat.) +- 59(sys.) mb. During this talk, I will introduce the DUNE experiment before focusing on the importance of neutrons in liquid argon detectors. I will then present the ACED experiment and the use of neutrons as a detector calibration method.
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Physics Colloquium
"High energy atmospheric neutrinos: connections between laboratory experiments and cosmic rays"
Presented by Mary Hall Reno, University of Iowa
Tuesday, June 11, 2019, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Milind Diwan
The IceCube Neutrino Observatory's measurement of a diffuse flux of neutrinos from astrophysical sources has opened a new era in high energy astroparticle physics. Neutrinos produced by cosmic ray interactions in the atmosphere are the main background to the astrophysical neutrino flux. At these high energies, data from the Large Hadron Collider experiments on heavy flavor production can be used to narrow the uncertainties in the background predictions at the highest energies. Our evaluation of the atmospheric neutrino flux from charm will be used to illustrate how collider physics results are connected to cosmic ray physics in this context.
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Physics Department Summer Lecture Series
"The Anomalous Magnetic Moment of the Muon and the Standard Model of Particle Physics"
Presented by William Morse, BNL
Tuesday, June 11, 2019, 12:30 pm
Small Seminar Room, Bldg. 510Hosted by: Mary Bishai
At the end of this lecture, you will know: What is anomalous about the magnetic moment of the muon. What is the magnetic moment of the muon. What is the muon. Why Bohr said "Anyone who thinks they understand Quantum Mechanics, and is not deeply disturbed by it, doesn't understand Quantum Mechanics." What the Standard Model Theorists have to fear from the anomalous magnetic moment of the muon.
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Physics Department Summer Lecture Series
"Visible and Invisible Clues for New Physics"
Presented by Hooman Davoudiasl, BNL
Friday, June 7, 2019, 12:30 pm
Small Seminar Room, Bldg. 510Hosted by: Mary Bishai
In this presentation, we will briefly describe the main elements of the Standard Model of particle physics. This theory, together with General Relativity, provides a precise description of a vast array of experimental and observational data, from microscopic to astronomical scales. However, solid empirical evidence and conceptual clues lead us to expect that this "standard" picture is incomplete. We will discuss some of the key reasons for this expectation.
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NSLS-II Friday Lunchtime Seminar
"Status and perspective of high-energy automotive batteries"
Presented by Richard Schmuch, University of Munster, Germany
Friday, June 7, 2019, 12:30 pm
NSLS-II Bldg. 743 Room 156Hosted by: Ignace Jarrige
This presentation gives an overview of the materials, performance requirements and cost of current automotive traction batteries based on Li-ion technology. It also includes important aspects related to electromobility, such as its sustainability and energy efficiency. As current Li-Ion batteries with intercalation-type active materials are approaching their physicochemical energy density limit of roughly 300 Wh/kg or 800 Wh/L, alternative technologies such as lithium-metal based all-solid-state batteries (ASSBs) currently intensively studied, which promise an energy density of up to 1000 Wh/L. The potential and challenges of this and other post Li-ion batteries (e.g. Dual-Ion, Mg-Ion, Li-Sulphur) are discussed and also compared by systematic bottom-up energy density calculations. Through a step-by-step analysis from theoretical energy content at the material level to practical energies at the cell level, the individual advantages and shortcomings of the studied battery types are elucidated. Literature: (1) Schmuch, R.; Wagner, R.; Hörpel, G.; Placke, T.; Winter, M. Performance and Cost of Materials for Lithium-Based Rechargeable Automotive Batteries. Nat. Energy 2018, 3 (4), 267–278. (2) Betz, J.; Bieker, G.; Meister, P.; Placke, T.; Winter, M.; Schmuch, R. Theoretical versus Practical Energy: A Plea for More Transparency in the Energy Calculation of Different Rechargeable Battery Systems. Adv. Energy Mater. 2018, 1803170, 1803170. (3) Placke, T.; Kloepsch, R.; Dühnen, S.; Winter, M. Lithium Ion, Lithium Metal, and Alternative Rechargeable Battery Technologies: The Odyssey for High Energy Density. J. Solid State Electrochem. 2017, 1–26. (4) Meister, P.; Jia, H.; Li, J.; Kloepsch, R.; Winter, M.; Placke, T. Best Practice: Performance and Cost Evaluation of Lithium Ion Battery Active Materials with Special Emphasis on Energy Efficiency. Chem. Mater. 2016, 28 (20), 7203-7217
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Condensed-Matter Physics & Materials Science Seminar
"Probing quantum materials with multiple spectroscopic techniques"
Presented by Eduardo H. da Silva Neto, University of California, Davis
Thursday, June 6, 2019, 1:30 pm
ISB - Bldg. 734Hosted by: Robert Konik
Resonant X-ray Scattering (RXS), Scanning Tunneling Spectroscopy (STS) and Angle-Resolved Photo-Emission Spectroscopy (ARPES) measurements have been at the forefront of several advances in the studies of quantum materials. Our group specializes in these techniques, looking to leverage their combination to the study of quantum materials. I will discuss two projects where we have used these state-of-the-art techniques to study high-temperature superconductors and topological materials. Charge order has now been ubiquitously observed in cuprate high-temperature superconductors. However, it remains unclear if the charge order is purely static or whether it also features dynamic correlations. I will discuss a polarization-resolved soft x-ray inelastic RXS experiment with unprecedented resolution that demonstrates the existence of a coupling between dynamic magnetic and charge-order correlations in the electron-doped cuprate Nd2−xCexCuO4 [1-3]. I will also discuss a combined ARPES-STS study of the topological material Hf2Te2P. Similar to the reports by H. Ji, et al. on Zr2Te2P [4], band structure calculations and ARPES by Hosen et al. [5] also suggest multiple topological surface states in Hf2Te2P. However, some topological surface states still lacked direct spectroscopic evidence due the inability of ARPES experiments to probe the unoccupied band structure. Using the combination of STS and ARPES with surface K-doping, we probe the unoccupied band structure of Hf2Te2P and demonstrate the presence of multiple surface states with a linear Dirac-like dispersion, consistent with the predictions from previously reported band structure calculations [6]. [1] E. H. da Silva Neto, et al. Science 347, 282 (2015). [2] E. H. da Silva Neto, et al. Science Advances 2 (8), e1600782 (2016). [3] E. H. da Silva Neto, et al. Physical Review B, Rapid Communication 98, 161114(R) (2018). [4] H. Ji, et al. Physical
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Condensed-Matter Physics & Materials Science Seminar
"Mega-electron-volt ultrafast electron diffraction at SLAC National Accelerator Laboratory"
Presented by Xiaozhe Shen, SLAC National Accelerator Laboratory
Monday, June 3, 2019, 2 pm
Bldg. 480, Conference RoomHosted by: Jing Tao
Ultrafast electron diffraction (UED) is a transformative tool for probing atomic structural dynamics in ultrafast science to understand the correlation between materials' structure and their functionalities, with the ultimate goal of controlling energy and matter. The advent of high-brightness relativistic electron beams from photocathode radio frequency (RF) gun provides a great opportunity to push the resolving power of UED onto atomic length and time scales. With the expertise in electron beam physics and ultrafast laser technology, SLAC has dedicated enormous efforts to develop a world-leading UED using mega-electron-volt (MeV) electron beams since 2014. Over the years, SLAC MeV UED has achieved great instrument performance and delivered numerous scientific outcomes for ultrafast science. In 2019, SLAC MeV UED has officially transformed into a user facility. In this talk, performance of SLAC MeV UED will be reviewed, including characterization of the instrument resolution and machine stability. The unique capabilities of SLAC MeV UED to accommodate various sample environments for a broad range of scientific interests, including condense matter physics and chemical science, will be presented, with highlighted scientific results. Research and development efforts to improve the performance of SLAC MeV UED will be discussed.
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Particle Physics Seminar
"Dark matter in the cosmos-The Hunt to Find it in the Laboratory"
Presented by Ioannis (J.D.) Vergados
Friday, May 31, 2019, 11 am
Small Seminar Room, Bldg. 510Hosted by: Milind Diwan
There is plenty of evidence at all scales (galaxies, cluster of galaxies, cosmological distances) that most of the energy content of the universe is of unknown nature, i.e, 70% is dark energy and 25% dark matter. Only 5% is made up of matter of known nature, in atoms, in stars, in planets etc, constituents predicted by the standard model. Thus unraveling the nature of the dominant components and, in particular, of dark matter is one of the most important open problems in science. This nature can only be understood by the direct detection of its constituents in the laboratory. This can be achieved, if there exists a week interaction, much stronger than gravity, between the dark matter and ordinary matter. The constituents are supposed to have a mass and are called WIMPs (weakly interacting massive particles). We have no idea what this mass is, but from the rotational curves we know that the constituents must be non relativistic, regardless of the size of their mass. The experimental techniques for the direct detection crucially depend on the assumed WIMP mass. Historically the first searches assumed WIMP masses of many GeV and, therefore, heavy nuclear targets were favored. Thus the hunt for DM began and evolved into a multi-pronged and interdisciplinary enterprise, combining cosmology and astrophysics, particle and nuclear physics as well as detector technology, which will be reviewed. Since the WIMP energy is in the keV region, the nucleus cannot be excited and only the nuclear recoil can be measured. As a result, unfortunately, the signal cannot be easily distinguished from backgrounds. After thirty years of intensive work against formidable backgrounds by a lot of large experimental teams, no dark matter has been found. Impressive limits on the nucleon cross section have, however, been obtained. Extension of these searches to GeV or sub-GeV WIMPs is also been considered using light nuclear targets. It may very w
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Particle Physics Seminar
"Latest oscillation results from the NOvA experiment"
Presented by Diana Patricia Mendez, University of Sussex
Thursday, May 30, 2019, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Elizabeth Worcester
NOvA is a long-baseline neutrino oscillation experiment measuring $\nu_{\mu}$ disappearance and $\nu_e$ appearance within the NuMI beam from Fermilab. The experiment uses a Near and a Far Detector placed 810 km away from each other and at 14 milliradians off the beam-axis resulting in an observed energy spectrum that peaks at 2 GeV, close to the oscillation maximum. A combined $\bar{\nu}_{\mu}$ + $\nu_{\mu}$ disappearance, and $\bar{\nu}_{e}$ + $\nu_{e}$ appearance result will be presented including NOvA's first collected anti-neutrino data for a total exposure of $16\times10^{20}$ protons-on-target. In addition to an increased exposure, an upgraded analysis has enable the experiment to set new limits to the allowed regions for $\Delta m^2_{32}$ and sin$^2\theta_{23}$ and make a measurement of $\Delta m^2_{32}$ among the world's best.
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RIKEN Lunch Seminar
"Applications of machine learning to computational physics"
Presented by Dr Akio Tomiya, RBRC
Thursday, May 30, 2019, 12 pm
Building 510, Room 2-160Hosted by: Yuta Kikuchi
In this talk, I would like to talk about my works with machine learning. I plan to introduce my works which related to lattice QCD research: detection of phase transition in classical spin systems [arXiv 1609.09087, 1812.01522], configuration generation [1712.03893 + some]
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Environmental & Climate Sciences Department Seminar
"The Influence of Aerosol Chemical Composition, Morphology, and Phase State on Water and Ice Cloud Particle Formation"
Presented by Yue Zhang, North Carolina State, MIT, and Aerodyne
Thursday, May 30, 2019, 11 am
Large Conference Room, Bldg. 490Hosted by: Ernie Lewis
Aerosols and clouds effect Earth's radiative balance, and aerosol-cloud interactions are major sources of uncertainties in predicting future climate. The climate effects of water and ice cloud particles formed from atmospheric particulate matter are not well understood due to the complex physical and chemical properties of these aerosols. Measurements from fixed sites and field campaigns have shown that organic aerosols (OA) dominate the non-refractory aerosols in the free troposphere where clouds typically form, and cloud water and ice cloud residue both show the presence of organic materials. Despite the abundance of OA, their effects on both cloud condensation nuclei (CCN) and ice nucleation (IN) are not fully understood and even controversial. To probe into these issues, the CCN and IN properties of complex inorganic-organic aerosol mixtures that simulate ambient conditions were measured with a cloud condensation nuclei counter (CCNC, DMT, Inc.) and a spectrometer for ice nucleation (SPIN, DMT, Inc.) at a variety of laboratory conditions. Our studies suggest that the composition of the organic-containing aerosols, as well as their morphology and phase state, jointly impact their cloud forming potential. The results highlight the importance of combining aerosol physical and chemical properties to accurately understand cloud particle formation processes and their implications on the climate.
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Nuclear Physics Seminar
"Examining hydrodynamical modelling of the QGP through dilepton radiation"
Presented by Gojko Vujanovic, Wayne State University
Tuesday, May 28, 2019, 11 am
Small Seminar Room, Bldg. 510Hosted by: Rongrong Ma
Recent viscous hydrodynamical studies at the Relativistic Heavy-Ion Collider (RHIC) and the Large Hadron Collider (LHC), show that bulk viscosity plays an important role in their phenomenological description. A temperature-dependent bulk viscosity in the hydrodynamical evolution of the medium can modify the development of the hydrodynamic momentum anisotropy differently in the high- and low-temperature regions. Thus, anisotropic flow coefficients of various particle species are affected differently depending where their surface of last scattering lies. For the case of hadronic observables, they are predominantly sensitive to low temperature regions, while electromagnetic radiation is emitted at all temperatures. Therefore, bulk viscosity should affect electromagnetic radiation differently than hadron emission. The effects of bulk viscosity on one of the electromagnetic probes, namely photons, has already been investigated. The same statement holds true for hadrons. The goal of this presentation is to study how dilepton production, the other source of electromagnetic radiation, gets modified owing to the presence of bulk viscosity at RHIC and LHC energies. With calculations at different collision energies, comparisons in the dilepton signal can be made and more robust conclusions regarding the role of bulk viscosity in high energy heavy-ion collisions can be drawn. Dilepton radiation from the dilute hadronic sector of the medium, which are radiated in addition to dileptons emitted during the hydrodynamical evolution, will also be included to ascertain whether interesting dynamics induced by bulk viscosity may have observable consequences. To complete that investigation, particular attention will be given to how the $\rho(770)$ meson, and its subsequent dilepton decay, is calculated at the end of the hydrodynamical simulation.
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NT/RIKEN Seminar
"Pieces of the Puzzle: Reaching QCD on Quantum Computers"
Presented by Henry Lamm, UMD
Friday, May 24, 2019, 2 pm
Building 510, CFNS Seminar Room 2-38Hosted by: Niklas Mueller
The advent of quantum computing for scientific research presents the possibility of calculating time-dependent observables like viscosity and parton distributions from QCD. In order to utilize this new tool, a number of theoretical and practical issues must be addressed related to efficiently digitize, initialize, propagate, and evaluate quantum field theory. In this talk, I will discuss a number of projects being undertaken by the NuQS collaboration to realize calculations on NISQ era and beyond quantum computers.
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CFNS Seminar
"Effect of non-eikonal corrections on two particle correlations"
Presented by Tolga Altinoluk, National Centre for Nuclear Research, Warsaw, Poland
Thursday, May 23, 2019, 4 pm
Building 510, CFNS Room 2-38Hosted by: Andrey Tarasov
We will discuss the non-eikonal effects on gluon production in pA collisions that originate from the finite longitudinal width of the target. We will then consider the dilute target limit, and discuss the single and double inclusive gluon production cross section in pp collisions. We will show that non-eikonal corrections break the accidental symmetry of the CGC and give rise to non-vanishing odd azimuthal harmonics.
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Condensed-Matter Physics & Materials Science Seminar
"In situ imaging of gold nanocrystals during the CO oxidation reaction studied by Bragg Coherent Diffraction Imaging"
Presented by Ana Flavia Suzana, Brazilian Association of Synchrotron Light Technology-ABTLUS, Brazil
Thursday, May 23, 2019, 1:30 pm
ISB Bldg. 734, Conf. Rm. 201 (upstairs)Hosted by: Ian Robinson
The fundamental aim of heterogeneous catalysis research is to understand mechanisms at the nanoparticle level, and then to design and synthesize catalysts with desired active sites. In this regard, the in situ/operando characterization of defects is crucial as they are preferential catalytic sites for the reaction occurrence. In this seminar I will talk about the main part of the work developed during my PhD: the investigation of the morphology and structure evolution of gold nano-catalysts supported on titanium dioxide. Those catalytic materials were evaluated for the model CO oxidation reaction, chosen for its environmental relevance and "simplicity" to be reproducible within our X-ray imaging study. We used the Bragg Coherent Diffraction Imaging technique to follow in situ the 3D morphology changes under catalytic reaction conditions. We correlated the 3D displacement field and strain distribution of the gold nanoparticles to the catalytic properties of the material. In particular, for a 120 nm gold nanoparticle, we quantified under working conditions the adsorbate-induced surface stress on the gold nanocrystal, which leads to restructuration and defects identified as a nanotwin network.
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RIKEN Lunch Seminar
"Complex saddle points of path integrals"
Presented by Semeon Valgushev, BNL
Thursday, May 23, 2019, 12 pm
Building 510, Room 2-160Hosted by: Yuta Kikuchi
In this talk, we discuss the physical role of complex saddle points of path integrals. In the first case study, we analyze saddle point structure of two-dimensional lattice gauge theory represented as Gross-Witten-Wadia unitary matrix model. We find that non-perturbative physics in the strong coupling phase can be understood in terms of new family of complex saddle points those properties are connected to resurgent structure of the 1/N expansion. In the second case study, we discuss the sign problem in fermionic systems at finite density and the possibility to alleviate it with the help of defomations of integration contour into complex space on the example of two-dimensional Hubbard model.
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Chemistry Department Seminar
"Designing Dopants to Shield Anion Electrostatics in Doped Conjugated Polymers to Obtain Highly Mobile and Delocalized Carriers"
Presented by Taylor Aubry, UCLA
Thursday, May 23, 2019, 11 am
Room 300, 3rd Floor - Chemistry Bldg. 555Hosted by: Matthew Bird
Doping conjugated polymers is an effective way to tune their electronic properties for thin-film electronics applications. Chemical doping of semiconducting polymers involves the introduction of a strong electron acceptor or donor molecule that can undergo charge transfer (CT) with the polymer. The CT reaction creates electrical carriers on the polymer chain (usually positive polarons a.k.a. holes) while the dopant molecules remain in the film as counterions. Undesirably, strong electrostatic attraction from the anions of most dopants will localize the polarons and reduce their mobility. We employ a new strategy utilizing substituted icosahedral dodecaborane (DDB) clusters as molecular dopants for conjugated polymers. DDBs provide a unique system in which the redox potential of the dopant can be rationally tuned via modification of the substituents without significant change to the size or shape of the dopant molecule. These clusters allow us to disentangle the effects of energetic offset on the production of free and trapped carriers in DDB-doped poly-3-hexylthiophene (P3HT) films. We find that by designing our cluster to have a high redox potential and steric protection of the core-localized electron density, highly delocalized polarons with mobilities equivalent to films doped with no anions present are obtained.1 P3HT films doped with these boron clusters have conductivities and polaron mobilities roughly an order of magnitude higher than films doped with conventional small-molecule dopants such as 2,3,5,6-tetrafluoro-7,7,8,8- tetracyanoquinodimethane (F4TCNQ). The spectral shape of the IR-region absorption for our DDB-doped polymer film closely matches the calculated theoretical spectrum for the anion at infinite distance from the polaron.2 We therefore conclude that these DDB clusters are able to effectively spatially separate the counterion. Moreover, nearly all DDB-produced carriers are free, while it has been shown that small m
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C-AD Accelerator Physics Seminar
"High-Level Software Development for the CLARA FEL Test Facility"
Presented by Dr. James Jones, Daresbury Laboratory
Wednesday, May 22, 2019, 3 pm
Bldg. 911B, Second Floor, Large Conf. Rm., Rm. A2Hosted by: Steve Peggs
CLARA is a low-energy test facility for advanced FEL physics and beam-driven novel acceleration techniques. As part of the facility we have planned for an advanced integrated system for high-level software development and online-model based on C++ and python interfaces. An overview of the CLARA facility and recent experimental results will be presented along with a description and current status of the HLS middle-layer and online-model. Future plans for CLARA will also be presented.
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Nuclear Physics Seminar
"Future opportunities for a small-system scan at RHIC"
Presented by Jiangyong Jia
Tuesday, May 21, 2019, 11 am
Small Seminar Room, Bldg. 510Hosted by: Rongrong Ma
The observation of multi-particle azimuthal correlations in high-energy small-system collisions has led to intense debate on its physical origin between two competing theoretical scenarios: one based on initial-state intrinsic momentum anisotropy (ISM), the other based on final-state collective response to the collision geometry (FSM). To complement the previous scan of asymmetric collision systems (p+Au, d+Au and He+Au), we propose a scan of small symmetric collision systems at RHIC, such as C+C, O+O, Al+Al and Ar+Ar at sqrt{s_NN} = 0.2 TeV, to further disentangle contributions from these two scenarios. These symmetric small systems have the advantage of providing access to geometries driven by the average shape of the nuclear overlap, compared to fluctuation-dominant geometries in asymmetric systems. A transport model is employed to investigate the expected geometry response in the FSM scenario. Different trends of elliptic flow with increasing charge particle multiplicity are observed between symmetric and asymmetric systems, while triangular flow appears to show a similar behavior. Furthermore, a comparison of O+O collisions at sqrt{s_NN} = 0.2 TeV and at sqrt{s_NN} =2.76−7 TeV, as proposed at the LHC, provides a unique opportunity to disentangle the collision geometry effects at nucleon level from those arising from subnucleon fluctuations.
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NSLS-II Friday Lunchtime Seminar
"MAXPD: Multi-Anvil X-ray Powder Diffraction — COMPRES Partner User Program for High Pressure Studies at 28-ID-2-D"
Presented by Matthew L. Whitaker, Stony Brook University
Friday, May 17, 2019, 12 pm
NSLS-II Bldg. 743 Room 156Hosted by: Ignace Jarrige
MAXPD is the downstream endstation of XPD, an insertion device beamline at Sector 28 (28-ID-2-D) of NSLS-II. The MAXPD endstation and General User Program are sponsored by the COnsortium for Materials Properties Research in Earth Sciences (COMPRES). MAXPD has an 1100-ton hydraulic press installed, which is equipped with a unique DT-25 pressure module that can be swapped out for a more standard D-DIA module as desired. MAXPD makes use of the world-class monochromatic beam available at XPD (usually ~67 keV), with which we collect both angular dispersive X-ray diffraction data and X-radiographic imaging. The first General User experiments took place in March 2018. Final Science Commissioning beamtime took place in August of last year, and the full General User program for MAXPD began in the 2018-3 cycle. In this seminar, I will give an overview of the science drivers behind the development of the endstation, some of its unique capabilities, some representative results from recent experiments conducted over the last two cycles at MAXPD, and where we are looking to go as we look to the future.
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RIKEN Lunch Seminar
"Electric dipole moments in the era of the LHC"
Presented by Jordy de Vries, University of Massachusetts Amherst, Riken BNL
Thursday, May 9, 2019, 12 pm
Building 510, Room 2-160Hosted by: Yuta Kikuchi
The search for an understanding of fundamental particle physics that goes beyond the Standard Model (SM) has grown into a worldwide titanic effort. Low-energy precision experiments are complementary to collider searches and, in certain cases, can even probe higher energy scales directly. However, the interpretation of a potential signal, or lack thereof, is complicated because of the non-perturbative nature of low-energy QCD. I will use the search for electric dipole moments (EDMs), which aims to discover beyond-the-SM CP violation, as an example to illustrate these difficulties and how they can be overcome by combining (chiral) effective field theory and lattice QCD. I discuss how EDM experiments involving complex systems like nucleons, nuclei, atoms, and molecules constrain possible CP-violating interactions involving the Higgs boson, how these constraints match up to direct LHC searches, and the relevance of and strategies for the improvement of the hadronic and nuclear theory.
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Environmental & Climate Sciences Department Seminar
"High-throughput field phenotyping of photosynthetic capacity using hyperspectral imaging"
Presented by Katherine Meacham, Univ. of Illinois
Thursday, May 9, 2019, 11 am
Large Conference Room, Bldg. 490Hosted by: Angie Burnett
Improved photosynthetic rates have been shown to increase crop biomass, making improved photosynthesis a focus for driving future grain yield increases. Improving the photosynthetic pathway offers opportunity to meet food demand, but requires high throughput measurement techniques to detect photosynthetic variation in natural accessions and transgenically improved plants. Gas exchange measurements are the most widely used method of measuring photosynthesis in field trials but this process is laborious and slow, and requires further modeling to estimate meaningful parameters and to upscale to the plot or canopy level. In field trials of tobacco with modifications made to the photosynthetic pathway, we infer key photosynthetic parameters from imaging spectroscopy using a partial least squares regression technique. We used two hyperspectral cameras with resolution 2.1nm in the visible range and 4.9nm in the NIR. Ground-truth measurements from leaf-level photosynthetic gas exchange, full-range (400-2500nm) hyperspectral reflectance and extracted pigments support the model. The results from a range of wild-type cultivars and from genetically modified germplasm offer a high-throughput screening tool for crop trials aimed at identifying increased photosynthetic capacity.
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Physics Colloquium
"Mu*STAR Accelerator-Driven Subcritical Molten-Salt All-Purpose non-Nuclear Reactor"
Presented by Rolland Johnson, Muons Inc.
Tuesday, May 7, 2019, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: George Redlinger
The Mu*STAR BHAG[1] is: To make superconducting RF accelerators so powerful and efficient that they make enough neutrons to produce nuclear energy for electricity or for process heat at less cost than from wind, solar, or natural gas, without weapons proliferation legacies of enrichment and chemical reprocessing, by burning unwanted nuclear materials. The arguments are presented to support that such a goal is possible in the near future. [1] BHAG: Big Hairy Audacious Goal, from "Built to Last: Successful Habits of Visionary Companies" by Jim Collins and Jerry Porras (2004)
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NT/RIKEN Seminar
"Relativistic Hydrodynamic Fluctuations"
Presented by Gokce Basar, UiC
Friday, May 3, 2019, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Niklas Mueller
We present a general systematic formalism for describing dynamics of fluctuations in an arbitrary relativistic hydrodynamic flow, including their feedback (known as long-time hydrodynamic tails) in a deterministic way. The fluctuations are described by two-point equal-time correlation functions. We introduce a definition of equal time in a situation where the local rest frame is determined by the local flow velocity, and a method of taking derivatives and Wigner transforms of such equal-time correlation functions, which we call confluent. The Wigner functions satisfy evolution equations that describes the relaxation of the out-of-equilibrium modes. We find that the equations for confluent Wigner functions nontrivially match with the kinetic equation for phonons propagating on an arbitrary background, including relativistic inertial and Coriolis forces due to acceleration and vorticity of the flow. We also describe the procedure of renormalization of short-distance singularities which eliminates cutoff dependence, allowing efficient numerical implementation of these equations.
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Special Particle Physics Seminar
"Observation of CP violation in charm decays"
Presented by Angelo Di Canto, BNL
Friday, May 3, 2019, 11 am
Small Seminar Room, Bldg. 510Hosted by: Chao Zhang
The existence of CP violation in the decays of strange and beauty mesons is well established experimentally by numerous measurements. By contrast, CP violation in the decays of charm particles has so far escaped observation. This seminar reports on the first observation of CP violation in charm decays thought the measurement of the difference between the time-integrated CP asymmetries in D0 -> K- K+ and D0 -> pi- pi+ decays. The measurement has been performed using the full data set of proton-proton collisions collected by LHCb in 2011-2018, which corresponds to an integrated luminosity of 9fb-1. In addition, a brief overview of recent measurements of mixing and mixing-induced CP violation in charm mesons at LHCb is also presented.
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Particle Physics Seminar
"Dark Matter Searches with the ATLAS Detector at the LHC"
Presented by Arely Cortes Gonzalez, CERN
Thursday, May 2, 2019, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Michael Begel
The presence of a non-baryonic dark matter component in the Universe is inferred from the observation of its gravitational interaction. If dark matter interacts weakly with the Standard Model it would be produced at the LHC, escaping the detector and leaving a large missing transverse momentum as their signature. The ATLAS detector has developed a broad and systematic search program for dark matter production in LHC proton-proton collisions. The results of these searches on the 13 TeV data, their interpretation, and the possible evolution of the search program will be presented.
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RIKEN Lunch Seminar
"The Chiral Qubit: quantum computing with chiral anomaly"
Presented by Dmitri Kharzeev, Stony Brook University and BNL
Thursday, May 2, 2019, 12 pm
Building 510, Room 2-160Hosted by: Yuta Kikuchi
The quantum chiral anomaly enables a nearly dissipationless current in the presence of chirality imbalance and magnetic field – this is the Chiral Magnetic Effect (CME), observed recently in Dirac and Weyl semimetals. We propose to utilize the CME for the design of qubits potentially capable of operating at THz frequency, room temperature, and the coherence time to gate time ratio of about 10^4 . The proposed "Chiral Qubit" is a micron-scale ring made of a Weyl or Dirac semimetal, with the |0> and |1> quantum states corresponding to the symmetric and antisymmetric superpositions of quantum states describing chiral fermions circulating along the ring clockwise and counter-clockwise. A fractional magnetic flux through the ring induces a quantum superposition of the |0> and |1> quantum states. The entanglement of qubits can be implemented through the near-field THz frequency electromagnetic fields.
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Nuclear Physics Seminar
"Reviewing the AGS Heavy Ion Program and Looking Forward to the Fixed-Target Program at STAR"
Presented by Prof. Daniel Cebra, UC Davis
Tuesday, April 30, 2019, 11 am
Small Seminar Room, Bldg. 510Hosted by: Rongrong Ma
In the 1980's and 90's the AGS initiated a heavy-ion beam program with both silicon and gold beams. A suite of dedicated experiments established the systematics for production of light charged particles, strangeness, light nuclei, and anti-particles, as well as systematics for flow and femtoscopy. Those experiments established the design of the RHIC detectors and trained the personnel who would become leaders in the RHIC program. Recently, there has been renewed interest in the energy region covered by the AGS heavy-ion program. New facilities are being built Germany and Russia and proposed in Japan and China. And a conclusion of the first beam energy scan at RHIC was that it would be necessary to revisit the AGS energy range by installing a fixed-target within the STAR experiment. This talk will review key results from the AGS heavy-ion program, and those to results from the STAR fixed-target test runs, and outline the proposed physics program.
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Particle Physics Seminar
""Measure what is measurable and make measurable what is not so - Uncover new physics with bosons at the LHC and upgrades of the CMS detector to maximize the discovery potential""
Presented by Mia Liu, FNAL
Monday, April 29, 2019, 11 am
Small Seminar Room, Bldg. 510Hosted by: Alessandro Tricoli
The Standard Model describes the building blocks of matter and their interactions. It has been tested extensively with experimental data and found to be incredibly successful in describing nature. Discovering the Higgs boson in 2012 at the LHC completed the picture of the SM. The LHC is at the forefront of directly searching for new physics which is Beyond-Standard-Model (BSM), and I will discuss searches for supersymmetric partners of the electroweak bosons, as well as measurement of an extremely rare process with three WWW bosons as stringent tests of the SM. I will also discuss the instrumentation which enables such studies. The discussion includes the recently completed CMS Phase-1 pixel upgrade, as well as the R&D studies towards solving the future trigger and computing challenges using innovative machine learning approaches in future high energy experiments.
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Particle Physics Seminar
"Searching for Higgs Pair Production at the LHC"
Presented by Elizabeth Brost, Northern Illinois University
Thursday, April 25, 2019, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Alessandro Tricoli
Since the discovery of the Higgs boson in 2012, the particle physics community at the Large Hadron Collider (LHC) has been hard at work studying its properties, and comparing them to the predictions of the Standard Model (SM), including the couplings of the Higgs boson to itself and to other particles. The Higgs self-coupling can be measured directly in the Higgs pair production process, and will provide insight into the nature of electroweak symmetry breaking. In the SM, the di-Higgs cross section in proton-proton collisions is very small. However, a wide range of beyond-the-SM models predict enhancements to the di-Higgs production rate, which motivates searching for di-Higgs production even now, when the SM cross section is too small to measure in the current LHC dataset. Looking forward, the LHC Run 3 and HL-LHC will bring a new set of challenges, including more proton-proton collisions per bunch crossing. Extracting rare physics signatures from this busier environment will be difficult for the current ATLAS trigger system. In this talk, I will present current and future ATLAS searches for hh production using a variety of final states, and discuss the use of future track triggers in upgrades to the ATLAS trigger system.
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NT/RIKEN Seminar
"Parton distributions in Euclidean space"
Presented by Anatoly Radyushkin, ODU/JLab
Friday, April 19, 2019, 2 pm
Building 510, CFNS Room 2-38Hosted by: Niklas Mueller
To extract parton distributions from the lattice simulations, one needs to consider matrix elements M(z,p) of bilocal correlators of parton fields [generically written as φ(0)φ(z)] at spacelike separations z=(0,0,0,z_3). A transition to PDFs may be proceeded by taking a Fourier transform either with respect to z_3 for fixed p_3 (which gives X. Ji's quasi-PDFs), or with respect to the Lorentz-invariant variable ν=-(zp) for fixed values of another Lorentz invariant z^2 [which results in pseudo-PDFs].These functions are interesting on their own, and I will discuss, in the continuum case, their general properties, the connection between the two types of functions, and their relation with the usual light-cone PDFs. I will outline the algorithm of extracting the PDFs through the use of the so-called "reduced Ioffe-time distributions",and illustrate this pseudo-PDF-oriented approach on the example of exploratory lattice simulations performed by Orginos et al.
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Particle Physics Seminar
"Dissecting the Higgs boson with ATLAS and leptons"
Presented by Quentin Buat, CERN
Thursday, April 18, 2019, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Alessandro Tricoli
Using data taken during the first years of the LHC Run2, ATLAS has firmly established the coupling of the Higgs boson to the tau lepton, thus directly confirming the existence of leptonic Yukawa interactions. In this talk, I will present the cross-section measurements performed by ATLAS in the di-tau final state with a partial Run2 dataset and discuss the prospects of the analysis with the full Run2 dataset and beyond. I will also discuss the status of the search for the muonic Yukawa interaction.
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Condensed-Matter Physics & Materials Science Seminar
""Superconductivity and magnetism at ferroelectric critical point""
Presented by Alexander Balatsky, UConn Nordita
Thursday, April 18, 2019, 1:30 pm
ISB Bldg. 734 Conf. Rm. 201 (upstairs)Hosted by: Ilya Drozdov
It is well established that multiple entangled orders emerge in quantum materials at criticality: eg superconducting states develop in the vicinity of magnetic phases. I will make the case that similar phenomena occur in quantum paraelectrics. Recent observations of strain and O18 isotope substitution in doped STO support the view of the key role critical ferroelectric fluctuations play in producing superconductivity. Looking beyond superconductivity, I will illustrate how quantum ferroelectric fluctuations can induce magnetic fluctuations due to recently proposed phenomenon of dynamic multiferroicity.
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Environmental & Climate Sciences Department Seminar
"Using High-Resolution Observations to Improve a Low-Resolution Global Climate Model"
Presented by Greg Elsaesser, NASA GISS
Thursday, April 18, 2019, 11 am
Large Conference Room, Bldg. 490Hosted by: Mike Jensen
This talk will begin with an overview of recent development in the representation of deep convection in the NASA Goddard Institute for Space Studies (GISS) General Circulation Model (GCM). Global satellite remote sensing products are important references for continual GCM development and evaluation, but such products often provide data at coarse temporal and/or spatial resolutions, thus making it difficult to conceptualize and evaluate "process representations" in a GCM. I will discuss the various approaches I am taking to average global satellite retrievals in new ways, coincident with efforts to use new DOE/ARM observations, to derive composite high-resolution evolutions of deep convection and the nearby environment. These depictions will not only inform future development, but they are also crucial for ensuring that recent improved mean-state representations are not the result of errors cancelling at the process level.
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Nuclear Physics Seminar
"Recent Results from COMPASS"
Presented by Ana-Sofia Nunes, BNL
Tuesday, April 16, 2019, 11 am
Small Seminar Room, Bldg. 510Hosted by: Oleg Eyser
COMPASS is a fixed target experiment at the CERN SPS that has been collecting data since 2002 and was already approved to run in 2021. It uses unique beams of naturally polarized muons and unpolarized hadrons of 160, 190 or 200 GeV impinging on polarized and unpolarized proton, isoscalar or heavy targets to study fundamental aspects of QCD, as the structure of nucleons, hadron spectroscopy and the pion polarizability. The collected data allow measurements on the spin structure of nucleons, not only in the collinear approximation but also on nucleon tomography, either via deeply virtual Compton scattering (DVCS) and deeply virtual meson production (DVMP) which give access to generalized parton distributions (GPDs), or via semi-inclusive deep inelastic scattering (SIDIS) and polarized Drell-Yan (DY) which give access to transverse-momentum dependent parton distribution functions (TMDs). Moreover, hadron multiplicities extracted from semi-inclusive deep inelastic scattering data can be used as input for the computation of fragmentation functions (FFs) in QCD fits. A selection of the latest published and preliminary results of COMPASS in the scope of the study of the structure of nucleons and the hadronization of quarks will be presented.
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Condensed Matter Physics and Materials Science - The Myron Strongin Seminar
"Disappearance of Superconductivity Due to Vanishing Coupling in the Overdoped High-Temperature Cuprate Superconductors"
Presented by Tonica Valla, BNL
Monday, April 15, 2019, 1:30 pm
ISB Bldg. 734, Conf. Rm. 201 (upstairs)Hosted by: Weiguo Yin and Jing Tao
In high-temperature cuprate superconductors, superconductivity is accompanied by a "plethora of orders", and phenomena that may compete, or cooperate with superconductivity, but which certainly complicate our understanding of origins of superconductivity in these materials. While prominent in the underdoped regime, these orders are known to significantly weaken or completely vanish with overdoping. Here, we approach the superconducting phase from the more conventional highly overdoped side. We present angle-resolved photoemission spectroscopy (ARPES) studies of Bi2Sr2CaCu2O8+d (Bi2212) single crystals cleaved and annealed in ozone to increase the doping all the way to the metallic, non-superconducting phase. We show that the mass renormalization in the antinodal region of the Fermi surface, associated with the structure in the quasiparticle self-energy, that possibly reflects the pairing interaction, monotonically weakens with increasing doping and completely disappears precisely where superconductivity disappears. This is the direct evidence that in the overdoped regime, superconductivity is determined by the coupling strength. A strong doping dependence and an abrupt disappearance above the transition temperature (Tc) eliminate the conventional phononic mechanism of the observed mass renormalization and identify the onset of spin-fluctuations as its likely origin.
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Physics Colloquium
"Future Circular Collider"
Presented by Michael Benedikt, CERN
Friday, April 12, 2019, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: George Redlinger & Maria Chamizo Llatas
The global Future Circular Collider Study, launched in 2014 by CERN as host institute, has published its conceptual design report by the end of 2018, as input to the update of the European Strategy for Particle Physics. Today, a staged Future Circular Collider (FCC), consisting of a luminosity-frontier highest-energy electron-positron collider (FCC-ee) followed by an energy-frontier hadron collider (FCC-hh), promises the most far-reaching physics program for the post-LHC era. FCC-ee is a precision instrument to study the Z, W, Higgs and top particles, and o?ers unprecedented sensitivity to signs of new physics. Most of the FCC-ee infrastructure can later be reused for the subsequent hadron collider, FCC-hh. The FCC-hh provides proton-proton collisions at a centre-of-mass energy of 100 TeV and can directly produce new particles with masses of up to several tens of TeV. This collider will also measure the Higgs self-coupling and explore the dynamics of electroweak symmetry breaking. Heavy-ion collisions and ep collisions (FCC-eh) further contribute to the breadth of the overall FCC program. The integrated FCC infrastructure will serve the particle physics community through the end of the 21st century. This presentation will summarize the conceptual designs of FCC-ee and FCC-hh, covering the machine concepts, the R&D for key technologies, infrastructure planning, initial considerations for the experiments, and a possible implementation schedule.
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NT / RIKEN Seminar
"A Complex Path Around the Sign Problem"
Presented by Paolo Bedaque, U Maryland
Friday, April 12, 2019, 2 pm
Building 510, CFNS Seminar Room 2-38Hosted by: Niklas Mueller
The famous "sign problem" is the main roadblock in the path to a Monte Carlo solution of QCD at finite densities and the study of real time dynamics. We review a recent developed approach to this problem based on deforming the domain of integration of the oath integral into complex field space. After discussing the math involved in the complex analysis of multidimensional spaces we will talk about the advantages/disadvantages of using Lefschetz thimbles, "learnifolds" and "optimized manifolds" as the alternative integration manifold as well as the algorithms that go with them. Several examples of lower dimensional field theories will be presented.
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Particle Physics Seminar
"Neutrino Interaction Modeling and Tuning"
Presented by Libo Jiang, University of Pittsburgh
Thursday, April 11, 2019, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Mary Bishai
GENIE is a well-knows event generator provides the simulation of neutrino interactions, and performs a highly-developed global analysis of neutrino scattering. It handles all neutrinos and targets, and all processes relevant from MeV to PeV energy scales. I am going to present the modelling of neutrino interactions and results of tuning against experimental data.
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Condensed-Matter Physics & Materials Science Seminar
"Tailoring electronic and thermal properties of bulk Cu26T2(Ge,Sn)6S32 colusite through defects engineering and functionalization of the conductive network"
Presented by Emmanuel Guilmeau, CRISMAT Laboratory, Caen, France
Thursday, April 11, 2019, 1:30 pm
Bldg. 734, ISB Conference Room 201 (upstairs)Hosted by: Qiang Li
A complete study of the structure and thermoelectric properties of colusite Cu26T2(Ge,Sn)6S32 (T = V, Cr, Mo, W) is presented. A brief introduction provides a state-of-theart/survey of thermoelectric sulfides, with a special focus on the structural features and transport properties relationship in Cu-based sulfides. In the first part of this presentation, we highlight the key role of the densification process on the formation of short-to-medium range structural defects in Cu26V2Sn6S32 [1]. A simple and powerful way to adjust carrier concentration combined with enhanced phonon scattering through point defects and disordered regions is described. By combining experiments with band structure and phonons calculations, we elucidate, for the first time, the underlying mechanisms at the origin of the intrinsically low thermal conductivity in colusite samples as well as the effect of S vacancies and antisite defects on the carrier concentration. In the second part, we demonstrate the spectacular role of the substitution of V5+ by hexavalent T6+ cations (Cr, Mo and W) on the electronic properties, leading to high power factors [2]. In particular, Cu26Cr2Ge6S32 shows a value of 1.53 mW m-1 K-2 at RT that reaches a maximum value of 1.94 mW m-1 K-2 at 700 K. The rationale is based on the concept of conductive "Cu-S" network, which in colusites corresponds to the more symmetric parent sphalerite structure. The interactions within the mixed octahedral-tetrahedral [TS4]Cu6 complexes are shown to be responsible for the outstanding electronic transport properties. [1] C. Bourgès et al., J. Amer. Chem. Soc. 140 (2018) 2186 [2] V. Pavan Kumar et al., Adv. Energy Mater. 9 (2019) 1803249
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Environmental & Climate Sciences Department Seminar
"Simulating Mixed-Phase Clouds at High Latitudes: Model Evaluation, Improvement, and Interactions with Aerosol"
Presented by Xiahong Liu, Univ. Wyoming
Thursday, April 11, 2019, 11 am
Large Conference Room, Bldg. 490Hosted by: Damao Zhang
Mixed-phase clouds are frequently observed in the Arctic and Antarctic and over the Southern Ocean, and have important impacts on the surface energy budget and regional climate. Global climate models (GCMs), an important tool for studying the climate change still have large biases in simulating the mixed-phase cloud properties, including supercooled liquid amount and liquid and ice phase partitioning. In this talk, I will present our recent works on mixed-phase clouds: (1) improving the representations of subgrid mixing and partitioning between cloud liquid and ice in mixed-phase clouds in the DOE's Energy Exascale Earth System Model (E3SM). Model simulations are evaluated against observation data obtained in the DOE Atmospheric Radiation Measurement (ARM) Program's field campaigns and long-term ground-based multi-sensor measurements; and (2) investigating the effects of aerosols, including dust and sea spray aerosol, on mixed-phase clouds. We found that dust, as ice nucleating particles (INPs), induces a global net warming via its indirect effect on mixed-phase clouds with a predominant warming in the NH midlatitudes and a cooling in the Arctic. INP sources of sea spray aerosol vary with time and geographic location with the maximum contribution in the marine boundary layer over the Southern Ocean, where dust has a limited influence. Modeled INP concentrations are compared with observations from different campaigns (e.g., MARCUS, SOCRATES, CAPRICORN).
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Condensed-Matter Physics & Materials Science Seminar
"Importance of electron interactions in understanding the photo-electron spectroscopy and the Weyl character of MoTe2"
Presented by Niraj Aryal, Florida State University
Thursday, April 11, 2019, 11 am
ISB Bldg. 734 Conference Room 201 (upstairs)Hosted by: Weiguo Yin
Weyl semimetals are crystalline materials that host pairs of chiral Weyl Fermions (WFs) as low energy excitations. Such WFs act as sources and sinks of Berry curvature and can contribute to many exotic transport properties. Recently, inversion symmetry broken transition metal dichalcogenide materials like MoTe2 and WTe2 have been predicted to host type-II WFs by DFT calculations and ARPES experiments. However, quantum oscillation experiments (QOE) disagree with the DFT calculations thus raising doubt about the existence of Weyl physics in these materials [1]. In order to address this discrepancy, we studied the role of electron interactions in Td-MoTe2 by employing DFT where the onsite Coulomb repulsion (Hubbard U) for the Mo 4d states is included within the DFT+U scheme. We found that in addition to explaining the QOE, inclusion of electron interaction is needed to explain the light-polarization dependence measured by ARPES [2]. We also found that while the number of Weyl points (WPs) and their position in the Brillouin Zone change as a function of U, a pair of such WPs very close to the Fermi level survive the inclusion of these important corrections. Our calculations suggest that the Fermi surface of Td-MoTe2 is in the vicinity of a correlations-induced Lifshitz transition which can be probed experimentally. If time allows, I will also present briefly our study of the interface between topological insulator and non-topological materials which are important for band engineering and studying emergent fundamental phenomena. References [1] D. Rhodes, R. Schonemann, N. Aryal, Q.R. Zhou et al., Bulk Fermi surface of the Weyl type-II semimetallic candidate ?-MoTe2, Phys. Rev. B 96, 165134 (2017). [2] N. Aryal and E. Manousakis, Importance of electron correlations in understanding the photo-electron spectroscopy and the Weyl character of MoTe2, Phys. Rev. B 99, 035123 (2019).
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Particle Physics Seminar
"The Search for the dark vector boson"
Presented by Diallo Boye, BNL
Wednesday, April 10, 2019, 4 pm
Small Seminar Room, Bldg. 510Hosted by: Alessandro Tricolli
Hidden sector or dark sector states appear in many extensions to the Standard Model, to provide a particle candidate for dark matter in universe or to explain astrophysical observations such the as positron excess observed in the cosmic radiation flux. A hidden or dark sector can be introduced with an additional U(1)d dark gauge symmetry. The discovery of the Higgs boson during Run 1 of the Large Hadron Collider opens a new and rich experimental program based on the Higgs Portal. This discovery route uses couplings to the dark sector at the Higgs level, which were not experimentally accessible before. These searches use the possible exotic decays: H -> Z Zd -> 4l and H -> Zd Zd -> 4l. Here Zd is a dark vector boson. We have experience of this search from the Run 1 period of the LHC using the ATLAS detector at CERN. These results showed (tantalizingly) two signal events where none were expected, so that in the strict criteria of High Energy Physics, the result was not yet statistically significant. The Run 1 analysis for 8 TeV collision energy is further developed in Run 2 with 13 TeV collision energy, to expand the search area, take advantage of higher statistics, a higher Higgs production cross section, and substantially better performance of the ATLAS detector. The analysis is extended to search for heavier scalars decaying to dark vector bosons.
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CFN Special Colloquium
"Discovering novel materials, and novel physics, with first-principles"
Presented by Nicola Marzari, École Polytechnique Fédérale de Lausanne (EPFL)
Wednesday, April 10, 2019, 3:30 pm
CFN, Bldg 735, 2nd Floor Seminar RoomHosted by: Mark Hybertsen
First-principles simulations are one of the greatest accelerators in the world of science and technology. To provide some context, one could mention that 30,000 papers on density-functional theory are published every year; that 12 of these are in the top-100 most-cited papers in the entire history of science, engineering, and medicine; or that the doubling in capacity every 14 months has been the underwriter of computational science for the past 30 years. I'll highlight some of my own scientific, structural, and policy perspectives on this, taking as a case study the discovery of novel two-dimensional materials and of their properties and applications. I'll then argue how the need to calculate materials properties often forces a critical evaluation of some stalwarts of condensed-matter physics: in this case, learning that phonons are just a high-temperature approximation for heat carriers, or discovering that the Boltzmann transport equation can be generalized to describe simultaneously the propagation and interference of phonon wavepackets, thus unifying the description of thermal transport in crystals and glasses. Bio: Nicola Marzari holds the chair of Theory and Simulation of Materials at the École Polytechnique Fédérale de Lausanne, where he is also the director of the Swiss National Centre for Competence in Research MARVEL, on Computational Design and Discovery of Novel Materials (2014-26). Previous tenured appointment include the Toyota Chair for Materials Engineering at the Massachusetts Institute of Technology and the first Statutory (University) Chair of Materials Modelling at the University of Oxford, where he was also the director of the Materials Modelling Laboratory. He is the current chairman of the Psi-k Charity and Board of Trustees, and holder of an Excellence Chair at the University of Bremen.
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BWIS Sponsored Event
"How Beauty Leads Physics Astray"
Presented by Sabine Hossenfelder, Frankfurt Institute for Advanced Studies, Germany
Tuesday, April 9, 2019, 5 pm
Large Seminar Room, Bldg. 510Hosted by: Vivian Stojanoff
To develop fundamentally new laws of nature, theoretical physicists often rely on arguments from beauty. Simplicity and naturalness in particular have been strongly influential guides in the foundations of physics ever since the development of the standard model of particle physics. In this lecture I argue that arguments from beauty have led the field into a dead end and discuss what can be done about it.
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Physics Colloquium
"Do Women Get Fewer Citations Than Men?"
Presented by Sabine Hossenfelder, Frankfurt Institute for Advanced Studies, Germany
Tuesday, April 9, 2019, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Berndt Mueller
I will talk about the results of a citation analysis on publication data from the arXiv and inspire in which we explored gender differences. I will further explain how we can use bibliometric analysis to improve the efficiency of knowledge discovery.
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Condensed-Matter Physics & Materials Science Seminar
""Charge and lattice entanglement in quantum materials observed by TEM: Tb2Cu0.83Pd0.17O4 and Cu2S""
Presented by Wei Wang, Institute of Physics, Chinese Academy of Sciences, Beijing
Tuesday, April 9, 2019, 3 pm
Bldg. 480, Conference RoomHosted by: Jing Tao
Plenty of physical properties in strongly electron correlated system are thought to arise from intricate interplay among charge, spin, orbital and lattice. Understanding the structural origin of these functionalities, such as superconductivity, multiferroics, etc, has attracted tremendous attention for decades. Using electron diffraction technique in TEM, we recently studied the modulated structure in Tb2Cu0.83Pd0.17O4 compound and phase transition in Cu2S. After a brief introduction of TEM techniques that I have employed for the study, I will report observations of electron-beam-induced smectic-nematic phase transitions in Tb2Cu0.83Pd0.17O4. Electron diffraction and HAADF-STEM images indicate a superlattice structure with Cu/Pd displacements perpendicular to the Cu-O plane on Cu sites. In addition, the superlattice modulation undergoes a reversible smectic-nematic phase transition under the electron beam illumination. Our in situ TEM results imply that the modulated structure root in a charge ordering at Cu sites. Then I will switch to an on-going study of the Cu2S at high temperature. Previous reports show that the crystal structural of Cu2S can be manipulated by electron beam illumination, suggesting a strong coupling between charge and lattice. To explore the structural phase transition and to have a better understanding of superionic behavior in this material, we focus on diffuse scattering in the electron diffraction patterns obtained at high temperatures, which results from short range ordering of Cu atoms. Electron diffraction tomographyic data were collected in order to reconstruct the real-space structure for Cu atoms. Preliminary results will be shown followed by a discussion with early-stage interpretations.
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High Energy Theory Seminar
"Dark Matter — or What?"
Presented by Sabine Hossenfelder, Frankfurt Institute for Advanced Studies, Germany
Tuesday, April 9, 2019, 11 am
Small Seminar Room, Bldg. 510Hosted by: Berndt Mueller
In this talk I will explain (a) what observations speak for the hypothesis of dark matter, (b) what observations speak for the hypothesis of modified gravity, and (c) why it is a mistake to insist that either hypothesis on its own must explain all the available data. The right explanation, I will argue, is instead a suitable combination of dark matter and modified gravity, which can be realized by the idea that dark matter has a super fluid phase.
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NT / RIKEN seminar
"The Color Glass Condensate density matrix: Lindblad evolution, entanglement entropy and Wigner functional"
Presented by Alex Kovner, U Connecticut
Friday, April 5, 2019, 2 pm
Building 510, CFNS Seminar Room 2-38Hosted by: Niklas Mueller
We introduce the notion of the Color Glass Condensate (CGC) density matrix ρ̂ . This generalizes the concept of probability density for the distribution of the color charges in the hadronic wave function and is consistent with understanding the CGC as an effective theory after integration of part of the hadronic degrees of freedom. We derive the evolution equations for the density matrix and show that it has the celebrated Kossakowsky-Lindblad form describing the non-unitary evolution of the density matrix of an open system. Additionally, we consider the dilute limit and demonstrate that, at large rapidity, the entanglement entropy of the density matrix grows linearly with rapidity according to dSe/dy=γ, where γ is the leading BFKL eigenvalue. We also discuss the evolution of ρ̂ in the saturated regime and relate it to the Levin-Tuchin law and find that the entropy again grows linearly with rapidity, but at a slower rate. Finally we introduce the Wigner functional derived from this density matrix and discuss how it can be used to determine the distribution of color currents, which may be instrumental in understanding dynamical features of QCD at high energy.
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Physics Colloquium
"Views and news on chiral transport"
Presented by Karl Landsteiner
Thursday, April 4, 2019, 4 pm
Large Seminar Room, Bldg. 510Hosted by: Niklas Mueller
I present an effective action approach to chiral transport. Chiral Magnetic and Chiral Vortical Effect are treated in exact parallel and result in the known dependence on chemical potential and temperature. The approach sheds light on some of the more obscure features of chiral transport such as covariant and consistent anomalies and a seeming mismatch of the derivative expansion. As a related application I will comment on the thermal Hall effect on 2D topological insulators. Then I discuss a new example of chiral transport: anomalous Hall viscosity at the quantum critical point of the Weyl-semimetal/insulator transition. Results from a holographic model will be compared to a weak coupling quantum field theory analysis.
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Particle Physics Seminar
"Flavour physics with dynamical chiral fermions"
Presented by Peter Boyle, University of Edinburgh
Thursday, April 4, 2019, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Hooman Davoudiasl
I discuss recent simulations with dynamical chiral fermions. In particular I focus on neutral kaon mixing amplitudes in and beyond the standard model, calculated for the first time with physical quark masses. A puzzle in the non-perturbative renormalisation of the BSM operators is resolved. The prospects for extension of this calculation to B-meson mixing amplitudes is discussed, and initial results for the standard model B mixing amplitudes presented. Prospects for future calculations over the next five years are considered.
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Physics Colloquium
"Prospects on nucleon tomography"
Presented by Herve Moutard, Université Paris-Saclay
Wednesday, April 3, 2019, 3 pm
Large Seminar Room, Bldg. 510Hosted by: Salvatore Fazio
Much attention has been devoted in recent years to the three-dimensional quark and gluon structure of the nucleon. In particular the concept of Generalized Parton Distributions promises an understanding of the generation of the charge, spin, and energy-momentum structure of the nucleon by its fundamental constituents. Forthcoming measurements with unprecedented accuracy at Jefferson Lab and at a future electron-ion collider will presumably challenge our quantitative description of the three-dimensional structure of hadrons. To fully exploit these future experimental data, new tools and models are currently being developed. After a brief reminder of what make Generalized Parton Distributions a unique tool to understand the nucleon structure, we will discuss the constraints provided by the existing measurements and review recent theoretical developments. We will explain why these developments naturally fit in a versatile software framework, named PARTONS, dedicated to the phenomenology and theory of GPDs.
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Condensed-Matter Physics & Materials Science Seminar
"Topological semimetals predicted from first-principles and theoretical approaches"
Presented by Jiawei Ruan, School of Physics, Nanjing University, China
Monday, April 1, 2019, 11 am
Building 734, Seminar Room 201Hosted by: Weiguo Yin
Weyl semimetals are new states of matter which feature novel Fermi arcs and exotic transport phenomena. Based on first-principles calculations, we report that the HgTe-class materials [1] as well as four chalcopyrites [2] are ideal Weyl semimetals, having largely separated Weyl points and uncovered Fermi arcs that are amenable to experimental detections. We also construct a minimal effective model to capture the low-energy physics of this class of Weyl semimetals. Our discovery is a major step toward a perfect playground of intriguing Weyl semimetals and potential applications for low-power and high-speed electronics. Besides the ideal Weyl semimetals, I will talk about Non-Hermitian nodal-line semimetals with an anomalous bulk-boundary correspondence [3]. I will also present recent results of saddle surface in topological materials and a new method to construct a simplified tight-binding model based on group theory analysis. [1] JR et al., Nature communications 7, 11136 (2016). [2] JR et al., PRL 116, 226801 (2016). [3] H. Wang, JR, and H. Zhang, PRB 99, 075130 (2019).
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NT/RIKEN Seminar
"Toward a unified description of both low and high ptparticle production in high energy collisions"
Presented by Jamal Jalilian-Marian, Baruch College, City University of New York
Friday, March 29, 2019, 2 pm
Building 510, CFNS Seminar Room 2-38Hosted by: Niklas Mueller
Inclusive particle production at high p_t is successfully described by perturbative QCD using collinear factorization formalism with DGLAP evolution of the parton distribution functions. This formalism breaks down at small Bjorken x (high energy) due to high gluon density (gluon saturation) effects. The Color Glass Condensate (CGC) formalism is an effective action approach to particle production at small Bjorken x (low p_t) which includes gluon saturation. The CGC formalism nevertheless breaks down at intermediate/large Bjorken x, corresponding to the high p_t kinematic region in high energy collisions. Here we describe the first steps taken towards the derivation of a new formalism, with the ultimate goal of having a unified formalism for particle production at both low and high p_t in high energy hadronic/heavy ion collisions.
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Physics Colloquium
"Quantum Information Science Landscape, Vision, and NIST"
Presented by Carl Williams, NIST
Tuesday, March 26, 2019, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Andrei Nomerotski
The first part of the colloquium will provide an overview of United States government's interest in quantum information science from the National Strategic Overview for Quantum Information Science that established the policy objectives for this administration to the National Quantum Initiative Act that formalizes parts of this strategy for key civilian science agencies. This portion of the talk will conclude with placing the United States strategy in the global context and describe how the United States plans to establish the foundation for the quantum 2.0 economy. The second part of the colloquium will begin with a high-level overview of NIST, of NIST's interest in Quantum Information Science, before talking briefly about some interesting highlights from NIST laboratories. Moving from the highlights, the talk will explore ongoing and future metrological applications followed by some hypothetical conjectures of future technological applications with a focus on how quantum information science and its technology may impact fundamental physics from exploring potential time variation of fundamental constants to future probes of dark matter and gravitational waves.
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Particle Physics Seminar
"Deep learning at the edge of discovery at the LHC"
Presented by Javier Duarte, FNAL
Monday, March 25, 2019, 2:30 pm
Small Seminar Room, Bldg. 510Hosted by: Alessandro Tricoli
The discovery of the Higgs boson at the Large Hadron Collider in 2012 opened a new sector for exploration in the standard model of particle physics. Recent developments, including the use of deep learning to identify a complex but common decay of the Higgs boson to bottom quarks, have expanded our ability to study the production of Higgs bosons with very large momenta. By studying these Higgs bosons and measuring their momentum spectrum, we may be able to discover new physics at very high energy scales inaccessible directly at the LHC. I will explain these searches and the direction that deep learning is taking in particle physics, especially how it's changing the way we think about the trigger, event reconstruction, and our computing paradigm.
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Particle Physics Seminar
"Installation and preliminary results from ProtoDUNE Single Phase experiment at CERN"
Presented by Maura Spanu, BNL
Thursday, March 21, 2019, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Chao Zhang
DUNE is a leading-edge, international experiment for neutrino science and proton decay. Its ambitious physics program requires a careful prototyping of the engineering solutions envisaged for the scale-up of the LArTPC technology, as well as a careful control of the systematics through the acquisition of a deep knowledge of the detector response and performances. ProtoDUNE is an extensive prototype program (ProtoDUNE) development at the European Research Center (CERN) Neutrino Platform facility with the aim to answer to all the open questions about DUNE design. The Single Phase prototype (ProtoDUNE SP) has been assembled in the EHN1 extension at CERN between 2016 and 2018 and it successfully took its first beam data from a dedicated SPS tertiary line from September to November 2018.
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Physics Colloquium
"Development of LArTPC for Neutrino Physics"
Presented by Xin Qian, BNL
Tuesday, March 19, 2019, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Andrei Nomerotski
Liquid Argon Time Projection Chamber (LArTPC), with its mm-scale position resolution and the full-active-volume imaging-aided calorimetry, is an excellent device to detect accelerator neutrinos at GeV energy range. This technology may hold the key to search for new CP violation in the lepton sector, to determine the neutrino mass hierarchy, to search for baryon number violation, and to search for sterile neutrino(s). In this talk, I will review the existing achievements and current status of the detector development.
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Nuclear Physics Seminar
"Modified Structure of Protons and Neutrons in Correlated Pairs"
Presented by Dr. Barak Schmookler, Center for Frontiers in Nuclear Science, Stony Brook University
Tuesday, March 19, 2019, 11 am
Small Seminar Room, Bldg. 510Hosted by: Jin Huang
It has been known for several decades that the inelastic structure of the nucleon is modified by the presence of the nuclear medium. This modification is called the EMC effect. However, there is still no consensus as to the underlying QCD-based quark-gluon dynamics driving the effect. One approach to describe the EMC effect is to slightly modify the structure of all the nucleons in the nucleus. Recent evidence, however, suggests that the EMC effect may arise due to two-nucleon Short Range Correlations (SRC), which are pairs of nucleons close together in the nucleus. If this is true, it implies that nucleons are largely unmodified most of the time, but have their structure significantly modified when they temporarily fluctuate into SRC pairs. In this presentation, I will discuss the experimental evidence linking the EMC effect to two-nucleon SRCs. I will then describe a new data-driven phenomenological model of the EMC effect based on neutron-proton SRC pairs, and I will show that this model can consistently describe the effect across nuclei.
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NT/RIKEN Seminar
"Baryons as Quantum Hall Droplets"
Presented by Zohar Komargodski, Simons Center, Stony Brook
Friday, March 15, 2019, 2 pm
Building 510, CFNS Room 2-38Hosted by: Niklas Mueller
We revisit the problem of baryons in the large N limit of Quantum Chromodynamics. A special case in which the theory of Skyrmions is inapplicable is one-flavor QCD, where there are no light pions to construct the baryon from. More generally, the description of baryons made out of predominantly one flavor within the Skyrmion model is unsatisfactory. We propose a model for such baryons, where the baryons are interpreted as quantum Hall droplets. An important element in our construction is an extended, 2+1 dimensional, meta-stable configuration of the η′ particle. Baryon number is identified with a magnetic symmetry on the 2+1 dimensional sheet. If the sheet has a boundary, there are finite energy chiral excitations which carry baryon number. These chiral excitations are analogous to the electron in the fractional quantum Hall effect. Studying the chiral vertex operators we are able to determine the spin, isospin, and certain excitations of the droplet. In addition, balancing the tension of the droplet against the energy stored at the boundary we estimate the size and mass of the baryons. The mass, size, spin, isospin, and excitations that we find agree with phenomenological expectations.
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Condensed-Matter Physics & Materials Science Seminar
"Neutron scattering study of strongly correlated systems"
Presented by Yao Shen, Fudan University, China
Monday, March 11, 2019, 1:30 pm
ISB Bldg. 734, Conf. Rm. 201 (upstairs)Hosted by: Mark Dean
In strongly correlated systems, interactions between various microscopic degrees of freedom with similar energy scales can induce strong competition and frustration, leading to exotic phenomena. Here we use neutron scattering technique to study several strongly correlated systems to show how the competition and interplay between these degrees of freedom can induce different phases and properties. 1) In the pressure-induced superconductor CrAs, the competition between various magnetic interactions lead to a noncollinear helimagnetic order. In addition, CrAs exhibits a spin reorientation at a critical pressure (Pc ~ 0.6 GPa), which is accompanied by a lattice anomaly and coincides with the emergence of bulk superconductivity, indicating the strong interplay between magnetic, structural and electronic degrees of freedom. 2) FeSe, the structurally simplest iron-based superconductor, shows nematic order at 90 K, but no magnetic order in the parent phase. Our neutron scattering experiments reveal both stripe and Neel spin fluctuations that are coupled to the nematicity. The competition between these two phases suppress the magnetic order and drive the system into a nematic quantum disordered paramagnet. Similar phenomenon is observed in YFe2Ge2, in which the magnetic order is suppressed by the competition between stripe type AFM phase and in-plane FM phase. 3) In the heavily electron-doped FeSe based superconductor Li0.8Fe0.2ODFeSe (Tc=41 K), a twisted dispersion of spin excitations is observed which may be caused by the competition between itinerant and local electrons, analogous to the hole-doped cuprates which host remarkably high Tc as well. 4) In the two-dimensional triangular lattice antiferromagnet YbMgGaO4, due to the strong spin-orbit coupling and crystalline electric field (CEF), the low-lying crystal field ground state is a Kramers doublet. The geometric frustration is enhanced by the anisotropic interactions and a quantum sp
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Particle Physics Seminar
"The PROSPECT Antineutrino Detector and Early Physics Results"
Presented by Xianyi Zhang, Illinois Institute of Technology
Thursday, March 7, 2019, 1:30 pm
Small Seminar Room, Bldg. 510Hosted by: Elizabeth Worcester
PROSPECT, Precision Reactor Oscillation and SPECTrum, is a short baseline reactor antineutrino experiment. The PROSPECT antineutrino detector is an optically segmented liquid scintillator detector deployed ~7 m from a highly enriched U-235 reactor. This detector was designed to investigate discrepancies in the reactor antineutrino flux and spectrum by model-independently probing the eV-scale sterile neutrino oscillation from nuclear fission reactor, as well as precisely measuring the U-235 antineutrino spectrum. The particle multi-segment scattering in PROSPECT detector brought a typical challenge in characterizing the scintillator nonlinearity. This talk details the energy scale study for PROSPECT with data-MC comparison of detector calibrations. The detector construction, commissioning, and its early physics measurements are also presented.
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Particle Physics Seminar
"Neutrino cross sections"
Presented by Callum Wilkinson, University of Bern
Tuesday, March 5, 2019, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Elizabeth Worcester
Current and planned neutrino oscillation experiments operate in the 0.1-10 GeV energy regime and use a variety of nuclear targets. At these energies, the neutrino cross section is not well understood: a variety of interaction processes are possible and nuclear effects play a significant role. This talk will give an overview of the state of neutrino cross sections, and explore their relationship with neutrino oscillation experiments.
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Particle Physics Seminar
"Measurement of LAr purity using Cosmic Muons"
Presented by Monica Nunes, IFGW/UNICAMP, Brazil
Monday, March 4, 2019, 3 pm
3-209B, Bldg. 510Hosted by: Mary Bishai
LArIAT is an experiment based on a LArTPC aiming to study relevant cross sections of charged particles with argon as well as the development of the related instrumentation. Charged particle crossing the detector excite and ionize the argon atoms and the electrons generated by the ionization are drifted in an electric field towards the anodic wire planes of the TPC. With electronegative impurities in the liquid argon, the amount of charge collected by the wires is going to be smaller and affect the quality of the results obtained in the experiment. Cosmic muons that cross the TPC between beam spills is a valuable tool for measuring the liquid argon purity inside the detector. With the electron lifetime obtained with the purity analysis based on cosmics, is possible to correct data used for all other studies based on charge collection of the LArTPC. In this seminar, I'll present the method and the results obtained in the LArIAT experiment. I'll also present other tasks that I performed on LArIAT during my PhD research.
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Particle Physics Seminar
"Status and physics potential of the JUNO experiment"
Presented by Zeyuan Yu, Institute of High Energy Physics, China
Thursday, February 28, 2019, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Chao Zhang
The Jiangmen Underground Neutrino Observatory (JUNO) is a 20 kton multi-purpose liquid scintillator detector with an unprecedented energy resolution of 3% at 1 MeV being built in a dedicated underground laboratory in China and expected to start data taking in 2021. The main physics goal of the experiment is the determination of the neutrino mass ordering with a significance of 3-4 sigma within six years of running using electron anti-neutrinos coming from two nuclear power plants at a baseline of about 53 km. Beyond this fundamental question, JUNO will also have a very rich physics program including the precise measurement at a sub-percent level of the solar neutrino oscillation parameters, the detection of low-energy neutrinos coming from galactic core-collapse supernova, diffuse supernova background, the Sun, the Earth (geo-neutrinos) but also proton decay searches. This talk will give an overview on the JUNO physics potential and the current status of the project.
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HET Seminar
"Probing New Physics with Neutrino Scattering"
Presented by Ian Shoemaker, Virginia Tech
Wednesday, February 27, 2019, 2:30 pm
Small Seminar Room, Bldg. 510Hosted by: Gopolang Mohlabeng
Current experimental sensitivities allow for neutrino scattering to be probed over a range of energy scales. In this talk, I'll discuss phenomenological probes of new physics using neutrino scattering at zero, GeV, and EeV momentum transfer. At zero momentum transfer, the forward coherent scattering of neutrinos on background particles provides novel sensitivity to Dark Matter. At MeV-GeV energies, the solar/atmospheric fluxes allow for the production of heavy sterile neutrinos at IceCube and direct detection experiments, resulting in distinctive signatures. Lastly, I'll discuss sterile neutrino scattering in the Earth as a possible explanation of the anomalous EeV events reported by ANITA.
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Physics Colloquium
"Precision measurement of neutrinos at Hyper-Kamiokande"
Presented by Akira Konaka, TRIUMF
Tuesday, February 26, 2019, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: George Redlinger
Hyper-Kamiokande (HyperK) is a water Cherenkov neutrino detector whose construction in Japan was recently approved. The fiducial mass is 187kton, eight times larger than the Super-Kamiokande detector. The upgraded J-PARC accelerator located 295km away will provide high intensity neutrino and anti-neutrino beams tuned at the oscillation maximum. In this talk, I will describe the challenges of the systematic uncertainties in future neutrino oscillation experiments and how HyperK plans to address them. In addition to the observation of CP violation, Hyper-Kamiokande will explore directions that may become the main research topic in the future if something new is discovered: Precision neutrino oscillations to test the unitarity of the lepton flavour mixing, neutrino astronomy, such as supernova neutrinos and searches for astrophysical point sources of neutrinos, and searches for phenomena beyond the standard model, such as dark matter and nucleon decays.
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Condensed-Matter Physics & Materials Science Seminar
"Unconventional superconductivity and complex tensor order in half-Heusler superconductors"
Presented by Igor Boettcher, University of Maryland
Tuesday, February 26, 2019, 1:30 pm
ISB Bldg. 734, Conf. Rm. 201 (upstairs)Hosted by: Laura Classen
A revolutionary new direction in the field of superconductivity emerged recently with the synthesis of superconductors with strong inherent spin-orbit coupling such as the half-Heusler alloys. Due to band inversion, the low-energy degrees of freedom are electrons at a three-dimensional quadratic band touching point with an effective spin 3/2, which allows for higher-spin Cooper pairing and potentially topological superconductivity. I will illuminate some possibilities for unconventional superconductivity in this system, in particular a novel superconducting quantum critical point and the transition into a phase with complex tensor order, which is a superconducting state captured by a complex second-rank tensor valued order parameter describing Cooper pairs having spin 2. Here the interplay of both tensorial and complex nature results in a rich and intriguing phenomenology. I will highlight how optical response measurements can shed light on the phase structure of individual compounds.
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NT / RIKEN Seminar
"Quantum Chaos, Wormholes and the Sachdev-Ye-Kitaev Model"
Presented by Jacobus Verbaarschot, Stony Brook University
Friday, February 22, 2019, 2 pm
2-38 CFNS Seminar RoomHosted by: Niklas Mueller
The Sachdev-Ye-Kitaev (SYK) model has a long history in nuclear physics where its precursor was introduced as a model for the two-body nuclear interaction to describe the spectra of complex nuclei. Most notably, its level density is given by the Bethe formula and its level correlations are consistent with chaotic motion of the nucleons. Recently, this model received a great of attention as a solvable model for the quantum states of a black hole, exactly because of these properties. In this lecture we introduce the SYK model from a nuclear physics perspective and discuss its chaotic nature and its relation with black hole physics. We end with a summary of recent work on two SYK models coupled by a spin-spin interaction as a model for wormholes.
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Particle Physics Seminar
"Probing New Physics and the Nature of the Higgs Boson at ATLAS"
Presented by Lailin Xu, University of Michigan
Thursday, February 21, 2019, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Alessandro Tricoli
The long-sought Higgs boson discovered at the LHC completes the Standard Model of the particle physics. During the last six years, substantial achievements have been made to probe the nature of the Higgs boson. Participle physics is however at an impasse: deep mysteries of the Electroweak symmetry breaking remain unanswered, and long-awaited new physics phenomena beyond the SM have not shown up yet. In this talk, I start with a brief overview on the current profile of measurements of the Higgs boson properties and couplings. I then present Higgs measurements in the four-lepton channel, and how we use the Higgs boson as a portal in the quest for new physics. In the end, I discuss the prospect of the Higgs measurements including the Higgs self-coupling at future colliders.
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Physics Colloquium
"Physics education research in higher education: What can we learn from the top cited papers in the Physical Review?"
Presented by Charles Henderson, Western Michigan University
Tuesday, February 19, 2019, 3:30 pm
Large Seminar Room, Bldg. 510The journal Physical Review Physics Education Research was started in 2005 as the archival research journal for the field of Physics Education Research (PER). In this talk I will identify some important findings from the field of PER based on highly cited articles from the journal. For example, there is strong evidence that in typical physics courses many students do not learn the core concepts of the discipline; student beliefs about physics become less expert like; and there is a significant gender gap, with men outperforming women. Many PER-based instructional strategies can improve student knowledge and some instructional strategies can improve student beliefs. However, implementation of these strategies is low because the field often uses ineffective dissemination strategies.
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Condensed-Matter Physics & Materials Science Seminar
": Electronic structure of d-metal systems as revealed by ab initio modeling of resonant inelastic X-ray scattering"
Presented by Lei Xu, Leibniz Institute for Solid State and Materials Research Dresden, Germany
Friday, February 15, 2019, 11 am
ISB Bldg. 734 Conference Room 201 (upstairs)Hosted by: Weiguo Yin
I will present our work on the theoretical investigation of the electronic structure, magnetic interactions and resonant inelastic X-ray scattering (RIXS) in 3d or 4d-5d transition metal (TM) compounds by using wave-function-based many-body quantum chemistry (QC) methods. My presentation contains two parts. In the first part, I will discuss the magnetic properties of 4d and 5d TM ions with a formally degenerate t12g electron configuration in the double-perovskite (DP) materials Ba2YMoO6, Ba2LiOsO6 and Ba2NaOsO6. Our analysis indicates that the sizable magnetic moments and g-factors found experimentally are due to both strong TM d – ligand p hybridization and dynamic Jahn-Teller effects. Our results also point out that cation charge imbalance in the DP structure allows a fine tuning of the gap between the t2g and eg levels. In another example of t12g electron configuration, spin-Peierls (SP) TiPO4 compound, we assign excitation peaks of experimental RIXS spectra and find that the d1 ground state is composed of an admixture of dz2 and dxz orbital character. In the second part, I will discuss a computational scheme for computing intensities as measured in X-ray absorption and RIXS experiments. We take into account the readjustment of the charge distribution in the 'vicinity' of an excited electron for the modeling of RIXS. The computed L3-edge RIXS spectra for Cu2+ 3d9 ions in KCuF3 and for Ni2+ 3d8 ions in La2NiO4 reproduce trends found experimentally for the incoming-photon incident-angle and polarization dependence.
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Particle Physics Seminar
"Measuring CCQE-like Cross Sections in MINERvA: when statistics meet precision"
Presented by Mateus F. Carneiro, Oregon State University
Thursday, February 14, 2019, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Elizabeth Worcester
MINERvA is a detector build to measure neutrino-nucleus cross sections. As we move towards more precise measurements, cross sections are of extreme importance to the future of neutrino physics. This talk will walk through all the steps necessary to simulate, select signal and measure a CCQE cross section while we test different nuclear models. New preliminary MINERvA results using the new configuration of the NuMI beam will be presented.
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RIKEN Lunch Seminar
"Chiral Photocurrents and Terahertz Emission in Dirac and Weyl Materials"
Presented by Mr. Sahal Kaushik, Stony Brook University
Thursday, February 14, 2019, 12 pm
Building 510, Room 2-160Hosted by: Yuta Kikuchi
Recently, chiral photocurrents have been observed in Weyl materials. We propose a new mechanism for photocurrents in Dirac materials in the presence of magnetic fields, that does not depend on any asymmetries of the crystal. This Chiral Magnetic Photocurrent would be an independent probe of the chiral anomaly. We also also discuss an observation of terahertz emission in the Weyl material TaAs with tunable ellipticity, due to chiral photocurrents induced by an ultrafast near infrared laser.
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Condensed-Matter Physics & Materials Science Seminar
"Resonant inelastic X-ray scattering (RIXS) as a probe of exciton-phonon coupling"
Presented by Andrey Geondzhian, European Synchrotron Radiation Facility (ESRF), France (UTC+1)
Thursday, February 14, 2019, 9:30 am
ISB Bldg. 734 Conference Room 201 (upstairs)Hosted by: Weiguo Yin
Phonons contribute to resonant inelastic X-ray scattering (RIXS) as a consequence of the coupling between electronic and lattice degrees of freedom. Unlike other techniques that are sensitive to electron-phonon interactions, RIXS can give access to momentum dependent coupling constants. This Information is highly desirable in the context of understanding anisotropic conventional and unconventional superconductivity. In my talk, I will consider the phonon contribution to RIXS from the theoretical point of view. In contrast to previous studies, we emphasize the role of the core-hole lattice coupling. Our model, with parameters obtained from first principles, shows that even in the case of a deep core-hole, RIXS probes exciton-phonon coupling rather than a direct electron-phonon coupling. Further, to address the needs of predictive approach and overcome limitations of the model studies we developed a Green's function formalism to capture electron-phonon contributions to RIXS and other core-level spectroscopies (X-ray photoemission spectroscopy (XPS), X-ray absorption spectroscopy (XAS)). Our approach is based on the cumulant expansion of the Green's function combined with many-body theory calculated vibrational coupling constants. In the case of the XAS and RIXS, we use a two-particle exciton Green's function, which accounts implicitly for particle-hole interference effects that have previously proved difficult. Finally, to demonstrate the methodology, we successfully applied our formalism to small molecules, for which unambiguous experimental data exist.
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Condensed-Matter Physics & Materials Science Seminar
"Phase transition in functional materials and structural dynamics as studied by UTEM"
Presented by Ming Zhang, Institute of Physics, Chinese Academy of Sciences
Tuesday, February 12, 2019, 10 am
ISB Bldg. 734 Conference Room 201 (upstairs)Hosted by: Jing Tao
My presentation contains 3 parts. First, I will briefly introduce the pump-probe technique and Ultrafast Transmission Electron Microscopy (UTEM). Then I will demonstrate our development project of the UTEM, including the modifications of the configuration, the establishment of optical system, the generation of photoelectrons, and specific cases are discussed to show the capability of our UTEM. At last, I will highlight the application of UTEM via two examples: (1) The photoinduced martensitic (MT) transition and reverse transition in a shape memory alloy Mn50Ni40Sn10 have been examined by UTEM, and imaging and diffraction observations clearly show a variety of structural dynamic features at picosecond time scales; (2) The Lorentz UTEM for direct imaging photoinduced ultrafast magnetization dynamics, revealing remarkable features of magnetic transient states after a femtosecond pulsed laser excitation, and three successive dynamical processes involving four distinct magnetic states are evidently observed in MnNiGa crystals.
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NT / RIKEN Seminar
"Realizing relativistic dynamics with slow light polaritons at room temperature"
Presented by Eden Figueroa, Stony Brook University
Friday, February 8, 2019, 2 pm
CFNS Seminar RoomHosted by: Niklas Mueller
Experimental verification of relativistic field theory models requires accelerator experiments. A possible pathway that could help understanding the dynamics of such models for bosons or fermions is the use of quantum technology in the form of quantum analog simulators. In this talk we will explore the possibility of generating nonlinear Dirac-type Hamiltonians using coherent superpositions of photons and spin wave excitations of atoms. Our realization uses a driven slow-light setup, where photons mimic the Dirac fields and different dynamics can be implemented and tuned by adjusting optical parameters. We will show our progress tin building a quantum simulator of the Jackiw-Rebbi model using highly-interacting photons strongly coupled to a room temperature atomic ensemble. We have identified suitable conditions in which the input photons dispersion relations can be tuned to a spinor of light configuration, mimicking the Dirac regime and providing a framework to create tunable interactions and varying mass terms. Lastly, we will show our vision to scale these ideas to multiple interacting fermions.
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RIKEN Lunch Seminar
"Modification of the nucleon-nucleon potential and nuclear correlations due to the QCD critical point"
Presented by Juan M. Torres-Rincon, Stony Brook University
Thursday, February 7, 2019, 12 pm
Building 510, Room 2-160Hosted by: Enrico Rinaldi
The scalar-isoscalar mode of QCD becomes lighter/nearly massless close to the chiral transition/second-order critical point. This mode is the main responsible for the attractive part of the nucleon-nucleon potential at distances of 1-2 fm. Therefore, a long-range strong attraction among nucleons is predicted to develop close to the QCD critical point. Using the Walecka-Serot model for the NN potential we study the effects of the critical mode in a system of nucleons and mesons using a Molecular Dynamics+Langevin equations for the freeze-out conditions of heavy-ion collisions. Beyond mean field, we observe strong nucleon correlations leading to baryon clustering. We propose that light-nuclei formation, together with an enhancement of cumulants of the proton distribution can signal the presence of the QCD critical point.
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Condensed-Matter Physics & Materials Science Seminar
"Stimulation of quantum phases by time-dependent perturbations"
Presented by Victor Galitski, University of Maryland
Thursday, February 7, 2019, 11 am
ISB Bldg. 734, Conf. Room 201 (upstairs)Hosted by: Mark Dean
I will review our theory work on dynamic stimulation of various quantum phases. A key idea here is that the equilibrium distribution is rarely optimal for occurrence of a given quantum state and dynamic perturbations can be used to "deform" an electron population in a favorable way in order to enhance quantum coherence. To illustrate this idea, I will show how both Cooper pairing and phase coherence can be dynamically enhanced in both conventional superconductors and bosonic superlfuids. Then, I will discuss dynamic enhancement of high-temperature superconductivity in the cuprates, as it reported in experiments by the Andrea Cavalleri group in Hamburg. It will be shown that an optical pump can suppress charge order and simultaneously enhance superconductivity, due to the inherent competition between the two. In the second part of my talk, I will generalize these ideas to quantum cavities, where the light-matter coupling can be strongly enhanced. In particular, I will discuss the hybridization of cavity photons with collective modes in interacting two-dimensional materials, including the formation of Higgs polaritons and the closest analogue to excitons in a superconductor - Bardasis-Schrieffer modes - hybridized with light.
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Condensed-Matter Physics & Materials Science Seminar
"Novel Electrochemistry for Fuel Cell Reactions: Efficient Synthesis and New Characterization Methods"
Presented by Zhixiu Liang
Wednesday, February 6, 2019, 4:30 pm
Bldg. 480 Conference RoomHosted by: Jing Tao
The ever increasing consumption of fossil fuels for transportation causes climate change causing a growing concern about their future availability and further adverse environmental effects. To address this issue, the concept of CO2 neutral fuels-based energy cycle was brought out. The key reactions in that concept are electrochemical methanol oxidation (MOR), ethanol oxidation reaction (EOR), and CO2 reduction reaction (CO2RR). These all are elctrocatalysis research challenges being slow even at the best catalyst that hamper application of fuel cells, and bring environmental benefits. My research made these improvements of catalysts for the key reactions. In-situ electrochemical infrared reflective absorbance spectrum (EC-IRRAS) reveals that at lower temperature, such reaction is not complete and generates more formate; at elevated temperature, such reaction is complete to carbonate. Ethanol is one of the ideal fuels for fuel cells, but requires highly improved catalysts. Au@PtIr/C catalyst was synthesized with a surfactant-free wet-chemistry approach. Transmission electron microscope (TEM) characterization confirms the monolayer/sub-monolayer Pt-Ir shell, gold core structure. The catalyst has a very high mass activity of 58 A/mg at peak current. In situ EC-IRRAS reveals that C-C bond is cleaved upon contact with the catalyst surface leading to ethanol complete oxidation to CO2. Related researches on methodologies, included in situ TEM to help obtaining catalysts improvements, give morphologic, structural and spectroscopic information at wide range from hundreds of microns to sub-nanometer coupled with various detectors. Microelectromechanical System (MEMS) based chips technology enables TEM observation in operando, with liquid-flow-cell chips and electrochemistry chips designed and fabricated. Ag@Au hollow cubes synthesis via galvanic replacement of Au on Ag cubes was investigated with in situ TEM. The results demonstrate abnormal react
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Nuclear Physics Seminar
"Probing the Sea Quark Polarization at RHIC/STAR"
Presented by Jinlong Zhang, Stony Brook University
Tuesday, February 5, 2019, 11 am
Small Seminar Room, Bldg. 510Hosted by: Oleg Eyser
Polarized proton-proton collision experiments at RHIC have provided unique opportunities to study the spin structure of the nucleon. One of the primary motivations of RHIC spin program is to probe sea quark spin-flavor structure via W-boson production in proton-proton collisions at a center of mass energy of 500 GeV. Measurements of the longitudinal single-spin asymmetry, A_L, of W-bosons with the STAR detector have provided significant constraints on the polarized parton distribution functions and especially the first experimental indication of a flavor asymmetry of polarized sea. In this seminar, I will present the analyses and latest results from STAR, as well as their impact on our knowledge of the sea quark helicity distributions.
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RIKEN Lunch Seminar
"Sorting out jet quenching in heavy-ion collisions"
Presented by Jasmine Brewer, Massachusetts Institute of Technology
Thursday, January 31, 2019, 12 pm
Building 510, Room 2-160Hosted by: Enrico Rinaldi
We introduce a new "quantile'' analysis strategy to study the modification of jets as they traverse through a droplet of quark-gluon plasma. To date, most jet modification studies have been based on comparing the jet properties measured in heavy-ion collisions to a proton-proton baseline at the same reconstructed jet transverse momentum pT. It is well known, however, that the quenching of jets from their interaction with the medium leads to a migration of jets from higher to lower pT, making it challenging to directly infer the degree and mechanism of jet energy loss. Our proposed quantile matching procedure is inspired by (but not reliant on) the approximate monotonicity of energy loss in the jet pT. In this strategy, jets in heavy-ion collisions ordered by pT are viewed as modified versions of the same number of highest-energy jets in proton-proton collisions. Despite non-monotonic fluctuations in the energy loss, we use an event generator to validate the strong correlation between the pT of the parton that initiates a heavy-ion jet and the pT of the vacuum jet which corresponds to it via the quantile procedure. We demonstrate that this strategy both provides a complementary way to study jet modification and mitigates the effect of pT migration in heavy-ion collisions.
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Environmental & Climate Sciences Department Seminar
"What can we learn from cloudy convection in a box? Laboratory meets LES with cloud microphysics"
Presented by Raymond Shaw, MTU
Thursday, January 31, 2019, 11 am
Conference Room Bldg 815EHosted by: Fan Yang
Inspired by early convection-tank experiments (e.g., Deardorff and Willis) and diffusion-chamber experiments, we have developed a cloud chamber that operates on the principle of isobaric mixing within turbulent Rayleigh-Bénard convection. The "Pi cloud chamber" has a height of 1 m and diameter of 2 m. An attractive aspect of this approach is the ability to make direct comparison to large eddy simulation with detailed cloud microphysics, with well characterized boundary conditions, and statistical stationarity of both turbulence and cloud properties. Highlights of what we have learned are: cloud microphysical and optical properties are representative of those observed in stratocumulus; aerosol number concentration plays a critical role in cloud droplet size dispersion, i.e., dispersion indirect effect; aerosol-cloud interactions can lead to a condition conducive to accelerated cloud collapse; realistic and persistent mixed-phase cloud conditions can be sustained; LES is able to capture the essential features of the turbulent convection and warm-phase cloud microphysical conditions. It is worth considering what more could be learned with a larger-scale cloudy-convection chamber. Turbulence Reynolds numbers and Lagrangian-correlation times would be scaled up, therefore allowing more enhanced role of fluctuations in the condensation-growth process. Larger vertical extent (of order 10 m) would approach typical collision mean free paths, thereby allowing for direct observation of the transition from condensation- to coalescence-growth. In combination with cloudy LES, this would be an opportunity for microphysical model validation, and for synergistic learning from model-measurement comparison under controlled experimental conditions.
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Condensed-Matter Physics & Materials Science Seminar
"Strongly-correlated systems: Controllable field-theoretical approach"
Presented by Igor Tupitsyn, University of Massachusetts Amherst
Tuesday, January 29, 2019, 1:30 pm
ISB Bldg. 734, Conf. Rm. 201 (upstairs)Hosted by: Alexei Tsvelik
Accurate account for interactions in theoretical models for strongly correlated many-body systems is the key for understanding real materials and one of the major technical challenges of modern physics. To accept this challenge, new and more effective methods, capable of dealing with interacting systems/models in an approximation-free manner, are required. One of such methods is the field-theoretical Diagrammatic Monte Carlo technique (DiagMC). While a conventional Quantum Monte Carlo samples the configuration space of a given model Hamiltonian, the DiagMC samples the configuration space of the model-specific Feynman diagrams and obtains final results with controlled accuracy by accounting for all the relevant diagrammatic orders. In contrast to conventional QMC, it does not suffer from the fermionic sign problem and can be applied to any system with arbitrary dispersion relation and shape of the interaction potential (both doped and undoped). In the first part of my talk I will introduce the technique, based on its bold-line (skeleton) implementation, and benchmark it against known results for the problem of semimetal-insulator transition in suspended graphene. In the second part I will briefly demonstrate its applications to various strongly-correlated systems/problems (stability of the 2d Dirac liquid state against strong long-range Coulomb interaction; interacting Chern insulators; phonons in metals; 1d chain of hydrogen atoms; uniform electron gas (jellium model), optical conductivity, etc).
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Nuclear Physics Seminar
"Measurements and Calculations of $\hat{q}L$ via transverse momentum broadening in RHIC collisions using di-hadron correlations"
Presented by Michael Tannenbaum, BNL
Tuesday, January 29, 2019, 11 am
Small Seminar Room, Bldg. 510Hosted by: Jin Huang
The renewed interest in analyzing RHIC data on di-hadron correlations as probes of final state transverse broadening as shown at Quark Matter 2018 by Miklos Gyulassy citing theoretical calculations compared to experimental measurements which didn't look right on Miklos' figure led me to take a closer look at this issue using published PHENIX data . The measured values of $\hat{q}L$ show the interesting effect of being consistent with zero for values of the associated particle transverse momentum pTa >3 GeV/c. This is shown to be related to the well-known effect of the variable IAA, the ratio of the Au+Au to p+p pTa distributions for a given trigger pTt.
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Nuclear Theory / RIKEN Seminar
"Effective field theory of hydrodynamics"
Presented by Paolo Glorioso, Kadanoff Center for Theoretical Physics and Enrico Fermi Institute, University of Chicago
Friday, January 25, 2019, 2 pm
CFNS Seminar Room 2-38Hosted by: Niklas Mueller
I will give an overview of our work on developing an effective field theory of dissipative hydrodynamics. The formulation is based on the Schwinger-Keldysh formalism, which provides a functional approach that naturally includes dissipation and fluctuations. Hydrodynamics is implemented by introducing suitable degrees of freedom and symmetries. I will then discuss two important by-products. First, the second law of thermodynamics, which in the traditional approach is imposed at phenomenological level, is here obtained from a basic symmetry principle together with constraints from unitarity. Second, I will show consistency with unitarity and causality of the hydrodynamic path-integral at all loops, which leads to the first systematic framework to compute hydrodynamic fluctuations.
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RIKEN Lunch Seminar
"Quarkonium production in heavy ion collisions: open quantum system, effective field theory and transport equations"
Presented by Xiaojun Yao, Duke University
Thursday, January 24, 2019, 12 pm
Building 510, Room 1-224Hosted by: Yuta Kikuchi
In this talk, I will present a connection between two approaches of studying quarkonium dynamics inside quark-gluon plasma: the open quantum system formalism and the transport equation. I will discuss insights from the perspective of quantum information. I will show that under the weak coupling and Markovian approximations, the Lindblad equation turns to a Boltzmann transport equation after a Wigner transform is applied to the system density matrix. I will demonstrate how the separation of physical scales justifies the approximations, by using effective field theory of QCD. Finally, I will show some phenomenological results based on the derived transport equation.
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Instrumentation Division Seminar
"A Roadmap for the Best PMTs and SiPM in Physics Research"
Presented by Razmik Mirzoyan, Max Planck Institute for Physics, Germany
Wednesday, January 23, 2019, 2:30 pm
Large Conference Room, Bldg. 535Photomultiplier Tubes (PMT) are the most wide spread detectors for measuring fast and faint light signals. In cooperation with the companies Hamamatsu Photonics K.K. (Japan) and Electron Tubes Enterprises Ltd. (England) we pursued an improvement program for the PMTs for the Cherenkov Telescope Array (CTA) project. CTA is the next major Imaging Atmospheric Cherenkov Telescopes (IACT) array for ground-based very high energy gamma-ray astrophysics. A total of ∼100 telescopes of sizes of 23m, 12m and 4m in diameter will be built in northern and southern hemispheres. The manufacturers succeeded producing 1.5′ PMTs of enhanced peak quantum efficiency of ∼38-42 % and after pulsing below 0.02% (threshold ≥ 4 photoelectrons). The novel 1.5′ PMTs have the world-wide best parameters. It is interesting to compare the performance of PMTs with the current generation of SiPMs. In the imaging camera of the MAGIC IACT, consisting of 1039 PMTs, since many months we are operating composite clusters of SiPMs from the three well-known manufacturers. A critical comparison of these two types of sensors will be presented. Prospects for further significant improvements of PMTs and SiPMs will be discussed, also in the frame of the supported by the EU SENSE Roadmap for the best fast light sensors.
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Condensed-Matter Physics & Materials Science Seminar
"Recent Progress in Non-perturbative methods for QFTs"
Presented by Lorenzo Vitale, Boston University
Wednesday, January 23, 2019, 1:30 pm
ISB Bldg. 734 Conf. Rm. 201 (upstairs)Hosted by: Alexei Tsvelik
Quantum field theories (QFT) are notoriously hard to solve in the strongly coupled regime, and few tools are available in space dimension larger than one. In this talk I discuss recent progress and ideas in characterizing certain QFTs in dimension d >= 1, based on the Hamiltonian Truncation and S-matrix bootstrap techniques. Some of the applications I will mention are Landau-Ginzburg theories and the Chern-Simons-matter theories.
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Particle Physics Seminar
"Exploring the HEP frontier with the Cosmic Microwave Background and 21cm cosmology"
Presented by Laura Newburgh, Yale University
Friday, January 18, 2019, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Anze Slosar
Current cosmological measurements have left us with deep questions about our Universe: What caused the expansion of the Universe at the earliest times? How many standard model particles are there? What is the underlying nature of Dark Energy and dark matter? New experiments like CMB-StageIV, Simons Observatory, and CHIME are poised to address these questions through measurements of the polarized Cosmic Microwave Background and 3-dimensional maps of structure. In this talk, I will describe efforts in the community to deploy enormous experiments that are capable of turning CMB measurements into probes of high energy particle physics. I will also discuss how we can broaden the potential science returns by including 21 cm measurements of large scale structure as a new means to probe Dark Energy with experiments like CHIME and HIRAX.
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Nuclear Theory / RIKEN Seminar
"Chiral Vortical Effect For An Arbitrary Spin"
Presented by Andrey Sadofyev, Los Alamos National Lab
Friday, January 18, 2019, 2 pm
CFNS Seminar Room 2-38Hosted by: Niklas Mueller
Chiral effects attracted significant attention in the literature. Recently, a generalization of chiral vortical effect (CVE) to systems of photons was suggested. In this talk I will discuss the relation of this new transport to the topological phase of photons and show that, in general, CVE can take place in rotating systems of massless particles with any spin.
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Instrumentation Division Seminar
"Timing circuits for high-energy physics applications"
Presented by Jeffrey Prinzie, KU Leuven University, Belgium
Friday, January 18, 2019, 11 am
Large Conference Room, Bldg. 535In the era of complex systems on chip (SoCs), clock and timing generation is required in nearly any application. These timing generators supply clock signals to digital modules, act as heartbeats for serial communication links or provide picosecond accurate reference information to time-interval sensors. Phase Locked Loops are the main building block that provide clock signals. However, in the high-energy physics community, ionizing radiation effects degrade these circuits significantly and produce soft-errors which can disturb an entire system. In this seminar, the application of these timing blocks in the high-energy physics are discussed together with the mitigation techniques for ionizing radiation.
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RIKEN Lunch Seminar
"Proton decay matrix elements on lattice"
Presented by Mr. Jun-sik Yoo, Stony Brook University
Thursday, January 17, 2019, 12 pm
Building 510, Room 2-160Hosted by: Enrico Rinaldi
Proton decay is one of possible signatures of baryon number violation, which has to exist to explain the baryon asymmetry and the existence of nuclear matter. Proton decay is one of natural implications of the Grand Unification Theory. After integrating out the high energy degrees of freedom, the baryon number violation operator that mediates proton decay can be found as the composite operator of standard model fields. We discuss the hadronic matrix elements of this BV operator made of three quarks and a lepton. We will start from the current experimental bound of proton lifetime. We present preliminary results of matrix element calculation done with the 2+1 dynamical flavor domain wall fermions at the physical point. We will discuss the proton decay channels that no matrix element has been calculated on the lattice.
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Condensed-Matter Physics & Materials Science Seminar
"Effect of ion irradiation on the mechanical behavior and microstructural evolution of nanoscale metallic alloys"
Presented by Gowtham Sriram Jawaharram, University of Illinois at Urbana - Champaign
Wednesday, January 16, 2019, 11 am
ISB Bldg. 734 Conference Room 201 (upstairs)Hosted by: Jing Tao
Nanostructured alloys are considered as potential candidates for next generation (Generation IV) nuclear reactors because the high densities of interfacial defect sinks present in these materials. The effect of irradiation on the mechanical behavior of such alloys has received limited attention, likely resulting from the experimental challenges associated with performing such experiments. The first part of the talk will report on our recent efforts to perform high temperature irradiation induced creep (IIC) measurements in focused ion beam fabricated FCC alloys (single crystalline Ag nanopillars and nanocrystalline high entropy alloys (HEA) microbeams) by combining in-situ TEM based small-scale mechanical testing with ion irradiation and in-situ laser heating using the in-situ ion irradiation transmission electron microscope (I3TEM) at Sandia National Laboratories. The effect of pillar size, grain size, and temperature on the observed creep mechanism will be discussed. The second part of the talk will focus on the microstructural evolution of model highly immiscible CuW alloys during thermal annealing and high temperature irradiation characterized using high angle annular dark field (HAADF) imaging. The results will be discussed from the context of evolution and spatial distribution of W precipitates and its effect on hardness as a function of irradiation dose and temperature.
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Physics Colloquium
"Liquid Argon Detectors and Readout Electronics: From R&D to Physics Discovery"
Presented by Hucheng Chen, BNL
Tuesday, January 15, 2019, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Andrei Nomerotski
BNL has a long history of R&D in noble liquid based detectors, from the invention of the first liquid argon (LAr) calorimeter in 1974, to the construction of large liquid argon time projection chambers (LAr TPC) leading to Deep Underground Neutrino Experiment (DUNE) by 2026, in a time span over half a century. Readout electronics has always been an integral part of the detector, in both ATLAS LAr Calorimeter where high precision has played an essential role in the 2012 Higgs discovery, and in LAr TPC based neutrino detectors where cryogenic electronics proved to be an enabling technology. The development of noble liquid based detectors and readout electronics systems at BNL will be presented, focused on integrated detector-readout design, as motivated by our physics interests and experiment requirements, in energy frontier LHC experiments, and in intensity frontier short baseline and long baseline neutrino experiments. As both experiments present challenges in data acquisition, the FELIX based DAQ system for high-bandwidth detector readout developed at BNL, also being adopted in various particle physics experiments worldwide, will be discussed as well.
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Particle Physics Seminar
"Cross section measurements and new physics searches with WZ vector boson scattering events at CMS"
Presented by Kenneth Long, University of Wisconsin - Madison
Thursday, January 10, 2019, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Alessandro Tricolli
As the standard model (SM) Higgs boson looks increasingly like its SM expectation, expanded tests of the electroweak (EW) sector of the SM are a focal point of the long-term LHC program. Production of massive vector bosons via vector boson scattering provides a direct probe of the self-interactions of the massive vector bosons, which are intimately connected to the Higgs-Englert-Brout mechanism of EW symmetry breaking. A search for vector boson scattering of W and Z bosons has recently been performed by the CMS experiment using data collected in 2016. I will present this search as well as WZ cross section measurements, which are less dependent on theoretical inputs. This process is also sensitive to New Physics in the EW sector. I will present interpretations of these results in terms of explicit models predicting additional charged Higgs bosons and in the generalized framework of dimension-8 effective field theory.
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Condensed-Matter Physics & Materials Science Seminar
"Exact Solution and Semiclassical Analysis of BCS-BEC Crossover in One Dimension"
Presented by Tianhao Ren, Columbia University
Monday, January 7, 2019, 1:30 pm
ISB Bldg. 734 Conf. Rm. 201 (upstairs)Hosted by: Alexei Tsvelik
In this talk, I will introduce a new type of model for two-component systems in one dimension subject to exact solutions by Bethe ansatz. It describes the BCS-BEC crossover in one dimension and its integrability is obtained by fine-tuning the model parameters. The new model has rich many-body physics, where the Fermi momentum for the ground state distribution is constrained to be smaller than a certain value and the zero temperature phase diagram with an external field has a critical field strength for polarization. Also the low energy excitation spectra of the new model present robust features that can be related to solitons at BCS-BEC crossover in one dimension, as shown by the semiclassical analysis.
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Particle Physics Seminar
"DM-Ice17 and COSINE-100 NaI(Tl) Dark Mater Experiment: Testing DAMA's Claim for a Dark Matter Discovery"
Presented by Jay Hyun Jo, Yale University
Thursday, January 3, 2019, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Chao Zhang
Astrophysical observations give overwhelming evidence for the existence of dark matter, yet we do not know what it is. For over 20 years, the DAMA collaboration has asserted that they observe a dark matter-induced annual modulation signal but their observation has yet to be confirmed by an independent measurement. DM-Ice17 is a prototype experiment consisting of 17 kg of NaI(Tl) detectors to test the DAMA's claimed detection of the dark matter annual modulation, which has been continuously operating at the South Pole since 2011. COSINE-100 is a joint experiment between DM-Ice and KIMS collaboration, situated at the Yangyang Underground Laboratory in South Korea. COSINE-100 consists of eight low background NaI(Tl) crystals with a total mass of 106 kg and 2000 liters of liquid scintillator as an active veto, and the physics run of the experiment began in September 2016. The recent results from DM-Ice17 and COSINE-100, including the status of the field, will be presented.
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Instrumentation Division Seminar
"Data Acquisition Systems for High-Speed and High-Dynamic Range Pixel Array Detectors"
Presented by Prafull Purohit, Cornell University
Friday, December 28, 2018, 10:30 am
Large Conference Room, Bldg. 535Pixel array detectors (PADs) have seen significant increase in performance and operational complexity in recent years due to advances in microelectronics technology and photon science needs. These advances in detector technology put equal complexity and performance requirements on the data acquisition and control systems for successful operation. A Field Programmable Gate Array (FPGA) with its high-speed processing and reconfiguration capabilities can be utilized to meet current requirements and future needs. In this talk, I will present some of the recent work done at Cornell University on FPGA-based data acquisition systems for high-speed, high dynamic range detectors as well as detectors for time resolved experiments.
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Particle Physics Seminar (Leona Woods Distinguished Postdoctoral Lectureship Award)
"Measurement of top quark pair production in association with a Higgs or gauge boson at the LHC with the ATLAS detector"
Presented by María Moreno Llácer, CERN
Thursday, December 20, 2018, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Alessandro Tricoli
The top quark is unique among the known quarks since it decays before it has an opportunity to form hadronic bound states. This makes measurements of its properties particularly interesting as one can access directly the properties of a bare quark. Given its large mass (the heaviest fundamental particle), the top quark may play a special role in the electroweak symmetry breaking mechanism and therefore, new physics related to this might be found first in top quark precision measurements. Possible new physics signals would cause deviations of the top quark couplings from the Standard Model (SM) prediction. It couples to the SM fields through its gauge and Yukawa interactions. The high statistics top quark sample at the LHC has allowed to access the associated production of a top quark pair with a boson: tt+photon, tt+W, tt+Z and tt+H. The latest measurements carried out by the ATLAS detector for these physics processes will be presented, highlighting the main challenges.
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Physics Colloquium (Leona Woods Distinguished Postdoctoral Lectureship Award)
"On top of the top: challenging the Standard Model with precise measurements of top quark properties"
Presented by María Moreno Llácer, CERN
Tuesday, December 18, 2018, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Andrei Nomerotski
The understanding of the Electro-Weak Symmetry Breaking mechanism and the origin of the mass of fundamental particles is one of the most important questions in particle physics today. The top quark is unique among the known quarks since it is the heaviest fundamental particle in the Standard Model. Its large mass makes the top quark very different from all other particles, with a Yukawa coupling to the Higgs boson close to unity. For these reasons, the top quark and the Higgs boson play very special roles in the SM and in many extensions thereof. An accurate knowledge of their properties can bring key information on fundamental interactions at the electroweak breaking scale and beyond. The Large Hadron Collider is providing an enormous dataset of proton-proton collisions at the highest energies ever achieved in a laboratory. With the unprecedentedly large sample of top quarks, a new frontier has opened, the flavour physics of the top quark, allowing to study whether the Higgs field is the unique source of the top quark's mass and whether there are unexpected interactions between the top quark and the Higgs boson. The answers to these questions will shed light on what may lie beyond the Standard Model and can even have cosmological implications.
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Condensed-Matter Physics & Materials Science Seminar
"Uncovering the interactions behind quantum phenomena"
Presented by Keith Taddei, Oak Ridge National Laboratory
Tuesday, December 18, 2018, 11 am
ISB Bldg. 734, Conf. Rm. 201 (upstairs)Hosted by: Ian Robinson/Mark Dean
Quantum computing, spintronics and plasmonics are nascent fields with potential to radically change our technological landscape. Fundamental to advancing these technologies is a mastery of quantum materials such as superconductors, quantum-spin-liquids and multiferroics. Ideally, we would know exactly what interactions give rise to these phenomena and design materials suitable for applications however, such an understanding as of yet eludes us. Instead we are stuck digging around in the phase space of known quantum materials slowly uncovering pertinent details to their design, filling in pieces of our incomplete picture. In this presentation, I will discuss recent bits I have found in my use of neutron scattering to study quantum materials. Starting with a novel new family of quasi-one-dimensional (Q1D) superconductors (A1,2TM3As3 with A = alkali metal and TM = Cr, Mo) I will present findings of short-range structural order and a proximate magnetic instability which, due the radically different structure, allow for new insights to the pertinence to such orders to superconductivity. Importantly, in these materials the two orders break different symmetries and so their interactions with the superconducting order can be studied independently. Next, I will discuss an interesting yet neglected family of frustrated magnetic materials – the rare-earth pyrogermanates (REPG). We find the Er2Ge2O7 REPG to exhibit 'local-Ising' type magnetism in direct analogy to the spin-ice pyrochlores suggesting effects of local anisotropies and dipole interactions. Finally, I will present ongoing work investigating spin-driven polarization effects in the magnetically and structurally straightforward multiferroic BiCoO3. These results demonstrate the essential role of neutron and x-ray scattering techniques in studying these complex materials and the fruitful opportunities these systems present to advance our understanding of quantum materials.
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Physics Colloquium
"The Science of the Sudbury Neutrino Observatory (SNO) and SNOLAB"
Presented by Art McDonald, Queens University
Monday, December 17, 2018, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: David Asner
A description of the science associated with the Sudbury Neutrino Observatory, performed with substantial contributions from BNL scientists, and its relation to other neutrino measurements will be given, along with a discussion of the new set of experiments that are at various stages of development or operation at SNOLAB. These experiments will perform measurements of neutrino properties and seek direct detection of Weakly-Interacting Massive Particles (WIMPS) as Dark Matter candidates. Specific examples will include SNO+ (with BNL participation), in which the central element of the SNO detector will now be liquid scintillator with Te dissolved for neutrino-less double beta decay and DEAP-3600 using liquid argon for single phase direct Dark Matter detection. Future directions for Dark Matter detection with liquid argon will also be discussed.
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NT/RIKEN Seminar
"Lattice QCD Input for Fundamental Symmetry Tests"
Presented by Micheal Wagman, MIT
Friday, December 14, 2018, 2 pm
Building 510, Room 2-38Hosted by: Niklas Mueller
Experimental detection of fundamental symmetry violation would provide a clear signal for new physics, but theoretical predictions that can be compared with data are needed in order to interpret experimental results as measurements or constraints of beyond the Standard Model physics parameters. For low-energy experiments involving protons, neutrons, and nuclei, reliable theoretical predictions must include the strong interactions of QCD that confine quarks and gluons. I will discuss experimental searches for neutron-antineutron oscillations that test beyond the Standard Model theories of matter-antimatter asymmetry with low-scale baryon-number violation. Lattice QCD can be used to calculate the neutron-antineutron transition rate using a complete basis of six-quark operators describing neutron-antineutron oscillations in effective field theory, and I will present the first lattice QCD results for neutron-antineutron oscillations using physical quark mass simulations and fully quantified uncertainties. Other experiments searching for neutrinoless double-beta decay and dark matter direct detection use large nuclear targets that are more difficult to simulate in lattice QCD because of an exponentially difficult sign(al-to-noise) problem. I will briefly describe the state-of-the-art for lattice QCD calculations of axial, scalar, and tensor matrix elements relevant to new physics searches with nuclei and outline my ongoing efforts to improve signal-to-noise problems using phase unwrapping.
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Condensed-Matter Physics & Materials Science Seminar
"Discussion of opportunities related to Quantum Information initiative"
Presented by Alexei Tsvelik, BNL
Friday, December 7, 2018, 3 pm
ISB Bldg. 734, Conf. Rm. 201 (upstairs)Alexei Tsvelik will be sharing his thoughts on how we can answer to the DOE initiative on Quantum Information
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NSLS-II Friday Lunchtime Seminar
"Magnetic skyrmions at room temperature - statics, dynamics, and high resolution imaging"
Presented by Dr. Felix Buttner, Dept of Mat Sci & Eng , MIT
Friday, December 7, 2018, 12 pm
NSLS-II Bldg 743 Room 156Hosted by: Ignace Jarrige
Magnetic skyrmions are the smallest non-trivial entities in magnetism with great potential for data storage applications. These chiral and topological quasi-particles furthermore exhibit fascinating static and dynamical properties that render them the ideal candidates to study new physics in high spin-orbit coupling materials. In this talk, I will first give a general introduction to the field of skyrmionics and the fundamental properties of skyrmions that derive from their energetics. I will then discuss various ways of creating and stabilizing room-temperature skyrmions experimentally, as well as how we can move them and observe their topological dynamics via high resolution time-resolved x-ray imaging. I will conclude with perspectives of future research in this field and related areas.
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Particle Physics Seminar
"The Global Electroweak Fit in the light of the new results from the LHC"
Presented by Matthias Schott, University of Mainz
Thursday, December 6, 2018, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Alessandro Tricoli
With the high integrated luminosities recorded at the LHC and the very good understanding of the LHC detectors, it is possible to measure electroweak observables to the highest precision. In this talk, I review the measurement of the W boson mass as well as the measurement of the electroweak mixing angle with the ATLAS detector, both achieving highest precision after several years of intense effort. Special focus is drawn on a discussion of the modeling uncertainties as well as the physics potential of the latest low-mu runs, recorded at in 2017 and 2018. The results will be interpreted in terms of the overall consistency of the Standard Modell by the global electroweak fit, performed by the Gfitter Collaboration.
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Condensed-Matter Physics & Materials Science Seminar
"Laser induces dynamics in complex oxides with visible/NIR and X-ray probe (Note: This will be a skype presentation)"
Presented by Sergii Parchenko, Swiss Light Source, Paul Scherrer Institute, Switzerland
Tuesday, December 4, 2018, 11 am
ISB Bldg. 734, Conf. Rm. 201 (upstairs)Hosted by: Ian Robinson/Mark Dean
**********Note: This will be a Skype Presentation************ recent achievements in generation of ultrashort and intense light pulses allow observation of the physical process on the ultrafast regime. exploring fundamental physical processes on the time scales of interactions, responsible for them, is the key for future understanding of the physical principles and implementation then to the technological application. with this talk, i'm going to present the study of laser induced dynamics in complex oxides with focus on several physical objects: magnetic exchange interaction, insulator to metal transition and magneto-electric coupling. it will be discussed how the study of laser induced changes with different probing methods could help to understand the microscopic mechanisms of physical processes on the ultrafast time scale.
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Condensed-Matter Physics & Materials Science Seminar
"First-principles description of correlated materials with strong spin-orbit coupling: the analytic continuation and branching ratio calculation"
Presented by Jae-Hoon Sim, Department of Physics, KAIST, Korea, Republic of (South)
Monday, December 3, 2018, 1:30 pm
ISB Bldg. 734 Conf. Rm. 201 (upstairs)Hosted by: Sangkook Choi
The DFT+DMFT combined with the continuous-time quantum Monte Carlo (CT-QMC) impurity solver is one of the successful approaches to describe correlated electron materials. However, analytic continuation of the QMC data written in the imaginary frequency to the real axis is a difficult numeric problem mainly due to the ill-conditioned kernel matrix. While the maximum entropy method is one of the most suitable choices to gain information from the noisy input data, its applications to the materials with strong spin-orbit coupling are limited by the non-negative condition of the output spectral function. In the first part of this talk, I will discuss the newly developed methods for analytic continuation problem, the so-called maximum quantum entropy method (MQEM) [1]. It is the extension of the conventional method, introducing quantum relative entropy as a regularization function. The application of the MQEM for a prototype j_eff=1/2 Mott insulator, Sr2IrO4, shows that it provides a reasonable band structure without introducing a material specific base set. I will also introduce the application of machine learning technique to the same problem [2]. In the second part, a simple technique to branching ratio from the first-principles calculation will be discussed [3]. The calculated ?L·S? and branching ratio of the different 5d iridates, namely Sr2IrO4, Sr2MgIrO6, Sr2ScIrO6, and Sr2TiIrO6 are in good agreement with recent experimental data. Its reliability and applicability also be carefully examined in the recent study. [1] J.-H. Sim and M. J. Han, Phys. Rev. B 98, 205102 (2018). [2] H. Yoon, J.-H. Sim, and M. J. Han, Phys. Rev. B (in press). [3] J.-H. Sim, H. Yoon, S. H. Park, and M. J. Han, Phys. Rev. B 94, 115149 (2016).
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Condensed-Matter Physics & Materials Science Seminar
"Localized-to-itinerant crossovers in Kondo materials"
Presented by Daniel Mazzone, Brookhaven National Laboratory, NSLS-II
Monday, December 3, 2018, 11 am
ISB Bldg. Conf. Room 201 (upstairs)Hosted by: Ian Robinson/Mark Dean
While charge carriers in crystalline structures can be located close to the nuclei or establish a delocalized character, they often epitomize strong fluctuations at intermediate regimes where emergent quantum phases show an intricate coupling among various degrees of freedom. Kondo materials are particularly interesting model systems to investigate strongly correlated phenomena, because they often possess small energy scales that are highly susceptible to macroscopic constraints. I will present recent neutron and X-ray scattering results on the series Nd1-xCexCoIn5 and Sm1-xYxS, where the ground state properties were tuned either via chemical substitution or magnetic field. We find that Nd substitution in CeCoIn5 affects the magnetic coupling parameters, triggering a change in the magnetic symmetry that is offset from the emergence of coherent heavy bands and unconventional superconductivity. Intriguingly, another magneto-superconducting phase with altered coupling is observed in Nd0.05Ce0.95CoIn5 at large magnetic fields. Sm1-xYxS features a transition towards an intermediate valence state under yttrium doping. Our results unravel a Kondo-triggered Lifshitz-transition in the mixed-valence state, which dives an unusually strong charge localization at low temperatures.
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Nuclear Theory / RIKEN Seminar
"Novel probes of small-x QCD"
Presented by Juan Rojo, VU University
Friday, November 30, 2018, 2 pm
CFNS Seminar Room 2-38Hosted by: Niklas Mueller
The small Bjorken-x regime of QCD is of great interest since a variety of different phenomena are known or expected to emerge, from BFKL small-x effects and non-linear and saturation dynamics to shadowing corrections in heavy nuclei. In this talk we present recent developments in our understanding of perturbative and non-perturbative QCD at small-x: the evidence for BFKL dynamics in the HERA structure function data, the precision determination of collinear PDFs from charm production at LHCb, and the first results on neural-network based fits of nuclear PDFs. We also highlight the remarkable connection between small-x QCD and high-energy astrophysics, in particular for the theoretical predictions of signal and background event rates at neutrino telescopes such as IceCube and KM3NET
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Particle Physics Seminar
"The structure of the proton in the LHC precision era"
Presented by Juan Rojo, Vrije Universiteit Amsterdam and Nikhef
Thursday, November 29, 2018, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Alessandro Tricoli
The determination of the partonic structure of the proton is a central component of the precision phenomenology program at the Large Hadron Collider (LHC). This internal structure of nucleons is quantified in the collinear QCD factorization framework by the Parton Distribution Functions (PDFs), which encode the probability of finding quarks and gluons inside the proton carrying a given amount of its momentum. PDFs cannot currently be computed from first principles, and therefore they need to be determined from experimental data from a variety of hard-scattering cross-sections in lepton-proton and proton-proton collisions. This program, known as the global QCD analysis, involves combining the most PDF-sensitive data and the highest precision QCD and electroweak calculations available within a statistically robust fitting methodology. In this talk I review our current understanding of the quark and gluon structure of the proton, which emphasis for the implications for precision LHC phenomenology and searches for new physics, but also exploring other aspects of the nucleon structure such as their impact on high-energy neutrino telescopes, the connection with lattice QCD calculations, and the onset of novel small-x dynamics beyond the collinear framework. Finally, I highlight the prospects for improving our understanding of the quark/gluon structure of the nucleon at the high-luminosity LHC era.
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Physics Colloquium
"Studying Quantum Matter on Near-Term Quantum Computers"
Presented by Brian Swingle, University of Maryland and Institute of Advanced Study
Tuesday, November 27, 2018, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Rob Pisarski
From the point of view of fundamental physics, one of the greatest promises of quantum information science is a new set of quantum computational tools for addressing previously intractable problems. However, at present we find ourselves in an age of embodied quantum information, where the substrate carrying the information cannot yet be abstracted away and effects of noise cannot be neglected. Nevertheless, I will argue that such noisy, intermediate size quantum devices may be useful for addressing open problems in quantum many-body physics, and potentially quantum field theory. Using two case studies, I will show how quantum information is informing our understanding of quantum matter and how near-term quantum computers might realistically help.
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Nuclear Theory / RIKEN
"Casimir effect in Yang-Mills theory"
Presented by Dimitra Karabali, Lehman College CUNY
Friday, November 16, 2018, 2 pm
CFNS Seminar Room 2-38Hosted by: Niklas Mueller
We consider the Casimir effect in a gauge-invariant Hamiltonian formulation of nonabelian gauge theories in $(2+1)$ dimensions. We compare our analytical results with recent lattice simulations.
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RIKEN Lunch Seminar
"Exclusive $\rho$ meson production in $eA$ collisions: collinear factorization and the CGC"
Presented by Renaud Boussarie, BNL
Thursday, November 15, 2018, 12 pm
Building 510, Room 2-160Hosted by: Yuta Kikuchi
We will focus on the theoretical description of exclusive ρ meson production in eA collisions, using a hybrid factorization scheme which involves Balitsky's shockwave description of the Color Glass Condensate in the t channel, and Distribution Amplitudes (DAs) in the s channel. We will first give a quick introduction to the shockwave framework and to collinear factorization up to twist 3 for DAs, then we will apply these framweworks to the production of a longitudinal meson at NLO accuracy, and to the production of a transverse meson at twist 3 accuracy. We will insist on the experimental applications, and on several theoretical questions raised by our results: the dilute BFKL limit at NLO for diffraction, and collinear factorization breaking at twist 3.
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Environmental & Climate Sciences Department Seminar
"Global models for atmospheric new particle formation from the CERN CLOUD experiment"
Presented by Hamish Gordon, Leeds
Thursday, November 15, 2018, 11 am
Conference Room Bldg 815EHosted by: Laura Fierce
In this seminar I will introduce the CERN CLOUD chamber experiment studying atmospheric new particle formation. I will then focus on work we have done to parameterize new particle formation and growth rates for atmospheric models. I will discuss the implementation of the parameterizations into the models, and the implications of the results from these models for estimated cloud condensation nuclei concentrations and indirect aerosol radiative forcing. The uncertainties in modelling new particle formation remain large, and I will outline how we are moving forward to try to reduce them.
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Physics Colloquium
"From nuts to soup: Recent advances in QCD in the Regge limit and the approach to thermalization in heavy-ion collisions"
Presented by Raju Venugopalan, BNL
Tuesday, November 13, 2018, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Rob Pisarski
Twenty five years to date, Larry McLerran and the speaker proposed that the Regge limit of QCD could be described by a many-body classical effective field theory now known as the Color Glass Condensate (CGC). Our radical conjecture was prompted by the phenomenon of gluon saturation, whereby many-body gluodynamics leads to the emergence of a semi-hard scale that screens color in the infrared. In the first part of this talk, we will review developments since in the CGC effective theory, and emphasize a paradigm shift in what constitutes fundamental degrees of freedom in the Regge limit. We shall also outline a color memory effect in the CGC which bears an exact analogy to the gravitational memory effect that could be discovered by LIGO in the near future. This correspondence in turn prompts one to speculate that asymptotic so-called BMS-like symmetries of gravity may also apply in QCD's Regge limit, leading to novel insight into how pions form "soft hair" on glue. In the second part of the talk, we discuss how the CGC provides an ab initio picture of thermalization and hydrodynamics in ultrarelativistic heavy-ion collisions. We focus on the discovery of a pre-thermal turbulent attractor, its topological properties, and a remarkable universality between this attractor and cold atomic gases prepared with the same boundary conditions.
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Nuclear Theory / RIKEN Seminar
"Towards laboratory detection of superfluid phases of QCD"
Presented by Ajit Srivastava, Institute of Physics, Bhubaneswar
Friday, November 9, 2018, 2 pm
CFNS Seminar Room 2-38Hosted by: Niklas Mueller
Exotic phases of QCD exhibiting strong correlations exist at very high baryon density and relatively low temperatures. Examples of such phases range from nucleon superfluid phases expected to occur in the interior of neutron stars, to possible color superconducting phases, which may occur in the core of a neutron stars. Some of these phases may also occur in relativistic heavy ion collisions in the high baryon density regime, e.g. at RHIC (BES), FAIR, and NICA. We discuss the possibilities of detecting them in heavy ion collisions focusing on the universal aspects of associated phase transitions.
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Particle Physics Seminar
"Managing scientific data at the exascale with Rucio"
Presented by Martin Barisits, CERN
Thursday, November 8, 2018, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Paul Laycock, Eric Lancon
Rucio is an open source software framework that provides scientific collaborations the functionality to organise, manage, and access their volumes of data. The data can be spread across heterogeneous data centres at widely distributed locations. Rucio has been originally developed to meet the requirements of the high-energy physics experiment ATLAS, and is continuously extended to support the LHC upgrades and more diverse scientific communities. Next to ATLAS, the Xenon1t dark matter search and AMS cosmic ray experiment are also using Rucio in production. The CMS experiment will deploy Rucio by 2019 and operate at a similar scale as ATLAS. Additionally several other experiments such as Belle-2 (B mesons), SKA (radio astronomy), LIGO (gravitational waves), DUNE and IceCube (both neutrino) are currently evaluating Rucio for adoption. This talk will discuss the exascale challenges these scientific experiments face and how Rucio will help to address them. Specifically the possibilities for uncomplicated deployment, easy integration in existing data workflows and the benefit of using the automated services provided by Rucio, will be shown. Also the transition of Rucio from a single-experiment system to an open community project, developed by scientists from multiple experiments, will be presented as well.
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Condensed-Matter Physics & Materials Science Seminar
"Dirac fermions and critical phenomena: exponents and emergent symmetries"
Presented by Michael Scherer, University of Cologne, Germany
Thursday, November 8, 2018, 1:30 pm
ISB Bldg. 734 Conf. Rm. 201 (upstairs)Hosted by: Laura Classen
Dirac fermions appear as quasi-particle excitations in various condensed-matter systems for example in graphene or as surface states of topological insulators. Close to a quantum phase transition they exhibit a series of exotic properties, e.g., emergent symmetries, fluctuation-induced critical points, the appearance of two length scales and a hierarchy of mass gaps. I discuss mechanisms that are behind these phenomena from a quantum field-theoretical point of view. Further, I present a four-loop renormalization group study for the determination of the Dirac fermions' critical behavior and compare to the predictions of complementary approaches such as quantum Monte Carlo and the conformal bootstrap. Finally, I will also comment on the possibility to test duality conjectures with these calculations.
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NSLS-II Friday Lunchtime Seminar
"Materials Tribology: An Application-Driven Field with Rich Opportunities for Fundamental Studies of Surface Chemistry, Physics, Structure"
Presented by Brandon A. Krick, Department of Mechanical Engineering and Mechanics, Lehigh University
Friday, November 2, 2018, 12 pm
NSLS-II Bldg. 743 Rm 156Hosted by: Ignace Jarrige
The significant economic (~3-6% of developed countries GDP) and environmental (several percent of our annual energy consumption) impacts of friction and wear make tribology is an important, application-driven field. However, there is an opportunity and need for inherently fundamental studies on surface chemistry, physics and structure to elucidate fundamental mechanisms for friction and wear. The non-equilibrium and transient nature of shear-induced changes caused by contacting surfaces in relative motion requires both in situ and ex situ advanced characterization techniques; many of these only available at the light source at Brookhaven. A brief overview of shear-induced (sliding friction/wear) alterations of surfaces will be presented for material systems including: - environmental and tribochemistry molybdenum disulphide based coatings for space applications - shear-induced band bending in GaN - mechanochemistry of polymer nanocomposites
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Particle Physics Seminar
"Search of the rare decay of KL→π0νν at J-PARC"
Presented by Yu-Chen, Tung
Thursday, November 1, 2018, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Chao Zhang
J-PARC KOTO is a dedicated experiment to search for the rare KL→π0νν decay. This decay is special not only because of its direct CP violating process, but also its theoretical cleanness. In the standard model, the branching ratio of KL→π0νν is calculated to be 3×10-11 with only a few percent uncertainty, which provides a clean base to explore new physics through finding deviations from the standard model. In the recently released results of data collected in 2015, the sensitivity of search was improved by an order of magnitude from the previous result and no event was observed in the signal region, with the prediction of 0.4 background event. In this talk, I will report the analysis and DAQ plan toward the sensitivity of O(-11).
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HET Seminar
"Unveiling New Physics Through Angular Distributions at the LHC"
Presented by Rodolfo Capdevilla, Notre Dame
Wednesday, October 31, 2018, 2:30 pm
Small Seminar Room, Bldg. 510Hosted by: Gopolang Mohlabeng
Angular distributions are commonly used in high precision measurements at colliders. In this talk, we will use the Collins-Soper angular distribution with two goals; to identify the quantum numbers of the mediators in a simplified dark matter model, and to enhance the signal to background ratio of resonance searches in W gamma production at the LHC with the use of the so called Radiation Amplitude Zero.
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Physics Colloquium
"Cosmic Chandlery with Thermonuclear Supernovae"
Presented by Alan Calder, Stony Brook University
Tuesday, October 30, 2018, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Rob Pisarski
Thermonuclear (Type Ia) supernovae are bright stellar explosions distinguished by light curves that can be calibrated to allow for their use as "standard candles" for measuring cosmological distances. Our research investigates how properties of the host galaxy such as composition and age influence properties of the progenitor system, which in turn influence the thermonuclear burning during an event and thus its brightness. I will present the results from ensembles of simulations addressing the influence of age and composition on the brightness of an event. These results show that the outcome depends sensitively on the nuclear burning, particularly weak interactions. Thus precise measurement of the largest possible scales of the Universe requires accurately capturing physics at some of the smallest scales.
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Particle Physics Seminar
"Preparing Physics Software for the Future - the HEP Software Community"
Presented by Benedikt Hegner, BNL
Thursday, October 25, 2018, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Alessandro Tricoli
Particle physics has an ambitious and broad experimental programme for the coming decades. This programme requires large investments in detector hardware, either to build new facilities and experiments, or to upgrade existing ones. Similarly, it requires commensurate investment in the R&D of software to acquire, manage, process, and analyse the shear amounts of data to be recorded. In planning for the High Luminosity LHC in particular, it is critical that all of the collaborating stakeholders agree on the software goals and priorities, and that the efforts complement each other. In this spirit, the High Energy Physics community created a white paper (arXiv:1712.06982) to describe and define the R&D activities required to prepare for this software upgrade. This presentation describes the expected software and computing challenges and the already taken steps to tackle them
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C-AD Accelerator Physics Seminar
"HL-LHC Crab Cavities and Recent Beam Tests in the SPS Machine"
Presented by Dr. Rama Calaga, CERN
Wednesday, October 24, 2018, 4 pm
Bldg. 911B, Second Floor, Large Conf. Rm., Rm. A2The design, development and challenges of the fabrication of the DQW crab cavity cryomodule is outlined. The successful installation and beam tests with protons in the SPS machine are presented along lessons learned and future plans for the HL-LHC series manufacturing.
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Nuclear Theory/RIKEN Seminar
"Studying out-of-equilibrium Quark-Gluon Plasma with QCD kinetic"
Presented by Aleksas Mazeliauskas, University of Heidelberg
Friday, October 19, 2018, 2 pm
Building 510, CFNS Seminar Room 2-38Hosted by: Niklas Mueller
In relativistic heavy nucleus collisions an ultra-dense, high-temperature state of nuclear matter is created with de-confined quarks and gluons. Understanding how the non-equilibrium Quark-Gluon Plasma thermalizes is important in connecting the initial state physics with the emergent hydrodynamic behavior of the QGP at later times. In this talk, I will use weakly coupled QCD kinetic theory with quark and gluon degrees of freedom to study the QGP evolution in the far-from-equilibrium regime, where it exhibits universal scaling, and its approach to thermal and chemical equilibrium.
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Particle Physics Seminar
"Stronger together: combining searches for new heavy resonances"
Presented by Viviana Cavaliere, Brookhaven National Lab
Thursday, October 18, 2018, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Alessandro Tricoli
Many theories beyond the Standard Model predict new s-channel resonances decaying into two bosons (WW,ZZ,WZ,WH,ZH) and possibly leptons (ll, lv). This talk will summarize the recent ATLAS combination of heavy resonances searches which places stringent constraints on the couplings to boson, quarks and leptons taking advantage of the statistical combination of searches in different channels. Prospect for future resonances searches at HL-LHC and HE-LHC will be discussed as well.
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HET Seminar
"Flavor Physics in Lattice QCD as a Window into BSM Physics: |Vcb| and the B -> D* l nu Semileptonic Decay"
Presented by Alejandro Vaquero, University of Utah
Wednesday, October 17, 2018, 2:30 pm
Small Seminar Room, Bldg. 510Hosted by: Aaron Meyer
Flavor physics provides a rich variety of phenomena that can be used to probe the SM without requiring the high energies present only in the largest particle accelerators. Among the quantities that could be employed to perform precision test of the SM, the CKM matrix elements takes up a prominent place. This lecture deals with the |V_{cb}| CKM matrix element, whose determinations through inclusive and exclusive decays currently display a 2\sigma discrepancy, and show how lattice QCD methods can reduce the uncertainty in the theoretical estimates and rule out (or not) the existence of unknown physics at play.
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Center for Functional Nanomaterials Seminar
"Probing nanostructured materials atom by atom: An ultra-high resolution aberration-corrected electron microscopy study"
Presented by Dr. Nasim Alem, Penn State University
Wednesday, October 17, 2018, 10 am
CFN, Bldg 735, Conference Room B, 2nd FloorHosted by: Chuck Black
Defects can have a profound effect on the macroscale physical, chemical, and electronic properties of nanostructures. They can lead to structural distortions, introduce extra states in the band gap and give rise to excess potential locally at buried interfaces. While defects and interfaces have been a well-studied subject for decades, little is known about their local atomic and chemical structure, sub-Angstrom structural distortions within their vicinity, and their stability and transition dynamics under extreme conditions. Using ultra-highresolution aberration-corrected S/TEM imaging and spectroscopy, this talk will discuss our recent efforts on the determination of the defect chemistry and sub-Angstrom relaxation effects in nanostructures around dopants, grain boundaries, domain walls, and interfaces in the family of 2D crystals, complex oxides, and diamond carbon nanothreads. In the family of 2D crystal transition metal dichalcogenides (TMDs) alloys, we show how the formation of chemically ordered states and vacancy/dopant coupling leads to unusual relaxation effects around dopant-vacancy complexes. In addition, we explore stability and transition dynamics of defects leading to grain boundary migration in monolayer TMDs under electron beam irradiation. This talk also presents how ferroelectric polarization emerges at the atomic level across the domain walls in single phase and hybrid complex oxide systems and the impact of this emergence on the macroscale properties. Finally, we uncover the atomic and chemical structure of the carbon nanothreads using low dose high resolution electron microscopy. Bio: Nasim Alem is an assistant professor in the Materials Science and Engineering department at the Penn State University. Nasim received her B.S. degree in Metallurgical Engineering from Sharif University of Technology, Tehran, Iran and her M.S. degree in Materials Science and Engineering from Worcester Polytechnic Institute. She received her PhD from the Ma
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Nuclear Physics Seminar
"Energy dependence of jet quenching signatures in heavy-ion collisions"
Presented by James Brandenburg
Tuesday, October 16, 2018, 11 am
Small Seminar Room, Bldg. 510Hosted by: Rongrong Ma
High-pT partons traveling through the quark-gluon plasma (QGP) lose energy due to strong interactions. This effect, called jet-quenching, is attributed to collisional and radiative energy losses as high-pT partons travel through and interact with the dense medium. Over the years jet-quenching has become well established in high-energy heavy-ion collisions. In high-energy A+A collisions, the observation of jet-quenching is considered to be clear evidence of QGP formation. The Beam Energy Scan program at RHIC provided a unique opportunity to study the QCD phase diagram and to search for the turn off of key QGP signatures, such as jet-quenching, at sufficiently low collision energies. The collision energy dependence of jet-quenching effects, quantified through the nuclear modification factor (Rcp) of charged and identified hadrons will be discussed. The limitations of Rcp as an observable will be discussed and compared with a more differential technique for quantifying jet-quenching. Finally, the outlook for improved jet-quenching measurements in the second phase of the RHIC Beam Energy Scan will be presented.
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Condensed-Matter Physics & Materials Science Seminar
"In-situ Investigation of Crystallization of a Metallic Glass by Bragg Coherent X-ray Diffraction"
Presented by Bo Chen, Tongji University, China
Monday, October 15, 2018, 11 am
ISB Bldg. 734, Conf. Rm. 201 (upstairs)Hosted by: Ian Robinson
The crystallization behaviour of metallic glass (MG) has long been investigated ever since the discovery of these important functional materials [1]. Compared with crystalline and amorphous extremes, mate-rials containing crystalline precipitates within an otherwise amorphous MG or partially crystallized ma-terials have distinct properties that could be a way of tuning the materials' characteristics. Several methods including powder X-ray diffraction (XRD), transmission electron microscope (TEM) and se-lected area electron diffraction (SAED) are usually combined to characterize the degree of crystalline structure in amorphous materials. Until now, these methods, however, have failed to show the crystal-lization of individual crystal grains in three dimensions. In this work, the in-situ Bragg coherent X-ray diffraction imaging (BCDI) [2, 3] reveals the grain growth and the strain variation of individual crystals up to the sizes of a few hundred nanometers from the pure Fe-based MG powder during heating. We have found that there is preferential growth along one direction during the crystal formation; there is fractal structure around the developing crystal surface; there is also strain relaxation within the growing crystals while cooling. The work supports a two-step crystallization model for the Fe-based MG during heating. This could help to pave the way for designing partially crystalline materials with their at-tendant soft magnetic, anti-corrosive and mechanical properties. References [1] D. H. Kim, W. T. Kim, E. S. Park, N. Mattern, and J. Eckert, Prog. Mater. Sci. 2013, 58, 1103. [2] M. A. Pfeifer, G. J. Williams, I. A. Vartanyants, R. Harder and I. K. Robinson, Nature 2006, 442, 63. [3] I. K. Robinson and R. Harder, Nat. Mater. 2009, 8, 291.
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Nuclear Theory/RBRC Seminar
"Anyonic particle-vortex statistics and the nature of dense quark matte"
Presented by Srimoyee Sen, University of Arizona
Friday, October 12, 2018, 2 pm
Building 510, Room 2-38Hosted by: Andrey Tarasov
We show that Z_3-valued particle-vortex braiding phases are present in high density quark matter. Certain mesonic and baryonic excitations, in the presence of a superfluid vortex, have orbital angular momentum quantized in units of 1/3. Such non-local topological features can distinguish phases whose realizations of global symmetries, as probed by local order parameters, are identical. If Z_3 braiding phases and angular momentum fractionalization are absent in lower density hadronic matter, as is widely expected, then the quark matter and hadronic matter regimes of dense QCD must be separated by at least one phase transition.
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NSLS-II Colloquium Series
"Biophysical Studies of an RNA Virus particle and its Maturation: Insights into an Elegantly Programmed Nano-machine"
Presented by John E. (Jack) Johnson, Department of Integrative Structural and Computational Biology, The Scripps Research Institute
Thursday, October 11, 2018, 4 pm
Large Seminar Room, Bldg. 510Hosted by: John Hill
Nudaurelia Capensis ? Virus (N?V) is a eukaryotic, quasi-equivalent, RNA virus, with a T=4 surface lattice, where maturation is dramatic (a change in particle size of 100Å) and is novel in that it can be investigated in vitro. Here we use X-ray crystallography, biochemistry, Small Angle X-ray Scattering, and electron cryo-microscopy and image reconstruction (CryoEM), to characterize maturation intermediates, an associated auto-catalytic cleavage, the kinetics of morphological change and to demonstrate that regions of N?V subunit folding are maturation-dependent and occur at rates determined by their quasi-equivalent position in the capsid. Matsui, T., Lander, G. C., Khayat, R., and Johnson, J. E. 2010. Subunits fold at position-dependent rates during maturation of a eukaryotic RNA virus. Proc Natl Acad Sci U S A 107:14111-5. Veesler, D., and Johnson, J.E. 2012. Virus Maturation. Annual review of biophysics 41:473-496. Doerschuk, P. C., Gong, Y., Xu, N., Domitrovic, T., and Johnson, J. E. 2016. Virus particle dynamics derived from CryoEM studies. Curr Opin Virol 18:57-63.
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Particle Physics Seminar
"Higgs to beauty quarks"
Presented by Caterina Vernieri, SLAC
Thursday, October 11, 2018, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Alessandro Tricoli
The Higgs boson discovery at the LHC marked a historic milestone in the study of fundamental particles and their interactions. Over the last six years, we have begun measuring its properties, which are essential to build a deep understanding of the Higgs sector of the Standard Model and to potentially uncover new phenomena. The Higgs' favored decay mode to beauty (b) quarks (~60%) had so far remained elusive because of the overwhelming background of b-quark production due to strong interactions. Observing the Higgs decay to b-quarks was one of the critical missing pieces of our knowledge of the Higgs sector. Measuring this decay is a fundamental step to confirm the mass generation for fermions and may also provide hints of physics beyond the Standard Model. The CMS observation of the decay of the SM Higgs boson into a pair of b-quarks exploiting an exclusive production mode (VH) is yet another major milestone. This experimental achievement at the LHC, considered nearly impossible in the past, makes use of several advanced machine learning techniques to identify the b-quark distinctive signature, improve the Higgs boson mass resolution, and discriminate the Higgs boson signal from background processes.
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NSLS-II Friday Seminar
"Highly Active and Stable Carbon Nanosheets Supported Iron Oxide for Fischer-Tropsch to Olefins Synthesis"
Presented by Congjun Wang, National Energy Technology Laboratory, Pittsburgh, PA
Friday, October 5, 2018, 12 pm
NSLS-II Bldg. 743 Rm 156Hosted by: Ignace Jarrige
Light olefins production utilizes the energy intensive process of steam cracking. Fischer-Tropsch to olefins (FTO) synthesis potentially offers a more sustainable alternative. Here we show a promising FTO catalyst comprised of iron oxide nanoparticles supported on carbon nanosheets (CNS) fabricated from the carbonization of potassium citrate, which incorporates well dispersed K-promoter throughout the CNS support. This catalyst exhibits, to the best of our knowledge, the highest iron time yield of 1790–1990 μmolCO/gFe•s reported in the literature, 41% light olefins selectivity, and over 100 hours stable activity, making it one of the best performing FTO catalysts. Detailed characterization, including synchrotron X-ray spectroscopy, illustrates that the CNS support facilitates iron oxide reduction to metallic iron, leading to efficient transformation to the active iron carbide phase during FTO reaction. Since K is a commonly used promoter, our K-promoted CNS support potentially has broad utility beyond the FTO reactions demonstrated in the current study.
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Particle Physics Seminar
"SB/BNL Joint Cosmo seminar: Weighing Galaxy Clusters with Weak Lensing in Hyper Suprime-Cam Survey"
Presented by Dr. Elinor Medezinski, Princeton University
Thursday, October 4, 2018, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Chi-Ting Chang
The most fundamental question in observational cosmology today is what is the nature of dark energy and dark matter. Clusters of galaxies serve as beacons to the growth of structure over cosmic scales, making them a sensitive cosmological tool. However, accurately measuring their masses has been notoriously difficult. Weak lensing provides the best direct probe of the cluster mass, both the baryonic and dark components, but it requires high-quality wide-field imaging and careful control of systematics. With its unprecedentedly deep and exquisite seeing, the Subaru Hyper Suprime-Cam (HSC) survey is an ongoing campaign to observe 1,400 square degrees to r~26, providing the closest precursor to LSST. In this talk, I will present our new field-leading results from the first HSC data release of ~150 square degrees that encompass thousands of clusters. Harnessing our new HSC survey, I measure benchmark weak lensing cluster masses with improved methodology, and reconcile previous tension on cosmological parameters between the SZ and CMB within the Planck survey. In the next decade, LSST and WFIRST will discover hundreds of thousands of galaxy clusters, peering deep to the epoch of formation. I will describe these surveys and the multifold breakthrough science we will achieve in the new era of astronomy.
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Special Particle Physics Seminar
"Latest XENON1T results"
Presented by Qing Lin, Columbia University
Thursday, October 4, 2018, 1 pm
Small Seminar Room, Bldg. 510Hosted by: Chao Zhang
Understanding the properties of dark matter particle is a fundamental problem in particle physics and cosmology. The search of dark matter particle scattering off nuclei target using ultra-low background detector is one of the most promising technology to decipher the nature of dark matter. The XENON1T experiment, which is a dual phase detector with ~2.0 tons of xenon running at the Gran Sasso Laboratory in Italy, is designed to lead the field of dark matter direct detection. Since November 2016, the XENON1T detector is continuously taking data, with a background rate of more than one order of magnitude lower than any current generation dark matter search experiment. In this talk, I will present the latest results from XENON1T. Details about the XENON1T detector as well as the data analysis techniques will also be covered.
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Nuclear Physics Seminar
"Exploring the Phase Diagram with Succeptibility Scaling Functions: Epic Voyage or Just Another Bad Trip"
Presented by Roy A Lacey, Stony Brook University
Tuesday, October 2, 2018, 11 am
Small Seminar Room, Bldg. 510Hosted by: Jiangyong Jia
A major goal of the ongoing experimental programs at RHIC is to chart the QCD phase diagram.Pinpointing the location of the first order phase boundary which terminates at a critical end point (CEP), in the temperature versus baryon chemical potential (T,µB) plane of this phase diagram, is key to this mapping. Finite-Size-Finite-Time succeptibility scaling functions can give crucial insight on these essential landmarks of the phase diagram. I will discuss recent attempts to extract and use such scaling functions to pin down the location of the CEP, as well as the associated critical exponents required to identify its universality class.
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Particle Physics Seminar
"(Somewhat) New ideas in ultralight DM searches:"
Presented by Babette Döbrich, CERN
Monday, October 1, 2018, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Alessandro Tricoli
The search for ultra-light Dark Matter particles complements the search for more ``classical'' Dark Matter candidates at the GeV scale in an important fashion. I will review the motivation of the QCD axion, highlighting ongoing established techniques and set-ups and explain in detail a novel technique based on microwave filters (RADES), ongoing at CERN. Finally I will present results of one of the possibly cheapest experiments for ultralight Dark Photon Dark Matter (FUNK) achieving competitive results.
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Nuclear Theory/RIKEN Seminar
"Neutrinoless double beta decay in effective field theory"
Presented by Jordy De Vries, UMass Amherst
Friday, September 28, 2018, 2 pm
Building 510, CFNS Seminar Room 2-38Hosted by: Chun Shen
Next-generation neutrinoless double-beta decay experiments aim to discover lepton-number violation in order to shed light on the nature of neutrino masses. A non-zero signal would have profound implications by demonstrating the existence of elementary Majorana particles and possibly pointing towards a solution of matter-antimatter asymmetry in the universe. However, the interpretation of the experimental signal (or lack thereof) requires care. First of all, a single nonzero measurement would indicate lepton-number violation but will not identify the underlying source. Second, complicated hadronic and nuclear input is required to connect the experimental data to a fundamental description of lepton-number violation. In this talk, I will use effective field theories to connect neutrinoless double-beta decay measurements to the fundamental lepton-number-violating source.
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Particle Physics Seminar
"Measurements of the branching fraction and time-dependent CP asymmetries for B0 -> J/psi pi0 decays"
Presented by Bilas Pal, BNL
Thursday, September 27, 2018, 3 pm
Small Seminar Room, Bldg. 510Hosted by: David Jaffe
Measurements of the time-dependent CP asymmetries and branching fraction of B0 -> J/psi pi0 will be discussed. The CP asymmetry parameters for the decay B0 -> J/psi pi0 have previously been measured by BaBar and Belle experiments, but the results of mixing induced CP asymmetry (S) were not in good agreement with each other. Furthermore, the BaBar result lies outside the physically allowed region. Previous Belle measurements were based on 535M BB-bar pairs. We updated the measurements using the final Belle data set of 772M BB-bar pairs.
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Condensed-Matter Physics & Materials Science Seminar
"Universality and quantum criticality of the one-dimensional spinor Bose gas"
Thursday, September 27, 2018, 1:30 pm
ISB Bldg. 734 Conf. Rm. 201Hosted by: Igor Zaliznyak
We investigate the universal thermodynamics of the two-component one-dimensional Bose gas with contact interactions in the vicinity of the quantum critical point separating the vacuum and the ferromagnetic liquid regime. We find that the quantum critical region belongs to the universality class of the spin-degenerate impenetrable particle gas which, surprisingly, is very different from the single-component case and identify its boundaries with the peaks of the specific heat. In addition, we show that the compressibility Wilson ratio, which quantifies the relative strength of thermal and quantum fluctuations, serves as a good discriminator of the quantum regimes near the quantum crit- ical point. Remarkably, in the Tonks-Girardeau regime the universal contact develops a pronounced minimum, reflected in a counterintuitive narrowing of the momentum distribution as we increase the temperature. This momentum reconstruction, also present at low and intermediate momenta, signals the transition from the ferromagnetic to the spin-incoherent Luttinger liquid phase and can be detected in current experiments with ultracold atomic gases in optical lattices.
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Sustainable Energy Technologies Department
"Advances in Ultra-High Energy Resolution STEM-EELS"
Presented by Tracy C. Lovejoy, Nion R&D
Wednesday, September 26, 2018, 2 pm
Bldg. 734, Room 201Hosted by: Feng Wang
The capabilities of scanning transmission electron microscopes (STEMs) have advanced very significantly in the last two decades. The first major advance was the successful implementation of electron-optical aberration correction, which allowed the STEMs to reach direct sub-angstrom resolution in 2002 [1]. This improvement made the imaging and spectroscopy of single atoms straightforward. A very recent major development has been the improvement of energy resolution of EELS due to the introduction of a new generation of monochromators and ultra-stable electron spectrometers. The Ultra-High Energy Resolution Monochromated EELS-STEM (U-HERMES™) system developed by Nion combines a dispersing-undispersing ground-potential monochromator [2], a bright cold-field-emission gun, an advanced aberration corrector, and a new EEL spectrometer. The latest version of the system allows 5 meV energy resolution EELS and has achieved 1.07 Å spatial resolution at the sample at 30kV when monochromating, and it greatly extends the capabilities of vibrational spectroscopy in the EM, introduced 4 years ago [3]. U-HERMES™ has so far been used for: damage-free identification of different bonds including hydrogen bonds in guanine [4]; probing atomic vibrations at surfaces and edges of nano-objects with nm-level spatial resolution [5]; achieving sub-nm spatial resolution in images obtained with dark-field EELS vibrational signals [6]; nanoscale mapping of phonon dispersion curves [7]; nanoscale temperature determination by electron energy gain spectroscopy [8]; identification of different isotopes by vibrational spectroscopy in the EM [9]; vibrational spectroscopy of ice; and vibrational fingerprinting of biological molecules.
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Physics Colloquium
"Unraveling the nucleon's mass and spin structure at an Electron-Ion Collider"
Presented by Yoshitaka Hatta, BNL and Kyoto University
Tuesday, September 25, 2018, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Rob Pisarski
The US-based Electron-Ion Collider (EIC) is a future high-luminosity, polarized collider dedicated to the physics of the nucleon/nucleus structure. Among the many physics problems that can be addressed at the EIC, I will focus on the origin of the mass and spin of the nucleon, namely, how they can be understood in terms of quarks' and gluons' degrees of freedom. I will give a review of the mass and spin decompositions in QCD and discuss possible experimental observables.
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Particle Physics Seminar
"Searches for decays of a Higgs boson into pairs of light (pseudo)scalars with the ATLAS detector"
Presented by Ljiljana Morvaj
Tuesday, September 25, 2018, 10:30 am
Small Seminar Room, Bldg. 510Hosted by: Alessandro Tricoli
The branching ratio of the Standard Model (SM) Higgs boson to non-SM or "exotic" states is currently constrained to be less than 34% at 95% confidence level. This opens possibility to search for new particles in the decays of the Higgs boson. Such searches could provide a unique access to hidden-sector states that are singlets under the SM gauge transformations. A search for decays of the Higgs boson to a pair of new spin–0 particles, H → aa, where the a–bosons decay to a b-quark pair and a muon pair, is presented in this seminar. The analysis uses 36.1 fb−1 of proton-proton collisions data with √s = 13 TeV recorded by the ATLAS experiment at the LHC in 2015 and 2016. No deviation from the Standard Model prediction is observed and limits on Br(H → aa → bbμμ) are set in the a–boson mass range of 20–60 GeV. Searches in other final states, such as four b-quarks (H → aa → 4b) and two jets and two photons (H → aa → ggγγ), are also discussed.
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Nuclear Theory/RIKEN Seminar
"Status of Pythia 8 for an Electron-Ion Collider"
Presented by Ilkka Helenius, University of Tubingen
Friday, September 21, 2018, 2 pm
Building 510, CFNS Seminar Room 2-38Hosted by: Andrey Tarasov
Pythia 8 is a general-purpose Monte-Carlo event generator widely used to simulate high-energy proton-proton collisions at the LHC. Recently it has been extended to handle also other collision systems involving lepton and heavy-ion beams. In this seminar I will review the current Pythia 8 capabilities in processes relevant to an Electron-Ion Collider (EIC) and discuss about the projected future improvements. The relevant processes can be divided into two regions based on the virtuality of the intermediate photon: deeply inelastic scattering (DIS) at high virtualities and photoproduction at low virtualities. I will begin with an introduction of the event generation steps in Pythia 8 and then briefly discuss how the DIS processes can be simulated. Then I present our photoproduction framework and compare the results to the HERA data for charged-hadron and dijet production in lepton-proton collisions. In particular I discuss about the role of multiparton interactions in photon-proton interactions with resolved photons and how these can be constrained with the existing HERA data. Then I discuss how the same framework can be applied to ultra-peripheral heavy-ion collisions at the LHC where one can study high-energy photon-nucleus interactions in a kinematic region comparable to EIC. Finally I will show our first predictions for dijet production in these events and quantify the contribution of diffractive events according to the hard diffractionmodel that has been recently implemented into Pythia 8.
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Particle Physics Seminar
"The Belle II Experiment"
Presented by Bryan Fulsom, PNNL
Thursday, September 20, 2018, 3 pm
Small Seminar Room, Bldg. 510Hosted by: David Jaffe
The first generation of B-Factories, BaBar and Belle, operated over the previous decade and produced many world-leading measurements related to flavor physics. Their discoveries contributed to the awarding of the 2008 Nobel Prize in Physics. The Belle II experiment, now underway at the KEK laboratory in Japan, is a substantial upgrade of both the Belle detector and the KEKB accelerator. It aims to collect 50 times more data than existing B-Factory samples. This will provide unprecedented sensitivity to new physics signatures in the flavor sector. This talk will present the upgrade efforts of the Belle II experiment, results from its recent first e+e- collisions, and the future physics opportunities the experiment will provide.
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Condensed-Matter Physics & Materials Science Seminar
"Multiloop functional renormalization group: Exact flow equations from the self-consistent parquet relations"
Presented by Fabian Kugler, Ludwig-Maximilians-Universitat Munchen, Germany
Thursday, September 20, 2018, 1:30 pm
ISB 734 Conference Room 201Hosted by: Andreas Weichselbaum
The functional renormalization group (fRG) is a versatile, quantum-field-theoretical formulation of the powerful RG idea and has seen a large number of successful applications. The main limitation of this framework is the truncation of the hierarchy of flow equations, where typically effective three-particle interactions are neglected altogether. From another perspective, the parquet formalism consists of self-consistent many-body relations on the one- and two-particle level and allows for the most elaborate diagrammatic resummations. Here, we unify these approaches by deriving multiloop fRG flow equations from the self-consistent parquet relations [1]. On the one hand, this circumvents the reliance on higher-point vertices within fRG and equips the method with quantitative predictive power [2]. On the other hand, it enables solutions of the parquet equations in previously unaccessible regimes. Using the X-ray-edge singularity as an example, we introduce the formalism and illustrate our findings with numerical results [3]. Finally, we discuss applications to the 2D Hubbard model [4] and the combination of multiloop fRG with the dynamical mean-field theory. [1] F. B. Kugler and J. von Delft, arXiv:1807.02898 (2018) [2] F. B. Kugler and J. von Delft, PRB 97, 035162 (2018) [3] F. B. Kugler and J. von Delft, PRL 120, 057403 (2018) [4] A. Tagliavini, C. Hille, F. B. Kugler, S. Andergassen, A. Toschi, and C. Honerkamp, arXiv:1807:02697 (2018)
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Physics Colloquium
"Potential and Issues for Future Accelerators and Ultimate"
Presented by Stephen Brooks, BNL
Tuesday, September 18, 2018, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Andrei Nomerotski
Particle colliders have been remarkably successful tools in particle and nuclear physics. What are the future trends and limitations of accelerators as they currently exist, and are there possible alternative approaches? What would the ultimate collider look like? This talk examines some challenges and possible solutions. Accelerating a single particle rather than a thermal distribution may allow exploration of more controlled interactions without background. Also, cost drivers are possibly the most important limiting factor for large accelerators in the foreseeable future so emerging technologies to reduce cost are highlighted.
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Special Particle Physics Seminar
"Flavor physics and CP violation - Recent results from combined BaBar+Belle measurements, ongoing work at LHCb, and prospects for the new physics searches at Belle II"
Presented by Markus Roehrken, CERN
Monday, September 17, 2018, 1 pm
Small Seminar Room, Bldg. 510Hosted by: David Jaffe
During the 2000s, the BaBar experiment at SLAC (Stanford/USA) and the Belle experiment at KEK (Tsukuba/Japan) performed a very successful flavor physics program. BaBar and Belle discovered CP violation in the B meson system and put tight experimental constraints on the quark-flavor sector of the Standard Model. The excellent experimental confirmation of the theory predictions by BaBar and Belle led to the Nobel Prize in physics for Makoto Kobayashi and Toshihide Maskawa in 2008. Continuing on these efforts, the new high-luminosity accelerator SuperKEKB and the next-generation B factory experiment Belle II recently started operation at KEK in Japan. SuperKEKB is designed to operate at an instantaneous luminosity of 8x10^35/cm^2/s, which is a factor 40 higher than the world record achieved by its predecessor KEKB. The upgraded Belle II detector will collect data samples about two orders of magnitudes larger than those of the BaBar and Belle experiments. In this talk, we introduce to flavor physics and CP violation. We will present recent results of a combined analysis campaign, which for the first time makes simultaneous use of the large final data samples of BaBar and Belle in single physics analyses. The approach provides access to an integrated luminosity of about 1.1 inverse attobarn, and thus allows to perform early Belle II-like measurements. In addition, ongoing work of the speaker at LHCb is reported. At the end of the talk, the prospects for the new physics searches in heavy flavor decays governed by quantum-loop effects at Belle II are briefly discussed.
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Particle Physics Seminar
"Probing the Higgs Yukawa couplings at the LHC"
Presented by Konstantinos Nikolopoulos
Thursday, September 13, 2018, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Alessandro Tricoli
The Higgs boson observation by ATLAS and CMS Collaborations at the CERN Large Hadron Collider has completed the Standard Model; the culmination of a century of discoveries. Despite the overwhelming success of the Standard Model to-date, the origin of fermion masses through Yukawa couplings to the Higgs doublet is loosely constrained experimentally and offers opportunities for BSM physics contributions. The status of the determination of the Higgs boson Yukawa couplings at the LHC will be presented and the prospects for the future will be discussed.
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Joint BNL/RIKEN HET Seminar
"Higgs pair production via gluon fusion at NLO QCD"
Presented by Julien Baglio, Tuebingen U.
Wednesday, September 12, 2018, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Sally Dawson
Since the discovery of a Higgs boson in 2012 at CERN, accessing its properties is one of the main goals of the Large Hadron Collider (LHC) experimental collaborations. The triple Higgs coupling in particular is a primary target as it would be a direct probe of the shape of the scalar potential at the origin of the electroweak-symmetry-breaking mechanism, and is directly accessed via the production of a pair of Higgs bosons. In this view, it is of utmost importance to reach high precision in the theoretical prediction of Higgs boson pair production cross section at the LHC. I will present in this talk the calculation of the 2-loop QCD corrections to the Higgs-pair-production cross section via gluon fusion, that is the main production mechanism, including the top-quark mass effects in the loops. It will be shown that they can be significant in the Higgs-pair-mass differential distributions.
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Nuclear Theory/RBRC Seminar
"Temperature, Mass, Flavor: Emerging Phase Structure of SU(3) Gauge Theories with Fundamental Quarks"
Presented by Ivan Horvath, University of Kentucky
Friday, September 7, 2018, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Rob Pisarski
Recently we have outlined the general phase structure of the above relevant theory set, inferred from probing the glue by external Dirac probes. Its novelty and simplicity stems from the conclusion that changes in temperature, mass and number of flavors lead to analogous dynamical effects. In this talk I will review that picture, and introduce an important refinement of it that is currently emerging in the thermal corner of the phase diagram.
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Condensed-Matter Physics & Materials Science Seminar
"Pair-breaking quantum phase transition in superconducting nanowires"
Presented by Andrey Rogachev, University of Utah
Friday, September 7, 2018, 11 am
ISB Bldg. 734 Conference Room 201 (upstairs)Hosted by: Ivan Bozovic
Quantum phase transitions (QPT) between distinct ground states of matter are widespread phenomena, yet there are only a few experimentally accessible systems where the microscopic mechanism of the transition can be tested and understood. In this talk we will report on discovery that a magnetic-field driven quantum phase transition in MoGe superconducting nanowires can be fully explained by the critical theory of pair-breaking transitions characterized by a correlation length exponent v≈1 and dynamic critical exponent z≈ 2. We find that in the quantum critical regime, the electrical conductivity is in agreement with a theoretically predicted scaling function and, moreover, that the theory quantitatively describes the dependence of conductivity on the critical temperature, field magnitude and orientation, nanowire cross-sectional area, and microscopic parameters of the nanowire material. At the critical field, the conductivity follows a T^(d–2)/z dependence predicted by phenomenological scaling theories and more recently obtained within a holographic framework. Our work uncovers the microscopic processes governing the transition: the pair-breaking effect of the magnetic field on interacting Cooper pairs overdamped by their coupling to electronic degrees of freedom. It also reveals the universal character of continuous quantum phase transitions. In the talk we will also briefly comment on reliability of the finite-size scaling analysis, origin of zero-bias anomaly in wires and implication of our finding for QPT in superconducting films.
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RIKEN/NT & Quantum Computing Seminar
"Quantum Uncertainty and Quantum Computation"
Presented by Ivan Horvath, University of Kentucky
Thursday, September 6, 2018, 12:30 pm
Building 510, Room 2-160Hosted by: Rob Pisarski
I will discuss the uncertainty in quantum mechanics as a property reflecting the "quantity" (measure) on the set of possible probing outcomes. This is in contrast to the commonly used "spectral distance" (metric). An unexpected insight into the nature of quantum uncertainty (and that of measure) is obtained as a result. One of the motivations for considering measure uncertainty is that it is directly relevant for assessing the efficiency of quantum computation.
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Nuclear Physics Seminar
"Neutron production and capture in stellar nucleosynthesis:^{22}Ne(\Alpha,n)^{25}Mg reaction and radiative neutron captures of radioactive nuclei"
Presented by Shuya Ota, Texas A&M University
Tuesday, September 4, 2018, 11 am
Small Seminar Room, Bldg. 510Hosted by: Jin Huang
Most of elements heavier than Fe in the Universe are produced by a series of neutron capture reaction and ??-decay in stars. The s-process, which occurs under moderate neutron environments (~107-10 neutrons/cm3) such as in He burning of massive stars, is responsible for producing almost half of the heavy elements. Neutrons for the s-process environment is believed to be supplied by two dominant reactions, one of which is 22Ne(?,n)25Mg reaction. This reaction in massive stars is dominated by a few resonance reactions. Nevertheless, there remain large uncertainties about contribution of the reaction to the s-process nucleosynthesis because the reaction cross sections are too small for direct measurements due to Coulomb barrier (E? = 400-900 keV in the lab system). In the first half of this seminar, I will present our experiment to determine these resonance strengths with a cyclotron accelerator at Texas A&M University. The experiment was performed by an indirect approach using 6Li(22Ne,25Mg+n)d ?-transfer reaction, in which resonance properties such as neutron decay branching ratios of produced 26Mg were studied by measuring deuterons, ?-ray, and 26Mg in coincidence using large arrays of Si and Ge, and a magnetic spectrometer. Our results showed neutron production from 22Ne(?,n)25Mg reaction can be about 10 times lower than past measurements. The effect of our measurements on the s-process nucleosynthesis will be discussed. In the second half of this seminar, I will present our experiments to determine neutron capture cross sections of radioactive nuclei using the Surrogate Reaction method [1]. Neutron capture reactions for the s-process involve relatively long-lived nuclei neighboring stability in the nuclear chart. Therefore, the Surrogate Reaction, which creates the same compound nuclei as the neutron capture reaction using a stable beam and target, can be a useful approach. On the other hand, the r- process, which produces the other half
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Special Nuclear Theory/RIKEN Lunch Seminar
"Signal-to-noise issues in non-relativistic quantum matter: from entanglement to thermodynamics"
Presented by Joaquin Drut, University of North Carolina
Thursday, August 30, 2018, 12:30 pm
Building 510, Room 2-160Hosted by: Rob Pisarski
Non-relativistic quantum matter, as realized in ultracold atomic gases, continues to be a remarkably versatile playground for many-body physics. Experimentalists have exquisite control over temperature, density, coupling, and shape of the trapping potential. Additionally, a wide range of properties can be measured: from simple ones like equations of state to more involved ones like the bulk viscosity and entanglement. The latter has received much attention due to its connection to quantum phase transitions, but it has proven extremely difficult to compute: stochastic methods display exponential signal-to-noise issues of a very similar nature as those due to the infamous sign problem affecting finite-density QCD. In this talk, I will present an algorithm that solves the signal-to-noise issue for entanglement, and I will show results for strongly interacting systems in three spatial dimensions that are the first of their kind. I will also present a few recent explorations of the thermodynamics of polarized matter and other cases that usually have a sign problem, using complexified stochastic quantization.
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Nuclear Physics Seminar
"Probe strong magnetic field in QGP with dielectrons from photon-photon interactions"
Presented by Zhangbu Xu, BNL
Tuesday, August 28, 2018, 11 am
Small Seminar Room, Bldg. 510Hosted by: Rongrong Ma
We presents first measurements of $e^+e^-$ pair production from light-light scattering in non-central heavy ion collisions. The excess yields peak distinctly at low transverse momentum with sqrt() between 40 to 60 MeV/c. The excess yields can be explained only when the photon-photon interactions are included in model calculations. However, the measured pT^2 distributions are significantly broader than model calculation and are different between Au+Au and U+U. Our measurements provide a possible experimental evidence of the existence of strong electromagnetic field. And I will discuss its possible impact on emerging phenomena in hadronic heavy-ion collisions, such as Chiral Magnetic Effect.
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Condensed-Matter Physics & Materials Science Seminar
"Spinon Confinement and a Longitudinal Mode in One Dimensional Yb2Pt2Pb"
Presented by Bill Gannon, Department of Physics and Astronomy, Texas A&M University
Thursday, August 23, 2018, 1:30 pm
ISB Bldg. 734 Conf. Rm. 201 (upstairs)Hosted by: Alexei Tsvelik
Abstract: The Yb3+ magnetic moments in Yb2Pt2Pb are seemingly classical, since the large spin-orbit coupling of the 4f-electrons and the crystal electric field dictate a J = +/-7/2 Yb ground state doublet. Surprisingly, the fundamental low energy magnetic excitations in Yb2Pt2Pb are spinons on one dimensional chains, shown to be in good agreement with the behavior expected with the XXZ Hamiltonian for nearly isotropic, S = +/-1/2 magnetic moments. We have performed new high resolution neutron scattering measurements to examine the properties of these excitations in a magnetic field. In fields larger than 0.5 T, the chemical potential closes the gap to the spinon dispersion, modifying the quantum continuum through the formation of a spinon Fermi surface. This leads to the formation of spinon bound states along the chains, coupled to a longitudinally polarized interchain mode at energies below the quantum continuum. The ground state doublet nature of the Yb ions ensures that at all fields, transverse excitations are virtually nonexistent, allowing direct measurement of the mode dispersion.
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RIKEN Lunch Seminar
"Universality in Classical and Quantum Chaos"
Presented by Masanori Hanada, YITP
Thursday, August 16, 2018, 12:30 pm
Building 510, Room 2-160Hosted by: Enrico Rinaldi
We study the chaotic nature of classical and quantum systems. In particular, we will study the detail of the Lyapunov growth. We will show the evidence that the spectrum of Lyapunov exponents admits universal description by Random Matrix Theory, and systems dual to black holes exhibit 'strong' universality.
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Condensed-Matter Physics & Materials Science Seminar
"Advances in high energy electron holography"
Presented by Dr. Toshiaki Tanigaki, Hitachi, Japan
Friday, August 10, 2018, 1:30 pm
Conference room in building 480Hosted by: MG Han
Advances in High-Voltage Electron Holography T. Tanigaki Research & Development Group, Hitachi, Ltd. Email: toshiaki.tanigaki.mv@hitachi.com Electron holography can observe electromagnetic field inside materials and devices at high-resolution around atomic scale. The high penetration power of a high energy electron wave is crucial to observing magnetic structures, which exist only in thick samples. It is particularly crucial in three-dimensional (3D) observations, which require a series of sample observations with the sample increasingly tilted so that the projected sample thickness increases with the tilt angle. As an example of this, magnetic vortex cores confined in stacked ferromagnetic (Fe) discs were observed three-dimensionally by using vector-field electron tomography with a 1.0 MV holography electron microscope [1]. To invent new functional materials and devices for establishing a sustainable society, methods for controlling atomic arrangements in small areas such as interfaces have become important [2,3]. Electron holography is a powerful tool for analyzing the origins of functions by observing electromagnetic fields and strains at high resolutions. The advantages of high-voltage electron holography are high resolution and penetration power due to high energy electron waves. The quest for finding the ultimate resolution through continuous improvements on holography electron microscopes led to the development of an aberration corrected 1.2 MV holography electron microscope [4,5] (Figure 1). We describe recent results obtained by using the high-voltage electron holography. Spatial resolution of 1.2 MV holography electron microscope reached 0.043 nm at high-resolutions, when the sample was placed in a high magnetic field of the objective lens [4]. Under the observation conditions, in which the sample was placed in a field-free position for observing a magnetic field, the spatial res
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Special Particle Physics Seminar
"Deep Neural Network Techniques R&D for Data Reconstruction of Liquid Argon TPC Detectors"
Presented by Kazuhiro Terao, SLAC National Accelerator Laboratory
Tuesday, August 7, 2018, 10 am
Small Seminar Room, Bldg. 510Hosted by: Chao Zhang
Liquid Argon Time Projection Chambers (LArTPCs) are capable of recording images of charged particle tracks with breathtaking resolution. Such detailed information will allow LArTPCs to perform accurate particle identification and calorimetry, making it the detector of choice for many current and future neutrino experiments. However, analyzing such images can be challenging, requiring the development of many algorithms to identify and assemble features of the events in order to reconstruct neutrino interactions. In the recent years, we have been investigating a new approach using deep neural networks (DNNs), a modern solution to a pattern recognition for image-like data in the field of Computer Vision. A modern DNN can be applied for various types of problems such as data reconstruction tasks including interaction vertex finding, pixel clustering, and particle/topology type identification. We have developed a small inter-experiment collaboration to share generic software tools and algorithms development effort that can be applied to non-LArTPC imaging detectors. In this talk I will discuss the challenges of LArTPC data reconstruction, recent work and future plans for developing a full LArTPC data reconstruction chain using DNNs.
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Particle Physics Seminar
"Significant Excess of Electron-Like Events in the MiniBooNE Short-Baseline Neutrino Experiment"
Presented by William Louis, Los Alamos National Lab
Thursday, August 2, 2018, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Chao Zhang
The MiniBooNE experiment at Fermilab observes a total electron-neutrino event excess in both neutrino and antineutrino running modes of 460.5 +- 95.8 events (4.8 sigma) in the energy range from 200-1250 MeV. The MiniBooNE L/E distribution and the allowed region from a two-neutrino oscillation fit to the data are consistent with the L/E distribution and allowed region reported by the LSND experiment. All of the major backgrounds are constrained by in-situ event measurements, so non-oscillation explanations would need to invoke new anomalous background processes. Although the data are fit with a two-neutrino oscillation model, other models may provide better fits to the data. The MiniBooNE event excess will be further studied by the Fermilab short-baseline neutrino (SBN) program.
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Condensed-Matter Physics & Materials Science Seminar
"Imaging Non-equilibrium Dynamics in Two-Dimensional Materials"
Presented by Kenneth Beyerlein, Max Planck Institute for the Structure and Dynamics of Matter, Germany
Wednesday, August 1, 2018, 11 am
ISB Bldg. 734, Conf. Rm. 201 (upstairs)Hosted by: Ian Robinson
The interfaces in thin film heterostructures dictate the performance of an electronic device. Understanding their behavior upon exposure to light is important for advancing photovoltaics and spintronics. However, producing an atomic image of these dynamics is an under-determined problem without a unique solution. In this talk, I will show how a set of ultrafast soft X-ray diffraction rocking curves can be spliced together to add constraints to the phase retrieval problem. In doing so, the anti-ferromagnetic order through a NdNiO3 film after illumination of the substrate with a mid-Infrared laser pulse will be imaged. Notably, a disordered phase front initiated at the substrate interface is shown to evolve at twice the speed of sound. This time-spliced imaging technique opens a new window into the correlated dynamics of two-dimensional materials.
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Special Particle Physics Seminar
"Dark Matter Annual Modulation with SABRE"
Presented by Lindsey Bignell, Australian National University
Tuesday, July 31, 2018, 1:30 pm
Small Seminar Room, Bldg. 510Hosted by: David Jaffe
SABRE is a dark matter direct detection experiment with a target of ultra-pure NaI(Tl). Our experiment is motivated by the DAMA result; a long-standing and highly statistically significant modulation of the count rate in their NaI(Tl) detector that is consistent with that expected from the dark matter halo. However, a number of other direct detection experiments, using different target materials, exclude the dark matter parameter space implied by DAMA for the simplest WIMP-nucleus interaction models. SABRE hopes to carry out the first model-independent test of the DAMA claim, with sufficient sensitivity to confirm or refute their result. SABRE will also operate identical detectors in the northern and southern hemisphere, to rule out seasonally-modulated backgrounds. The southern detector will be housed at the first deep underground laboratory in the Southern Hemisphere: the Stawell Underground Physics Laboratory. This talk will give an overview of the SABRE design and its predicted sensitivity, as well as an update on the proof-of-principle detector which will be operating this summer.
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Sambamurti Lecture
"Capturing the Inner Beauty of the Quark Gluon Plasma"
Presented by Jin Huang, Brookhaven National Laboratory
Friday, July 27, 2018, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: John Haggerty
The Quark Gluon Plasma (QGP) filled the universe in the first microsecond after the Big Bang and today is routinely recreated in high energy nuclear collisions at RHIC and the LHC. While experiments have revealed an array of surprising QGP properties, such as perfect fluidity, extreme vorticity, and near total opaqueness to hard scattered quarks and gluons, the detailed physics that gives rise to these properties remains a focus of forefront research. Heavy quarks, particularly the very heavy beauty quark, provide the means to clarify the connection between the microscopic physics of the QGP and its larger scale properties. Beauty quarks – or b-quarks – are produced rarely in collisions at RHIC, and the planned sPHENIX experiment will be equipped with a high rate vertex tracker enabling precision measurements of b-quark observables, such as B-meson suppression and flow, the differential suppression of Upsilon states and a number of observables related to b-quark jets. These b-quark probes will provide crucial information about the microscopic description of QGP at RHIC energies. In this talk, I will explain b-quark physics in the QGP, current measurements, the program at the planned sPHENIX experiment and its relevance to the future Electron Ion Collider.
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Nuclear Theory/RIKEN Seminar
"Jets as a probe of transverse spin physics"
Presented by Zhongbo Kang, UCLA
Friday, July 27, 2018, 2 pm
Building 510, CFNS Seminar Room 2-38Hosted by: Chun Shen
Jets are collimated spray of hadrons that are naturally produced in high energy colliders. They are powerful probes of many different aspects of QCD dynamics. In this talk, we will demonstrate how to use jets to explore the transverse momentum dependent (TMD) physics. A novel TMD framework to deal with back-to-back two particle correlations is presented, with which we could study the Sivers asymmetry for photon+jet or dijet production in transversely polarized proton-proton collisions. At the end of the talk, we also show how jet substructure could be used to explore the TMD fragmentation functions. We expect these studies to have important applications at RHIC in the future.
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Nuclear Theory Seminar
"Medium Modification of Jet Substructure in the Opacity Expansion"
Presented by Matthew Sievert, Los Alamos
Friday, July 27, 2018, 11 am
Building 510, CFNS Seminar Room 2-38Hosted by: Yacine Mehtar-Tani
The modification of jets and their substructure in the presence of quark-gluon matter, beyond solely the quenching of their production, is a cornerstone of jet tomography. Although the nature of different nuclear environments can vary widely, the manner in which an external potential leads to a modification of jets and their substructure is universal and applies to both hot and cold nuclear matter. An order-by-order calculation of the medium modifications is possible on the basis of the opacity expansion, a series which can be truncated at finite order if the average number of scatterings in the quark-gluon matter is not too large. Other methods exist which can resum the full opacity series into a path integral formalism that remains applicable at very high opacities. In this talk, I will present a new calculation in the opacity expansion approach which computes the gluon substructure of a quark jet with exact kinematics at second order in opacity. I will also derive a set of recursion relations which can be used to construct higher orders terms in the opacity expansion to any finite order. And finally, I will compare this approach to the resumed path integral formalism, discussing the strengths and weaknesses of both methods and opportunities to study their overlap.
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Condensed-Matter Physics & Materials Science Seminar
"Atomic level structural characterization of materials by electron microscopy"
Presented by Shize Yang, Center for Functional Nanomaterials
Thursday, July 26, 2018, 4 pm
Bldg. 480, Conference RoomHosted by: Yimei Zhu
In recent years, with the development of technologies, electron microscopy techniques have been widely developed. Important advancement has been achieved on in-situ electron microscopy, cryogenic electron microscopy, electron tomography, advanced electron energy loss spectroscopy etc. In this talk I will briefly introduce and show how those techniques provide a vital role in the structural characterization of 2D materials, catalysts and battery materials.
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Nuclear Theory Seminar
"Jet fragmentation in a QCD plasma: Universal quark/gluon ratio and wave turbulence"
Presented by Soeren Schlichting, University of Washington
Thursday, July 26, 2018, 11 am
Building 510, CFNS Seminar Room 2-38Hosted by: Yacine Mehtar-Tani
We investigate the radiative break-up of a highly energetic quark or gluon in a high-temperature QCD plasma. Within an inertial range of momenta T
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Environmental & Climate Sciences Department Seminar
"Invariant and insensitive: climate model microphysics as a scaling problem"
Presented by Mikael Witte, National Center for Atmospheric Research
Thursday, July 19, 2018, 11 am
Conference Room Bldg 815EHosted by: Yangang Liu
Clouds are inherently multiscale phenomena: the particles that make up clouds are typically microns to millimeters, while the large-scale circulations that drive cloud systems can be hundreds of kilometers across. Limited computational power and the need to accurately represent the large-scale circulations in numerical simulations of the atmosphere make explicit inclusion of cloud microphysics a practical impossibility. In the last 20 years there has been a shift toward representing microphysics as scale-aware processes. Despite this shift, many unanswered questions remain regarding the scaling characteristics of microphysical fields and how best to incorporate that information into parameterizations. In this talk, I will present results from analysis of high frequency in situ aircraft measurements of marine stratocumulus taken over the southeastern Pacific Ocean aboard the NCAR/NSF C-130 during VOCALS-REx. First, I will show that cloud and rain water have distinct scaling properties, indicating that there is a statistically and potentially physically significant difference in the spatial structure of the two fields. Covariance of cloud and rain is a strong function of length/grid scale and this information can easily be incorporated in large-scale model parameterizations. Next I will show results from multifractal analysis of cloud and rain water to understand the spatial structure of these fields, the results of which provide a framework for development of a scale-insensitive microphysics parameterization. Finally, I compare observed microphysical scaling properties with those inferred from large eddy simulations of drizzling stratocumulus, applying the same analyses as applied to the aircraft observations. We find that simulated cloud water agrees well with the observations but the drizzle field is substantially smoother than observed, which has implications for the ability of limited-area models to adequately reproduce the spatial structure o
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Condensed-Matter Physics & Materials Science Seminar
"Mechanism of strange metal and strange metal state near a heavy fermion quantum critical point"
Presented by Chung-Hou Chung, Department of Electrophysics, National Chiao-Tung University, Taiwan
Wednesday, July 18, 2018, 1:30 pm
ISB Bldg. 734 Conference Room 201Hosted by: Alexei Tsvelik
Strange metal (SM) behaviors with non-Fermi liquid (NFL) properties, generic features of heavy fermion systems near quantum phase transitions, are yet to be understood microscopically. A paradigmatic example is the magnetic field-tuned quantum critical heavy fermion metal YbRh2Si2 (YRS), revealing a possible SM state over a finite range of fields at low temperatures when substituted with Ge. Above a critical field, the SM state gives way to a heavy Fermi liquid with Kondo correlation. The NFL behavior shows most notably a linear-in-temperature electrical resistivity and a logarithmic-in-temperature followed by a power-law-in-temperature in the specific heat coefficient at low temperatures [1]. We propose a mechanism to explain it: a quasi-2d fluctuating anti-ferromagnetic short-range resonating-valence-bond (RVB) spin-liquid competing with the Kondo correlation (Fig. 1) [2]. Applying renormalization group analysis on an effective field theory beyond a large-N approach to an antiferromagnetic Kondo-Heisenberg model, we identify the critical point, and explain remarkably well the SM behavior. Our theory goes beyond the well-established framework of quantum phase transitions and serves as a new basis to address open issues of the non-Fermi liquid behavior in quantum critical heavy-fermion compounds, such as: the strange superconductivity observed in the "115" family CeMIn5 (M=Co, Rh)[3]. References: [1] J. Custers et al., Nature 424, 524 (2003); J. Custers et al., Phys. Rev. Lett. 104, 186402 (2010). [2] Yung-Yeh Chang, Silke Paschen, and Chung-Hou Chung, Phys. Rev. B 97, 035156 (2018). [3] Y. Y. Chang,, F. Hsu, S. Kirchner, C. Y. Mou, T. K. Lee and C. H. Chung (un-published).
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C-AD Accelerator Physics Seminar
"Coherent THz Radiation from Plasma Oscillation Driven by Laser Pulses"
Presented by Dr. Min Sup Hur, Physics Department - UNIST Korea
Tuesday, July 17, 2018, 4 pm
Bldg. 911B, 2nd floor - Large Conference RoomHosted by: Dr. Bingping Xiao
Plasma, a gas of electric charges, exhibits a fundamental oscillating behavior, the plasma oscillation. Similar to the classical harmonic oscillator, but charged, the plasma oscillation is potentially an outstanding source of coherent, monochromatic radiation with high intensity and high frequency. However, harnessing the plasma oscillation and taking the radiation out of it are never trivial problems. In this presentation, I introduce one novel method to generate an isolated plasma dipole oscillation by colliding laser pulses in a plasma, eventually to obtain a quasi-narrowband, powerful THz emission. The conceptual connection of the idea to the astrophysical plasma emission is also addressed.
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Nuclear Theory/RIKEN Seminar
"Confronting hydrodynamic predictions with Xe-Xe heavy-ion collision data"
Presented by Matt Luzum, Univeristy of Sao Paulo
Friday, July 13, 2018, 2 pm
Building 510, CFNS Seminar Room 2-38Hosted by: Chun Shen
Comparing collision systems of different size, at near the same collision energy, offers us the opportunity to probe the scaling behavior and therefore the nature of the system itself. Recently, we made predictions for Xe-Xe collisions at 5.44 TeV using viscous hydrodynamic simulations, noting that the scaling from the larger Pb-Pb system is rather generic, and arguing that robust predictions can be made that do not depend on details of the model. Here we confront our predictions with measurements that were subsequently made in a short Xe-Xe run at the LHC by the ALICE, ATLAS, and CMS collaborations. We find that the predictions are largely confirmed, with small discrepancies that could point the way to a better understanding of the medium created in such collisions.
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RIKEN Lunch Seminar
"Topological structures in finite temperature QCD"
Presented by Rasmus Larsen, BNL
Thursday, July 12, 2018, 12:30 pm
Building 510, Room 2-160Hosted by: Yuya Tanizaki
We report our study on the properties of the topological structures present in the QCD medium. We use dynamical domain wall fermion configurations on lattices of size 32^3x8 and detect the topological structures through the zero modes of the overlap operator. We explicitly show that the properties of the zero modes of the QCD Dirac operator agrees well with that of calorons with non-trivial holonomy. Different profiles of the zero modes are observed, ranging from solutions that are localized in all four spacetime dimensions, to profiles that are localized in the spatial directions, and constant along the temporal extent of the lattice. This indicates towards the presence of instanton-dyons in the hot QCD medium around Tc, where the distance between dyons control the shape and extent of the zero modes.
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Condensed-Matter Physics & Materials Science Seminar
"Electron-microscopy-guided designing of ferroelectric materials for nonvolatile memories and multifunctional nanodevices"
Presented by Linze Li, University of California @ Irvine
Thursday, July 12, 2018, 11 am
Bldg. 480, Conference RoomHosted by: Yimei Zhu
As a prototypical example of functional oxides, ferroelectric materials have been utilized in a broad range of electronic, optical, and electromechanical applications and hold the promise for the design of future high-density nonvolatile memories and multifunctional nanodevices. The utilities of ferroelectrics are derived from the structures and switching of ferroelectric domains, or from their coupling to other material functionalities. In recent years, advanced imaging techniques based on aberration-corrected scanning transmission electron microscopy (STEM) and in situ transmission electron microscopy (TEM) have become powerful methods to characterize ferroelectric oxides, allowing nanoscale polarization states to be unambiguously determined with sub-Angstrom resolution, and allowing domain switching processes to be directly resolved in real time. In this presentation I will show several examples of applying advanced STEM or TEM-based techniques to the study of the static and dynamic properties of domains and domain walls in ferroelectric and multiferroic BiFeO3 thin films. Atomic structures and electrical switching behaviors of charged domain walls have been observed. A strong interaction between the ferroelectric polarization and nanoscale impurity defects has been discovered, and a new route to the production of exotic polarization states by utilizing such interaction has been proposed and established. These findings open up the possibility for the designing of novel ferroelectric materials and multifunctional devices with nanoscale structural defects or charged domain walls as essential components.
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Joint Nuclear Physics and High Energy Physics Seminar
"Parity-Violating and Parity-Conserving Asymmetries in ep and eN Scattering in the Qweak Experiment"
Presented by Wouter Deconinck, College of William & Mary
Tuesday, July 10, 2018, 11 am
Small Seminar Room, Bldg. 510Hosted by: Jin Huang
The Standard Model provides the current best description of fundamental particles and forces, but among other limitations it fails to account for dark matter which could manifest itself as more massive particles. Precision measurements of well predicted observables in the Standard Model allow for highly targeted tests for physics beyond the Standard Model. The Qweak experiment at Jefferson Lab has made the first precise determination of the weak charge of the proton in elastic scattering of longitudinally polarized electrons from unpolarized protons. To achieve the required precision to measure the small parity-violating asymmetry of -226.5 ± 9.3 parts per billion, we directed a high current polarized electron beam on a liquid hydrogen target and integrated scattered events in eight azimuthally symmetric fused silica Cerenkov detectors. We find a value for the weak charge of proton of 0.0719 ± 0.0045, in agreement with predictions of the Standard Model. This result rules out leptoquark masses below 2.3 TeV and excludes generic new semi-leptonic parity-violation physics beyond the Standard Model below 3.5 TeV. To correct for the contributions from background processes, we conducted several additional parity-violating and parity-conserving asymmetry measurements with different kinematics (elastic and through the production of a Delta resonance), polarization (longitudinal and transverse), and targets (protons, electrons, aluminum, and carbon). I will discuss the results of the main experiment and highlight several ancillary results of interest to experiments at future facilities.
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Condensed-Matter Physics & Materials Science Seminar
"Room-temperature magnetic spiral order induced by disorder"
Presented by Christopher Mudry, Paul Scherrer Institut, Switzerland
Monday, July 2, 2018, 1:30 pm
ISB Bldg. 734 Conf. Rm. 201 (upstairs)Hosted by: Alexei Tsvelik
Upon cooling, the compound YBaCuFeO5 undergoes a phase transition to an antiferromagnetic long-range ordered phase. Upon further cooling, a second phase transition to a magnetic spiral phase takes place. The latter transition temperature depends on the sample preparation and can reach room temperature. We propose a mechanism to explain the transition to a magnetic spiral ordered phase due to frustrating magnetic interactions that are introduced randomly along a single crystallographic direction as caused by a particular type of chemical disorder. This mechanism could open the way to high-temperature multiferroism.
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NSLS-II Friday Lunchtime Series
"Investigating slow kinetic processes using synchrotron radiation: A case study of cement hydration in nuclear waste cements"
Presented by Claire L. Corkhill, University of Sheffield, United Kingdom
Friday, June 29, 2018, 12 pm
NSLS-II Bldg. 743 Room 156Hosted by: M. Abeykoon, S. Chodankar, B. Ocko, J. Thieme, G. Wang
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Particle Physics Seminar
"First results from PROSPECT: The Precision Reactor Oscillation & Spectrum experiment"
Presented by David Jaffe, BNL
Thursday, June 28, 2018, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Chao Zhang
PROSPECT is a short-baseline reactor antineutrino experiment designed to search for eV-scale sterile neutrino oscillations and measure the 235U antineutrino energy spectrum from the High Flux Isotope Reactor at Oak Ridge National Laboratory. Deployed in early 2018, the 4ton, segmented, 6Li-loaded liquid scintillator detector began commissioning in March of this year. The detector consists of 154 segments that span a baseline of 7-9m from the compact highly enriched uranium core, enabling coverage of a wide range of oscillation parameter space. Full-scale prototypes have demonstrated excellent energy resolution and pulse-shape discrimination that will reject cosmogenic backgrounds and produce an unparalleled measurement of the 235U antineutrino spectrum. The first results of PROSPECT on sterile neutrino oscillations will be presented.
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Condensed-Matter Physics & Materials Science Seminar
"Imaging of Local Structure and Dynamics in Hard and Soft Condensed Matter Systems"
Presented by Dmitry Karpov, New Mexico State University
Friday, June 22, 2018, 1:30 pm
ISB Bldg. 734, Conf. Rm. 201 (upstairs)Hosted by: Ian Robinson
With advancement of coherent probes there is a shift from integral studies to highly localized studies in either spatial or temporal domains. Nanostructures and low dimensional phenomena, correlated fluctuations and associated transitions directly benefit from new instrumental capabilities. Studies of ferroelectric and magnetic materials and of their local behavior allow both to test fundamental physics concepts and provide access to technologies with direct practical applications. Topological phase transitions and topological defects are among the topics that are actively pursued in modern materials science. In recent study [1] conducted by our group we were able to visualize three-dimensional topological vortex structure in a volume of individual ferroelectric nanoparticle of barium titanate under external electric field using Bragg coherent diffractive imaging technique. Among other things we observed: (i) electric field induced structural transition from mixture of tetragonal and monoclinic phases to dominant monoclinic phase; (ii) controllable switching of vortex chirality; (iii) vortex mediated behavior of the nano-domains in the particle; (iv) and that the core of the vortex in the volume behaves as a nanorod of zero ferroelectric polarization which can be rotated by external electric field and can serve as a conducting channel for charge carriers. These findings can be used in the design of novel nanoelectronics devices and for creating artificial states of matter. Better understanding of the materials behavior at the nanoscale requires ways of probing anisotropies of the refractive index. Using polarized laser light, we've developed a method [2] termed birefringent coherent diffractive imaging that allows to extract projections of dielectric permittivity tensor in nematic liquid crystal. Further expanding this tool into full-vectorial mode shows that the method can be applied for imaging of magnetic domains, cellular structures, and ot
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Condensed-Matter Physics & Materials Science Seminar
"Theories of transport scaling in disordered semimetals and topological spin-nematic excitonic insulators in graphite under high magnetic field"
Presented by Ryuichi Shindo, Peking University, China
Thursday, June 21, 2018, 1:30 pm
ISB Bldg. 734 Conf. Rm. 201 (upstairs)Hosted by: Alexei Tsvelik
In the first part of my talk, I will talk about transport scaling theories in disordered Weyl semimetal [1,2]. In electronic band structure of solid state material, two band touching points with linear dispersion (called as `Weyl node') appear in pair in the momentum space. When they annihilate with each other, the system undergoes a quantum phase transition from Weyl semimetal (WSM) phase to a band insulator (BI) phase. The continuous phase transition is recently discovered in solid state materials [3]. The phase transition is described by a critical theory with a `magnetic dipole' like object in the momentum space. The critical theory hosts a disorder-driven quantum multicritical point, which is encompassed by three quantum phases, WSM phase, BI phase, and diffusive metal (DM) phase. Based on the renormalization group argument, we clarify transport scaling properties around the Weyl node at the quantum multicritical point as well as all phase boundaries among these three phases [1,2]. In the second part of my talk, I will argue that three-dimensional topological excitonic insulator is realized in graphite under high magnetic field [4,5]. Graphite under high magnetic field exhibits consecutive metal-insulator (MI) transitions as well as re-entrant insulator-metal (IM) transition at low temperature. We explain these enigmatic insulator phases as manifestation of excitonic insulator phases with spin nematic orderings ("SNEI" phases). Especially, we explain unusual field-dependences of in-plane resistivity in the graphite experiment by surface transports via 2+1 massless surface Dirac fermion in one of the SNEI phases [4,5]. [1] https://arxiv.org/abs/1803.09051, under review [2] https://arxiv.org/abs/1710.00572, selected as PRB editors' suggestion [3] Tian Liang, et.al., Science Advances, 3, e1602510 (2017) [4] https://arxiv.org/abs/1802.10253, under review [5] in preparation &
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Condensed-Matter Physics & Materials Science Seminar
"Fermi-Surface Reconstruction in Nd-doped CeCoIn5"
Presented by Elizabeth Green, Dresden High Magnetic Field Laboratory
Thursday, June 21, 2018, 11 am
ISB Bldg. 734 Seminar Room 201 (upstairs)Hosted by: Cedomir Petrovic
Heavy fermion compounds are well known to exhibit novel properties when exposed to high magnetic fields. Most notably CeCoIn5 exhibits a field-induced superconducting state at high magnetic fields known as the Qphase. Recent neutron scattering measurements show a similar Q-vector for the 5% Nd-doped CeCoIn5 at zero applied magnetic field [1] which has initiated intense theoretical and experimental work on this doping series. In this talk I will present de Haas-van Alphen effect measurements which indicate a drastic Fermi-surface reconstruction occurs between 2 and 5% Nd-doping levels. The cylindrical Fermi surface, believed to play a crucial role in superconductivity in these materials, develops a quasi-three-dimensional topology with increased doping levels thus reducing the likelihood of an enhanced nesting scenario, previously given as a possible explanation for the Q-phase. However, effective masses remain relatively unchanged up to 10% Nd indicating the crossing of a spin density wave type of quantum critical point. In addition, I will present evidence that by substituting Ce with Nd the electronic pairing potential may be altered. These results help elucidate the reasoning for the emergence of the Q-phase seen in the 5% Nd sample and may be relevant to other heavy fermion compounds. [1] S. Raymond et al., JPSJ 83, 013707 (2014).
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Physics Colloquium
"Subatomic Swirls and Massive Magnetic Fields - Lambda Polarization in Heavy Ion Collisions at RHIC"
Presented by Michael Lisa, Ohio State University
Tuesday, June 19, 2018, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Peter Petreczky
Last year, the STAR Collaboration at RHIC published the first observation of global hyperon polarization in heavy ion collisions. This polarization may be used to extract rotational substructure of the flow field. The result represented a striking validation of the near-equilibrium hydrodynamic paradigm and established the quark-gluon plasma at RHIC as by far the most vortical fluid in nature. More recent studies quantify the vortical structure systematics to challenge hydro models in detail. In addition to the rotational fluid substructure, hyperon polarization should probe the strong magnetic fields expected in heavy ion collisions. Measuring these fields is crucial for establishing and quantifying the so-called Chiral Magnetic Effect at RHIC. Experimental uncertainties are currently too large to conclusively measure the magnetic field, but detector upgrades at STAR and dedicated running at RHIC may allow a breakthrough in this year's (2018) run.
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Condensed-Matter Physics & Materials Science Seminar
"X-ray Scattering as a Tool for Understanding Nanostructured Materials"
Presented by Robert Koch, Alfred University
Tuesday, June 19, 2018, 1:30 pm
ISB Bldg. 734, Conf. Rm. 201 (upstairs)Hosted by: Ian Robinson
Materials with significant local distortions from the bulk average structure often show novel and useful properties. Identifying and quantifying the nature and extent of this correlated disorder1 is however quite challenging, as traditional crystallography and the associated tools often do not adequately describe such nanostructured materials. This is a manifestation of the "nanostructure problem"2 and the solution requires complex modelling incorporating multiple techniques. This talk focuses on the application of X-ray scattering and complex modelling as tools for understanding various nanostructured materials, including nanocrystalline nickel with large clusters of planar defects, interlayered non-silicon photovoltaics, geometrically frustrated ternary alkaline earth hexaborides, manganese dioxide nanosheet assemblies, and nanostructured noble metal alloys. Complex modelling leveraging both standard techniques as well as genetic algorithms, Markov chain Monte Carlo, and machine learning together provide synergistic understanding spanning length scales from a few Ångstrom to hundreds of nanometers. Additionally, an example of how complex modelling can be used to shed understanding on the nature of crystallographic disorder in superconducting alloys of 2H-TaSe2−xSx is discussed. A potential model is proposed whereby alloys of 2H-TaSe2−xSx are composed of interlayered sheets with two unique c-axes. This model is consistent with the observed 00l Bragg profile broadening trend and may help explain the suppression of charge density waves and maximization of superconductivity in these systems. 1. Keen, D. A. & Goodwin, A. L. The crystallography of correlated disorder. Nature 521, 303–309 (2015). 2. Billinge, S. J. L. & Levin, I. The problem with determining atomic structure at the nanoscale. Science 316, 561–565 (2007).
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Nuclear Physics Seminar
"Measurements of charm, bottom, and Drell-Yan via dimuons in p+p and p+Au collisions at sNN=200 GeV with PHENIX at RHIC"
Presented by Yue Hang Leung, Stonybrook University
Tuesday, June 19, 2018, 11 am
Small Seminar Room, Bldg. 510Hosted by: Jin Huang
Dilepton spectra are a classic probe to study ultra-relativistic heavy ion collisions. At RHIC energies, the dimuon continuum is dominated by correlated pairs from charm and bottom semi-leptonic decays and the Drell-Yan process. In this talk, we present measurements of µµ pairs from charm, bottom, and Drell-Yan in p+p and p+Au collisions at sNN = 200 GeV. Differential yields from charm and bottom in p+p collisions will be presented and implications for the relative contributions from different heavy flavor production mechanisms will be discussed. We will also present results of bottom yields in p+Au collisions and discuss the implications on cold nuclear matter effects. This study also enables first measurements of the Drell-Yan cross-section at s_{NN} = 200 GeV. Studying Drell-Yan production in p+Au collisions is a clean probe for modifications of the initial state. The Drell-Yan differential cross-sections in p+p collisions and progress on p+Au collisions will be presented.
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Particle Physics Seminar
"Jet substructure in ATLAS at the LHC – a tool for discoveries and measurements"
Presented by Peter Loch, University of Arizona
Thursday, June 14, 2018, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Alessandro Tricoli
The ATLAS experiment at the Large Hadron Collider (LHC) applies jet substructure analysis techniques to extract the internal energy flow in high energy jets produced in the proton-proton collisions in searches for new physics as well as in Standard Model (SM) measurements. In this talk we will introduce the most commonly applied techniques and present an overview of results from the respective performance evaluations. In addition, we will discuss selected configurations of tagging algorithms designed to extract two- or three-prong energy flow patterns inside a jet, as generated by decays of SM particles like the W-boson or the top quark, or possible new heavy particles indicating physics beyond the SM. A brief presentation of recent results from searches and SM measurements, including the recent measurement of the internal structure of light quark and gluon jets, concludes the talk.
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Condensed-Matter Physics & Materials Science Seminar
"Doublon-holon origin of the subpeaks at the Hubbard band edges"
Presented by Seung-Sup Lee, Ludwig-Maximilians-University, Germany
Thursday, June 14, 2018, 1:30 pm
ISB Bldg. 734 Conf. Rm. 201 (upstairs)Hosted by: Andreas Weichselbaum
Dynamical mean-field theory (DMFT) studies frequently observe a fine structure in the local spectral function of the SU(2) Fermi-Hubbard model (i.e., one-band Hubbard model) at half filling: In the metallic phase close to the Mott transition, subpeaks emerge at the inner edges of the Hubbard bands. Here we demonstrate that these subpeaks originate from the low-energy effective interaction of doublon-holon pairs, by investigating how the correlation functions of doublon and holon operators contribute to the subpeaks [1, 2]. We use the numerical renormalization group (NRG) as a DMFT impurity solver to obtain the correlation functions on the real-frequency axis with improved spectral resolution [3]. A mean-field analysis of the low-energy effective Hamiltonian [2] provides results consistent with the numerical result. The subpeaks are associated with a distinctive dispersion that is different from those for quasiparticles and the Hubbard bands. Also, the subpeaks become more pronounced in the SU(N) Hubbard models for larger number N of particle flavors, due to the increased degeneracy of doublon-holon pair excitations. Hence we expect that the sub-peaks can be observed in the photoemission spectroscopy experiments of multi-band materials or in the ultracold atom simulation of the SU(N) Hubbard models. [1] S.-S. B. Lee, J. von Delft, and A. Weichselbaum, Phys. Rev. Lett. 119, 236402 (2017). [2] S.-S. B. Lee, J. von Delft, and A. Weichselbaum, Phys. Rev. B 96, 245106 (2017). [3] S.-S. B. Lee and A. Weichselbaum, Phys. Rev. B 94, 235127 (2016).
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Condensed-Matter Physics & Materials Science Seminar
"Defects and their functional properties in multiferroic hexagonal systems"
Presented by Shaobo Cheng, McMaster University Canada
Monday, June 11, 2018, 2:30 pm
Bldg. 480, Conference RoomHosted by: Yimei Zhu
As a main component of quantum materials, multiferroic materials, which simultaneously have multiple orderings, hold promise for use in the next generation of memory devices. Taking advantage of the state-of-the-art transmission electron microscopy techniques, we have systematically studied the defects induced emergent phenomena in multiferroic hexagonal systems. Two single phase multiferroic hexagonal systems will be covered in this talk: YMnO3 and LuFe2O4. YMnO3 is a classic single phase multiferroic material with geometric ferroelectricity. The effects oxygen vacancies, partial edge dislocations, and interfacial atomic reconstructions will be presented. LuFe2O4 is a well-known multiferroic system with charge ordering origin. The effects of twins and interstitial oxygen in LuFe2O4 single crystalline sample will be discussed. The structural-property relationship for both systems has been tried to be established in our studies. Our findings demonstrate the structural flexibility of both manganites and ferrites, and open the door to new tunable multifunctional applications.
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Physics Colloquium
"How we got the government we have, and why scientists should engage with it"
Presented by Benn Tannenbaum, Sandia National Laboratory
Tuesday, June 5, 2018, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Andrei Nomerotski
It seems like a terrible time to be a scientist in the United States. Federal budgets aren't being passed, and when they are, funding for science never seems to increase. The debate over immigration reform—including what to do about visas for high-skilled workers, such as scientists—is stalled. Everyone agrees that cybersecurity is a problem, but no one seems to have a solution. Meanwhile, we have no meaningful debate in Congress or in the administration on climate change or energy policy. This lecture will cover how we got here, why we are stuck, some speculation on how the current administration is impacting research, and how the scientific community can impact policy.
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Nuclear Theory/RIKEN Seminar
"Liouville action, high multiplicity tail and shape of proton"
Presented by Vladimir Skokov, BNL
Friday, June 1, 2018, 2 pm
CFNS Seminar Room, 2-38Hosted by: Chun Shen
In this talk I violate the common wisdom "one seminar — one message" and discuss two seemingly unrelated results in the framework of the dilute-dense CGC approach: the effect of spatial eccentricity of the projectile (proton) shape on the second harmonic in double-inclusive gluon production and the theoretical description of the high gluon multiplicity tail. I will show that these two superficially unrelated results in combination may lead to unexpected consequences for the phenomenology of p-A collisions.
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Joint Nuclear Theory/RIKEN/CFNS Seminar
"Novel QCD Physics at an Electron-Ion Collider"
Presented by Stanley Brodsky, SLAC National Accelerator Laboratory, Stanford University
Friday, May 25, 2018, 10:30 am
Building 510, CFNS Seminar Room 2-38Hosted by: Chun Shen
An electron-ion collider can test many fundamental features of QCD for hadron and nuclear physics, including flavor-dependent antishadowing in deep inelastic electron-nucleus scattering, the breakdown of sum rules for nuclear structure functions, the role of ``hidden-color " degrees of freedom, and the effects of "color transparency" on the baryon-to-meson anomaly observed at high transverse momentum in heavy-ion collisions. I will also discuss intrinsic heavy quark phenomena and the production of exotic multiquark states at the EIC. On the theory side, I will discuss the new insights into color confinement that one obtains from light-front holography, including supersymmetric features of the meson, baryon, and tetraquark spectroscopy. The Principle of Maximum Conformality (PMC) can be used to systematically eliminate renormalization scale ambiguities and thus obtain scheme-independent pQCD predictions.
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Particle Physics Seminar
"K+ to pi+ nu nubar- First result from NA62 experiment"
Presented by Bob Velghe, TRIUMF
Thursday, May 24, 2018, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Chao Zhang
The K+ to pi+ nu nubar decay has been attracting interest for many decades. The accurate measurement of its branching ratio is a powerful test of the Standard Model (SM) and could reveal effects beyond the SM. As the decay occurs at the level of 1 in a 10 billion kaon disintegration, many experimental challenges have to be overcome. The CERN NA62 experiment uses a novel kaon decay-in-flight technique to observe K+ to pi+ nu nubar. The analysis of the 2016 data set was used to establish the method by allowing us to reach the 10^-10 single event sensitivity. The preliminary NA62 result on K+ to pi+ nu nubar from the analysis of the full 2016 data set will be presented.
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Condensed-Matter Physics & Materials Science Seminar
"Developing theoretical understanding of non-equilibrium phenomena"
Presented by Alexander Kemper, North Carolina State University
Thursday, May 24, 2018, 1:30 pm
ISB Bldg. 734 Conf. Rm. 201 (upstairs)Hosted by: Peter D. Johnson
In this talk, I will present an overview of some of our recent results in the area of non-equilibrium many-body theory. Experimental developments are enabling the study of electrons and atoms in the time domain with ever increasing resolution. The theoretical development has been somewhat lacking, and remains mostly rooted in extensions of equilibrium models. Our work has been to put the theoretical modeling on a firmer footing. Through numerical solution of the equations of motion, we can directly evaluate experimentally relevant spectra. These may be analyzed with the benefit of knowing the precise model and correlation functions that underlie the spectra. Most of the talk will focus on the interaction between a system of electrons interacting with several degrees of freedom, including the lattice, impurity scattering, and each other. Typically, non-equilibrium results are analyzed through a framework that relies on equilibrium intuition. Our results show that the validity of this type of analysis falls on a spectrum that varies from correct to wholly incorrect, which I will illustrate with specific examples. This line of thinking will be further developed by considering the flow of energy between various subsystems.
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Particle Physics Seminar
"CERN openlab R&D for the LHC Run3 and Run4"
Presented by Maria Girone, CERN
Tuesday, May 22, 2018, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Sergey Panitkin
LHC Run3 and Run4 represent an unprecedented challenge for HEP computing in terms of both data volume and complexity. New approaches are needed for how data is collected and filtered, processed, moved, stored and analysed if these challenges are to be met with a realistic budget. To develop innovative techniques we are fostering relationships with industry leaders. CERN openlab is a unique resource for public-private partnership between CERN and leading Information Communication and Technology (ICT) companies. Its mission is to accelerate the development of cutting-edge solutions to be used by the worldwide HEP community. In 2018, CERN openlab started its phase VI with a strong focus on tackling the upcoming LHC challenges. Several R&D programs are ongoing in the R&D areas of data centre technologies and infrastructures. computing performance and software, machine learning and data analytics. This talk gives an overview of the various innovative technologies that are currently being explored by CERN openlab VI and discusses the long-term strategies that are pursued by the LHC communities with the help of industry in closing the technological gap in processing and storage needs expected in Run3 and Run4.
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Instrumentation Division Seminar
"The ATLAS ITK Strip Detector for High-Luminosity LHC"
Presented by Stefania Stucci, CERN, Italy
Tuesday, May 22, 2018, 2:30 pm
Large Conference Room, Bldg. 535The High-Luminosity LHC operations are scheduled to start in 2026. The ATLAS experiment is currently preparing for an upgrade of the inner tracking detector. The radiation damage at the maximum integrated luminosity of 4000/fb implies integrated hadron fluencies over 2x10^16 neq/cm2 requiring replacement of the existing Inner Detector. An all-silicon Inner Tracker (ITk) is proposed with a pixel detector surrounded by a strip detector. The current prototyping phase, targeting an ITk Strip Detector consisting of a four-layer central barrel and forward regions composed of six disks at each end, will be described. In this contribution I will present the design of the ITk Strip Detector and the preparations for production.
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Nuclear Physics Seminar
"TMD evolution as a double-scale evolution"
Presented by Alexey Vladimirov, Universitat Regensburg
Tuesday, May 15, 2018, 11 am
Small Seminar Room, Bldg. 510Hosted by: Oleg Eyser
Transverse momentum dependent (TMD) distributions depend on the pair of scaling parameters and their evolution is given by a pair of coupled equations. I present the analysis of the TMD evolution equations and their solution with the emphasis on their two-dimensional structure. It results in a new viewpoint on TMD evolution, both from the technical and interpretation sides. I formulate the non-perturbative definition of zeta-prescription and introduce the notion of optimal TMD distribution. I demonstrate that the updated form of TMD evolution produces lesser theoretical uncertainty and improves agreement with the data.
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HET/RIKEN Lunch Seminar
"Quantum Simulation from Quantum Chemistry to Quantum Chromodynamics"
Presented by Peter Love, Tufts
Thursday, May 10, 2018, 12:30 pm
Building 510, Room 2-160Hosted by: Mattia Bruno and Enrico Rinaldi
Quantum simulation proposes to use future quantum computers to calculate properties of quantum systems. In the context of chemistry, the target is the electronic structure problem: determination of the electronic energy given the nuclear coordinates of a molecule. Since 2006 we have been studying quantum approaches to quantum chemical problems, and such approaches must face the challenges of high, but fixed, precision requirements, and fermion antisymmetry. I will describe several algorithmic developments in this area including improvements upon the Jordan Wigner transformation, alternatives to phase estimation, adiabatic quantum computing approaches to the electronic structure problem, methods based on sparse Hamiltonian simulation techniques and the potential for experiments realizing these algorithms in the near future. I will also briefly review work by others on the analog and digital simulation of lattice gauge theories using quantum simulators.
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Physics Colloquium
"The Cosmic Microwave Background and How It Keeps on Revealing More about the Universe"
Presented by Suzanne Staggs, Princeton
Tuesday, May 8, 2018, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Andrei Nomerotski
In the 50+ years since its discovery, the cosmic microwave background (CMB) has yielded surprisingly detailed and precise information about the form, content and dynamics of the early universe. High angular resolution maps, and polarization data at all angular scales, are the focus of current and next-generation instruments. I will describe what we already know about the universe from the CMB, and lay the ground for future revelations from the CMB, with special emphasis on the Atacama Cosmology Telescope (ACT). ACT is a special-purpose 6m telescope situated at 17,000 ft in the dry Atacama Desert of northern Chile, at a latitude of 23 degrees South. ACT's millimeter-wave detectors measure both polarization and intensity at very fine angular scales (arcminutes). I will describe the ACT instrument and its data in the context of other ongoing and proposed CMB projects, their scientific impact, and the potential discovery space. I will include a brief description of the upcoming Simons Observatory.
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Condensed-Matter Physics & Materials Science Seminar
"Picoastronomy: an electron microscopist's view of the history of the Solar System"
Presented by Rhonda Stroud, US Naval Research Laboratory
Friday, May 4, 2018, 2 pm
Bldg. 480, Conference RoomHosted by: Yimei Zhu
A wide range of astrophysical processes, from condensation of dust particles in circumstellar envelopes to space weathering on airless bodies, are inherently pico-to-nanoscale phenomena. Thus an electron microscope, used for direct observation of planetary materials in the laboratory, can be as much of an astronomical tool as a telescope pointed at the sky. The energy resolution of state-of-the-art monochromated scanning transmission electron microscopes (STEMs), as low as 10 meV, makes it possible to directly observe the infra-red optical properties of individual cosmic dust grains in the 5 to 25 um range. Thus, distinguishing the 10-um and 18-um features of individual bonafide astrosilicates is now possible. The identity of volatiles, trapped in individual nanoscale vesicles, can be determined with STEM-EELS to better constrain space weathering processes in lunar soils. Finally, STEM-EDS offers to possibility of constraining noble gas contents of primitive carbonaceous materials, including nanodiamond, and "phase Q", thus thus constrain their formation histories.
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Particle Physics Seminar
"Beam Dynamics Measurements for the Muon g-2 Experiment at Fermilab"
Presented by Dr. Tammy Walton, Fermilab
Thursday, May 3, 2018, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Chao Zhang
There exists a > 3 sigma discrepancy between the experimental measurement and Standard Model prediction of the anomalous magnetic moment for the muon. The Muon g-2 experiment at Fermilab will reduce the experimental uncertainty of 540 ppb to 140 ppb, which includes improving the systematic uncertainty by a factor of 3. A significant reduction in the systematic uncertainty for sources associated with the dynamics of the muon beam are needed in order to achieve the expected goal. The experiment is operational and accumulating physics data. The presentation focus on measuring the spatial distribution and dynamics of the muon beam using high advanced tracking detectors. In addition, beam dynamics measurements using other detector systems are presented. By taking advantage of the different detector systems, the Fermilab's experiment is highly equipped to control the various sources contributing to the muon beam-related uncertainties.
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Physics Colloquium
"The Muon g-2 Experiment at Fermilab"
Presented by Tammy Walton, FNAL- Leona Woods Lectureship award winner's colloquium
Tuesday, May 1, 2018, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Andrei Nomerotski
The Muon g-2 experiment at Fermilab is measuring the anomalous magnetic dipole moment of the muon with an improved factor of four accuracy (140 ppb). The new measurement is inspired by the > 3s discrepancy between the Brookhaven experimental measurement and Standard Model prediction, where the discrepancy gives hints of new physics beyond the Standard Model. The Fermilab's Muon g – 2 experiment is taking physics data and is projected to accumulate 1 x BNL statistics by the end of the spring 2018 Fermilab's accelerator shutdown. In this presentation, I will discuss the scientific motivation and physics of muon g – 2 experiments and conclude with a snapshot of data results from the beginning of the physics run.
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Condensed-Matter Physics & Materials Science Seminar
"Chemistry beyond the crystal- advanced Fourier techniques"
Presented by Simon Kimber, Oak Ridge National Laboratory
Monday, April 30, 2018, 1:30 pm
ISB Bldg. 734 Conf. Rm. 201 (upstairs)Hosted by: Ian Robinson
Chemical crystallography nowadays makes structure determination and refinement trivial. However, advances in x-ray and neutron sources mean that we should revisit some of the basic assumptions that shape our experiments. For example, most chemical reactivity in e.g. catalysis, self-assembly etc, occurs in the solution phase. Why are we as crystallographers then wedded to the solid state? In this presentation, I will show how total scattering can be used to determine changes in cluster structure during photochemical reactions and to probe the role of the solvent in 'magic size' cluster formation. I will then describe how neutron scattering techniques can be used to challenge another basic assumption- the static approximation in total scattering. We have successfully applied so-called 'dynamic-PDF' techniques to simple chalcogenide materials. This allows to determine the time scale on which local distortions appear, providing insight into the role of highly anharmonic phonons in e.g. phase change and thermoelectric materials. Time allowing, I will also provide a short update on progress at ORNL, including the upcoming restart of the SNS, and new instrumentation for diffraction, total and diffuse scattering.
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Nuclear Theory/RIKEN Seminar
"Exploring the QCD phase structure with functional methods"
Presented by Bernd-Jochen Schaefer, University of Giessen
Friday, April 27, 2018, 2 pm
Building 510, CFNS Seminar Room 2-38Hosted by: Chun Shen
QCD at finite temperature and moderate densities predicts a phase transition from a chiral symmetry broken hadronic phase to a chirally restored deconfined quark-gluon plasma phase. In this talk I report on recent progress achieved basically with functional renormalization group (FRG) methods to reveal the QCD phase structure. Two and three quark flavor FRG investigations are confronted to results obtained with effective chiral low-energy models. The importance of quantum and thermal fluctuations is demonstrated and their consequences for the experimental signatures to detect possible critical endpoints in the phase diagram are discussed.
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CFNS Seminar
"Polarized light ion physics with spectator tagging at EIC"
Presented by Christian Weiss, Jefferson Lab
Thursday, April 26, 2018, 4 pm
CFNS Seminar Room, Bldg. 510, Room 2-38Hosted by: Andrey Tarasov
Measurements of deep-inelastic scattering (DIS) on polarized light ions (deuteron, 3He, ...) address important physics topics such as the spin structure of the neutron, nuclear modifications of parton densities, and coherent effects at small x. Detection of the nuclear breakup state ("spectator tagging") reveals the nuclear configurations present during the high-energy process and permits a controled theoretical treatment of nuclear effects. We report about an on-going effort to develop the theoretical and experimental methods for spectator tagging with the deuteron at EIC. This includes (a) the description of nuclear structure and breakup in DIS using methods of light-front quantization; (b) extraction of free neutron spin structure from tagged DIS using on-shell extrapolation; (c) novel studies of nuclear shadowing in diffractive tagged DIS at small x; (d) the forward detector and ion beam requirements for spectator tagging at EIC. We present suggestions for future physics studies and detailed process simulations.
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Condensed-Matter Physics & Materials Science Seminar
"Topological properties of Weyl semimetals in the presence of randomness"
Presented by Jedediah Pixley, Rutgers
Wednesday, April 25, 2018, 1:30 pm
ISB Bldg. 734 Conf. Rm. 201 (upstairs)Hosted by: Laura Classen
We will discuss the effects of short-range disorder on three-dimensional Weyl semimetals with a focus on the topological Fermi arc surface states and the existence of the axial anomaly in the presence of parallel electric and magnetic fields. We will briefly review the bulk properties of disordered Weyl semimetals concentrating on the proposed quantum critical point separating a semimetal and diffusive metal phase driven by disorder. We show that quasi-localized, rare eigenstates contribute an exponentially small but non-zero density of states at the Weyl node energy. This destabilizes the semimetal phase and converts the semimetal-to-diffusive metal transition into a cross over (dubbed an avoided quantum critical point). In turn, it is no longer obvious how robust the topological properties are in these materials. We will therefore discuss the effects disorder has on the robustness of Weyl Fermi arc surface states and the axial anomaly. We find that the Fermi arcs, in addition to having a finite lifetime from disorder broadening, hybridize with the non-perturbative bulk rare states, which unbinds them from the surface (i.e. they lose their purely surface spectral character). Nonetheless, the surface chiral velocity is robust and survives in the presence of strong disorder. Lastly, we will discuss the robustness of the axial anomaly for a single Weyl cone in the presence of disorder. We will show that deep in the diffusive limit, when a band structure picture of dispersing (chiral) Landau levels no longer applies, the axial anomaly survives.
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Physics Colloquium
"Nature vs. Nurture in Complex (and Not-So-Complex) Systems"
Presented by Daniel Stein, NYU
Tuesday, April 24, 2018, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Rob Pisarski
Understanding the dynamical behavior of many-particle systems following a deep quench is a central issue in both statistical mechanics and complex systems theory. One of the basic questions centers on the issue of predictability: given a system with a random initial state evolving through a well-defined stochastic dynamics, how much of the information contained in the state at future times depends on the initial condition (``nature'') and how much on the dynamical realization (``nurture'')? We discuss this question and present both old and new results for both homogeneous and random systems in low and high dimension.
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Condensed-Matter Physics & Materials Science Seminar
"Building and understanding magnetic nano-structures, one atom at a time"
Presented by Adrian Feiguin, Northeastern University
Tuesday, April 24, 2018, 1:30 pm
ISB Bldg. 734 Conf. Rm. 201 (upstairs)Hosted by: Alexei Tsvelik
In the past decade we have witnessed enormous progress in experiments that consist of placing magnetic atoms at predetermined positions on substrates and building magnetic nanostructures one atom at a time. The effective interaction between spins is mediated by the conduction electrons in the substrate. In order to understand these interactions, we rely on a theory developed decades ago by Ruderman, Kittel, Kasuya, and Yosida, dubbed "RKKY theory", which applies when the spins are classical. The quantum nature of the electronic spin introduces another degree of complexity and competition with another quantum phenomenon: the Kondo effect. This competition is quite subtle and non-trivial, and can only be studied by numerical means. We investigate this mechanism on different lattice geometries in 2 and 3 dimensions by introducing an exact mapping onto an effective one-dimensional problem that we can solve with the density matrix renormalization group method (DMRG). We show a clear and departure from the conventional RKKY theory, and important differences that can be attributed to the dimensionality and geometry. We have found that there is a critical distance at which the Kondo effect dominates, translating into a finite range for the RKKY interaction. In particular, for dimension d>1, Kondo physics dominates even at short distances, while the ferromagnetic RKKY state is energetically unfavorable. Remarkably, in the case of impurities with higher spin S=1, both effects can co-exist: while the impurities are partially screened by the conduction electrons, an effective dangling spin S=1/2 is responsible for the entanglement between impurities.
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Nuclear Physics Seminar
"Fictions, fluctuations and mean fields"
Presented by Pasi Huovinen, Uniwersytet Wroclawski
Tuesday, April 24, 2018, 11 am
Small Seminar Room, Bldg. 510Hosted by: Oleg Eyser
The difference between fluctuations and correlations as calculated using lattice QCD from the values evaluated using hadron resonance gas model, has been taken as an indication that there must be more resonance states then observed so far. In this talk I explore how the fluctuations and correlations change if I include the unobserved states (fictions) predicted by a quark model to the hadron resonance gas, and, on the other hand, how the fluctuations and correlations change if we include the repulsive interactions between baryons and antibaryons in the hadron resonance gas model using repulsive mean field.
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Particle Physics Seminar
"Signal Processing in Single-Phase LArTPCs - Application at MicroBooNE"
Presented by Brooke Russell, Yale University, Wright Laboratory
Thursday, April 19, 2018, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Chao Zhang
The single-phase liquid argon time projection chamber (LArTPC) is a burgeoning detector technology with extensive use in existing and planned accelerator neutrino experiments. While engineering challenges in developing this technology have largely been overcome, high-quality reconstruction of the detailed topological and calorimetric information provided by the fine-grained drifted ionization charge signal is still in active development. In this talk, I describe a robust ionization charge extraction method developed at MicroBooNE and generically applicable to all single-phase LArTPC experiments. This technique accurately converts the raw digitized TPC waveforms into the number of ionization electrons from both induction and collection wire planes. The performance of cold electronics is critical to the success of signal extraction methods. I motivate how characterization and suppression of detector noise translates to signal processing proficiency. Finally, I relate the performance of signal processing to the context of MicroBooNE's physics goals and prospects to realize the promised capability of LArTPC detector technology.
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Physics Colloquium
"Plasma science - From laboratory-fusion to astrophysical plasmas"
Presented by Fatima Ebrahimi, Princeton Plasma Physics Laboratory and Princeton University
Tuesday, April 17, 2018, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Rob Pisarski
Our universe is immersed in magnetized plasma, electrically conducting ionized gas. Some of the most fundamental and long-standing astrophysical problems, such as the magnetization of the universe, collimation of astrophysical jets, the accretion process and transport in astrophysical disks (surrounding e.g. black holes) and their coronas can only be explored through plasma physics. Our sun as a natural laboratory for plasma physics provides inspiring as well as challenging problems, including its dynamo cycles, heating, and the replication of its core reaction, fusion energy, on earth in a lab. There is an abundance of observational/experimental data emerging from natural phenomena of space and astrophysical plasmas, as well as laboratory plasma experiments, for plasma physicists to explore. I will review some of these topics, in particular magnetic reconnection, the rearrangement of the magnetic ?field topology of plasmas, which energizes many processes in nature and has been shown to also be critical in the nonlinear dynamics of many processes in toroidal fusion plasmas. Using global simulations, I will demonstrate the instrumental role of magnetic reconnection, which enables an innovative technique for producing current in fusion plasmas.
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Particle Physics Seminar
"First Results from CUORE - Search for Neutrinoless Double Beta Decay in 130Te"
Presented by Karsten Heeger, Yale University, Wright Laboratory
Thursday, April 12, 2018, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Chao Zhang
The Cryogenic Underground Observatory for Rare Events (CUORE) is a ton-scale cryogenic experiment at Gran Sasso National Laboratory designed to search for neutrinoless double-beta decay (0νββ) in tellurium-130. The experiment consists of 988 ultracold tellurium dioxide bolometric crystals, which act as both the double-beta decay sources and detectors. An observation of neutrinoless double-beta decay would be direct evidence of lepton number violation and unambiguously prove that neutrinos are Majorana particles. This talk presents the first results from CUORE based on an exposure of 83.6 kg yr of tellurium dioxide. With this data we find no evidence for neutrinoless double-beta decay and set the world-leading limit on the rate of 0νββ in 130Te
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Physics Colloquium
"Quantum Chromodynamics in the Exascale Era with the Emergence of Quantum Computing"
Presented by Martin Savage, University of Washington
Tuesday, April 10, 2018, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Peter Petreczky
A century of coherent experimental and theoretical investigations uncovered the laws of nature that underly nuclear physics ? Quantum Chromodynamics (QCD) and the electroweak interactions. While analytic techniques of quantum field theory have played a key role in understanding the dynamics of matter in high energy processes, they become inapplicable to low-energy nuclear structure and reactions, and dense systems. Expected increases in computational resources into the exascale era will enable Lattice QCD calculations to determine a range of important strong interaction processes directly from QCD. However, important finite density systems, non equilibrium systems, and inelastic processes are expected to remain a challenge for conventional computation. In this presentation, I will discuss the state-of-the-art Lattice QCD calculations, progress that is expected in the near future, and the potential of quantum computing to address Grand Challenge problems in nuclear physics.
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Nuclear Theory/RIKEN Seminar
"Dense nuclear and quark matter from holography"
Presented by Andreas Schmitt, University of Southampton
Friday, April 6, 2018, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Chun Shen
QCD at large, but not asymptotically large, baryon density presents an enormous theoretical challenge because first-principle calculations are nearly impossible. Phenomenologically, dense QCD is of great interest for the interior of neutron stars, in particular after the recent detection of gravitational waves from neutron star mergers. I will discuss a holographic approach to dense matter, making use of the Sakai-Sugimoto model, which can account for both nuclear matter and quark matter and the transition between them. In particular, nucleons are implemented as instantons in the bulk, and I will discuss certain approximations for many-nucleon matter based on the flat-space instanton solution and present the resulting phase diagrams.
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Particle Physics Seminar
"Time for High Luminosity – a new Detector for ATLAS"
Presented by Joern Lange, Institut de Fisica d'Altes Energies (IFAE) Barcelona
Thursday, April 5, 2018, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Alessandro Tricoli
To extend its physics reach, the Large Hadron Collider at CERN will be upgraded in 2024-2026 to deliver proton-proton collisions at 5-10 times higher luminosities than designed (HL-LHC). This will be a challenge for the ATLAS experiment that has to cope with higher particle densities, radiation and event pile-up of up to 200 interactions per bunch crossing. Apart from the planned exchange of the full inner tracker, a complete new detector is being proposed and developed to complement precise tracking with ultra-fast timing: the High Granularity Timing Detector (HGTD). It will exploit the fact that the primary vertices where the individual interactions take place are not only distributed in space, but also in time. Hence, measuring the time of each particle with about 30 ps precision allows to further suppress backgrounds from pile-up and restore the reconstruction performance of b-tagging, jets, isolated leptons and missing transverse energies, which is crucial for many physics analyses. The HGTD will cover a pseudo-rapidity range of 2.4 to 4.0 with a granularity of 1.3x1.3 mm2. It is only made possible by the rapid advance of a new silicon detector technology, namely Low Gain Avalanche Detectors (LGAD), which have been developed by CNM Barcelona and the CERN RD50 Collaboration and are now also produced by Hamamatsu, FBK, BNL and Micron. It has been shown that LGADs can fulfill the challenging HGTD requirements, especially also after the high radiation fluence levels expected at the end of life time of up to 5e15 neq/cm2. This presentation will motivate and introduce the HGTD and present the new LGAD sensor technology including performance measurements before and after irradiation. New developments such as 4D-tracking and possible other applications inside and outside High Energy Physics (forward detectors like AFP, low-energy X-rays, radio-therapy) will be discussed as well.
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Condensed-Matter Physics & Materials Science Seminar
"Plastic Deformation at the Nanoscale and Superconductivity Enhancement in Decompression"
Presented by Bin Chen, Shanghai Laboratory of Center for High Pressure Science & Technology Advanced Research (HPSTAR), China
Thursday, April 5, 2018, 1:30 pm
ISB Bldg. 734 Seminar Room 201 (upstairs)Hosted by: Cedomir Petrovic
Plastic Deformation at the Nanoscale: Understanding the plastic deformation of nanocrystalline materials is a longstanding challenge [1,2]. Various controversial observations, mainly on the existence of dislocations and the mechanisms for a reversed Hall–Petch effect, have been reported. However, in situ observation of plastic deformation in ultrafine (sub-10 nm) nanocrystals has long been difficult, precluding the direct exploration of mechanics at the nanometer scale. By using a radial diamond-anvil cell (rDAC) x-ray diffraction technique we plastically deformed nickel to pressures above 35 GPa and observed that 1) dislocation-mediated deformation was still operative in as small as 3 nm nickel particles [3]; 2) 70 nm nickel particles were found to rotate more than any other grain size, signaling the reversal in the size dependence of grain rotation [4,5]; 3). Hall-Petch effect in nickel can be extended to 3 nm [6]. These observations demand considering the role of defects in the physical behaviors of nanomaterials. Superconductivity Enhancement in Decompression: An unexpected superconductivity enhancement was recently observed in decompressed In2Se3 [7]. The onset of superconductivity in In2Se3 occurred at 41.3 GPa with a critical temperature (Tc) of 3.7 K, peaking at 47.1 GPa. The striking observation shows that this layered chalcogenide remains superconducting during decompression down to 10.7 GPa. More surprisingly, the highest Tc in decompression was 8.2 K, a twofold increase in the same crystal structure as in compression. The novel decompression-induced superconductivity enhancement implies that it is possible to maintain pressure-induced superconductivity at lower or even ambient pressures with better superconducting performance. References: [1] B. Chen, et al., MRS Bulletin 41, 473 (2016). [2] H. K. Mao, et al., Matter and Radiation at Extremes, 1, 59 (2016). [3] B. Chen, et al., Science 338, 1448 (2012). [4] B. Chen, et al., Proc. Natl. Ac
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Physics Colloquium
"Eigenstate thermalization and its implications to statistical mechanics"
Presented by Anatoli Polkovnikov, Boston University
Tuesday, April 3, 2018, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Rob Pisarski
In this talk I will overview recent developments in understanding quantum chaos through random matrix theory. I will discuss various conjectures on the nature of quantum stationary states in chaotic systems and show numerical evidence supporting them. It is the random nature of eigenstates, which ultimately leads to loss of information about initial conditions and leads to emergence of statistical mechanics in isolated systems. I will then introduce the so-called Eigenstate Thermalization Hypothesis (ETH) ansatz first proposed by J. Deutsch and M. Srednicki in 90th, which gives a unified framework for the structure of physical observable in quantum chaotic systems. I will demonstrate how the ETH ansatz naturally leads to emergence of various thermodynamic relations. At the end of the talk I will mention some open problems.
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Condensed-Matter Physics & Materials Science Seminar
"Non-abelian symmetries and applications in tensor networks"
Presented by Andreas Weichselbaum, Brookhaven National Lab
Thursday, March 29, 2018, 1:30 pm
ISB Bldg. 734 Conf. Rm. 201 (upstairs)Hosted by: Igor Zaliznyak
I will give a brief introduction to tensor network states with focus on exploiting all symmetries, abelian and non-abelian alike. I will briefly motivate a generic framework for finite-dimensional Lie algebras, which has been fully implemented in the tensor library QSpace [1]. The latter was already put under extensive scrutiny over the past couple of years. Along it already also gave rise to a range of excellent applications. Here, in particular, I will briefly highlight 1D density matrix renormalization group (DMRG) calculations on SU(N) Heisenberg ladders, 2D projected entangled pair state (PEPS) simulations on Spin-1 Kagome [2], and infinite-dimensional dynamical mean-field theory (DMFT) simulations on Hund's metals [3]. [1] A. Weichselbaum, Annals of Physics 327, 2972 (2012) [2] Liu et al., PRB 91 (R), 060403(R) (2015) [3] Stadler et al. PRL 115, 136401 (2015)
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Condensed-Matter Physics & Materials Science Seminar
"Accurate spectral calculations for testing electronic structures, low energy excitations, and vibronic interactions"
Presented by Keith Gilmore, The European Synchrotron Radiation Facility, France
Thursday, March 29, 2018, 11 am
ISB Bldg. 734 Conf. Rm. 201 (upstairs)Hosted by: Robert Konik
Resonant inelastic x-ray scattering (RIXS) is a relatively new technique for probing low energy excitations in materials. In addition to traditional techniques, such as angle resolved photoemission, it has become an important, high precision characterization tool of strongly correlated electron materials. To calculate RIXS, and related core and valence level spectra, we solve the Bethe-Salpeter equation (BSE) based on a self-energy corrected density functional theory electronic structure. I outline our implementation of the BSE and use SrVO3 for demonstration. The sensitivity of spectral features to the self-energy approximation – whether G0W0, qpscGW, or DMFT – is highlighted. To include interactions beyond the usual BSE I introduce the cumulant expansion. Spectral functions derived from a GW self-energy are typically inadequate when the dressed Green's function is built via the Dyson equation. With the same GW self-energy, a superior Green's function and spectral function, implicitly including vertex corrections, is obtained through the cumulant expansion. I consider application of the GW-cumulant expansion to photoemission, photoabsorption, and X-ray scattering. Lastly, vibronic coupling has important impacts on these spectra. I show how to calculation the phonon contribution to photoemission, absorption and scattering with a vibronic cumulant.
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Physics Colloquium
"Particles Colliders: Past, Present and Future"
Presented by Dmitri Denisov, Fermilab
Tuesday, March 27, 2018, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Andrei Nomerotski
Developments of the particle colliders over last 50 years have seen tremendous progress in both the energy of the collisions and the intensity of the colliding beams. In order to reach even higher collision energy many fundamental inventions in the colliders design have been achieved. Progress to even higher energies was strongly stimulated by physics interests in studying smaller and smaller distances and in creation of heavier and heavier elementary particles. Experiments at colliders required major breakthroughs in the particle detection methods in order to discover new particles such as c and t quarks, gluons, tau lepton, W, Z and Higgs bosons which completed currently expected set of elementary particles. Options for even higher energy colliders will be discussed, including their design parameters, acceleration principles as well as construction challenges. Such colliders is the only way to understand the Nature at even smaller distances and create particles with higher masses than we can reach today.
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Physics Colloquium
"Nuclear lattice simulations"
Presented by Dean Lee, Michigan State University
Tuesday, March 20, 2018, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Peter Petreczky
This is an introduction to how atomic nuclei and other quantum few- and many-body systems can be studied using lattice simulations. The first part of the talk explains the basic formalism called lattice effective field theory. The rest of the talk is a discussion of novel methods and the new physics insights one gains with each. The methods discussed are the adiabatic projection method for scattering and reaction calculations, pinhole algorithm for probing structure and thermodynamic properties, and eigenvector continuation for extending calculations to regions of parameter space where things otherwise break down.
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Condensed-Matter Physics & Materials Science Seminar
"Spatial Resolution of Low-Loss EELS"
Presented by R.F. Egerton, University of Alberta, Canada
Tuesday, March 20, 2018, 2 pm
Building 480 Conference RoomHosted by: Yimei Zhu
Recent-generation TEM/STEM instruments fitted with an electron monochromator provide an energy resolution down to 0.01 eV for electron energy-loss spectroscopy (EELS) and are themselves capable of achieving a spatial resolution approaching 0.1 nm. Besides offering the possibility of vibrational-mode EELS for examining chemical bonds, these instruments could be useful for mapping the electronic properties (e.g. band gap) of insulators and semiconductors. However, basic physics imposes a spatial resolution of few nm (or tens of nm) for energy loss below 10 eV, due to delocalization of the inelastic scattering. We will discuss what might be done to improve the spatial resolution, to make low-loss EELS competitive with other techniques.
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Nuclear Physics Seminar
"Probing the collectivity of heavy quarks in pPb collisions with prompt D0 elliptic flow using CMS detector"
Presented by Zhenyu Chen, Rice University
Tuesday, March 20, 2018, 11 am
Small Seminar Room, Bldg. 510Hosted by: Lijuan Ruan
Recent years, evidence for collective effects has been revealed in pp and pPb collisions when looking at events releasing large number of particles. The experimental observations lead to a debate of the formation of strongly coupled Quark-Gluon Plasma in those small collision systems. Azimuthal anisotropy coefficient (vn) of heavy-flavor particles, and especially the comparison to light flavor particles vn, can shed light on the strength of the coupling between heavy flavor quarks and the hypothesized hydrodynamic medium at a significantly reduces size, and impose further constrains on different interpretations related to the origin of the observed collectivity. In this talk, the most recent results of prompt D0 meson elliptic flow (v2) in high-multiplicity pPb collisions are presented over a wide transverse momentum range. The results are compared to those of strange hadrons, including Kshort, Lambda, Cascade and Omega particles.
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Nuclear Theory/RIKEN Seminar
"Correlators of twist-2 light-ray operators in the BFKL approximation"
Presented by Ian Balitsky
Friday, March 16, 2018, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Andrey Tarasov
It is well known that BFKL gives anomalous dimensions of twist-2 operators of spin j in the "BFKL limit'' $g^2\righarrow 0,\omega\equiv j-1\righarrow 0,{g^2\over\omega}$ fixed. I demonstrate that such limit describes the non-local light-ray operators and present the results of calculation of two- and three-point correlation functions of these operators in this limit. The calculation is performed in ${\cal N}$=4 SYM but the result is valid in other gauge theories such as QCD.
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Condensed-Matter Physics & Materials Science Seminar
"Quantum dimer models for high temperature superconductors"
Presented by Garry Goldstein, Cambridge University, United Kingdom
Friday, March 16, 2018, 1:30 pm
ISB Bldg. 734 Conf. Rm. 201 (upstairs)Hosted by: Robert Konik
In this talk we review the slave boson meanfield formulation of the fermion+boson quantum dimer model for the pseudogap phase of the high temperature superconductors. We show that in the presence of weak slowly varying external magnetic and electric fields the fermionic dimers undergo semiclassical motion in the external field. As a result in the presence of magnetic fields strong enough to destroy superconductivity the dimers undergo quantum oscillations. Indeed they satisfy Onsager quantization for their orbits and Lifshtiz-Kosevich formula for the amplitude of oscillations. We also compute the effective charges of the dimers in the presence of external magnetic fields as a function of temperature. We show that the effective magnetic charge changes sign from negative −e at low temperature to positive +e at high temperature. This leads to a change of the sign of the Hall coeÿcient as a function of temperature. We also compute the magnetoresistance as a function of the external field and temperature within a linearized Boltzmann equation approximation for the fermionic dimers. Furthermore we further show that the dimers undergo a Lifshitz transition as a function of doping with a van Hove singularity appearing at the Fermi surface near optimal doping ∼ 20%. Indeed the van Hove singularity leads to a divergence of the density of states and as such an optimum Tc. We study the interplay of nematic fluctuations and the van Hove singularity both of which occur near optimal doping. We show that the van Hove singularity modifies the critical properties of the QCP (quantum critical point) for nematic fluctuations and that the QCP may be described by Hertz Millis like theory with z = 4. This allows us to calculate the critical exponents of the nematic fluctuations and to show that the fermionic dimers have non-Fermi liquid behavior near the QCP with the self energy diverging ∼ |ω3/4| near the QCP.
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Particle Physics Seminar
"Precision Measurements of Asymmetries and Spectra in Neutron Decay"
Presented by Brad Plaster, University of Kentucky
Thursday, March 15, 2018, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Chao Zhang
Precision measurements of various asymmetries in neutron decay permit an extraction of the weak axial-vector coupling constant, gA, a fundamental quantity important for weak-interaction physics and as a benchmark for lattice QCD calculations. I will discuss a recent new result from the UCNA Experiment at Los Alamos National Laboratory for a 0.16% precision result on gA from a measurement of the 'A' asymmetry, which represents the parity-violating angular correlation between the neutron's spin and the decay electron's momentum. This long-standing effort was carried out with a superconducting solenoidal electron spectrometer at the LANL Ultracold Neutron (UCN) facility. This new result will be placed in the context of historical results for gA and recent discrepant values for the neutron lifetime obtained via different experimental techniques. I will also discuss the first-ever extraction of the Fierz interference term 'b' in free neutron decay from an analysis of the electron's spectral shape as measured in the UCNA Experiment. A non-zero 'b' term would result from beyond-Standard Model interactions, such as Scalar or Tensor physics. Although the result for 'b' from the UCNA Experiment was systematics limited, it points to the requisite significant improvements in the characterization of the detector energy response that future experiments aimed at a measurement of 'b' will need to achieve in order to probe beyond Standard Model physics at a competitive precision.
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Condensed-Matter Physics & Materials Science Seminar
"Splitting of electrons and violation of the Luttinger sum rule"
Presented by Eoin Quinn, University of Amsterdam, Netherlands
Thursday, March 15, 2018, 1:30 pm
ISB Bldg. 734 Conf. Rm. 201 (upstairs)Hosted by: Robert Konik
We obtain a controlled description of a strongly correlated regime of electronic behaviour. We argue that there are two ways to characterise the electronic degree of freedom, either by the canonical fermion algebra or by the graded Lie algebra su(2|2). The first underlies the Fermi liquid description of correlated matter, and we identify a novel regime governed by the latter. We obtain the electronic spectral function within a controlled approximation, and find a splitting in two of the electronic band. The Luttinger sum rule is violated and a Mott metal-insulator transition is exhibited.
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Condensed-Matter Physics & Materials Science Seminar
"Enabling emergent spin-orbit magnetism in iridate-based heterostructures"
Presented by Jian Liu, The University of Tennessee, Knoxville
Thursday, March 15, 2018, 11 am
ISB Bldg. 734 Seminar Room 201 (upstairs)Hosted by: Mark Dean
5d transition metal oxides have emerged as a novel playground for some of the most outstanding and challenging problems in condensed matter physics, such as metal-insulator transition and quantum magnetism. In particular, layered iridates hosting square lattices of IrO6 octahedra have drawn significant interests due to the electronic and magnetic analogy with high-Tc cuprates. However, materials of this kind are limited to a few Ruddlesden-Popper (RP) compounds. In this talk, I will discuss our recent work on overcoming this bottleneck by constructing such two-dimensional (2D) structures confined in superlattices grown by heteroepitaxy. By leveraging the layering control of epitaxial growth, we are not only able to develop new structural variants of layered iridates, but also unravel and exploit the intriguing spin-orbit-driven 2D magnetism beyond the cuprate physics yet invisible in the RP iridates. The results demonstrate the power of this approach in tailing the exchange interactions, enabling new magnetic controls, and providing unique insights into the emergent phenomena of 5d electrons.
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Particle Physics Seminar
"From first beam to particle physics discoveries with petabytes of data"
Presented by Paul Laycock, CERN
Monday, March 12, 2018, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Alessandro Tricoli
The LHC experiments require huge, ever-increasing volumes of data to explore the frontiers of particle physics, and the grid provides the infrastructure to meet this challenge. Today, even medium sized experiments produce petabytes of data that need to be analysed by international collaborations and the relationship between particle physicists and their data has had to evolve to keep pace. Calibrating and systematically understanding detectors requires detailed information, deep learning algorithms promise to allow us to fully exploit our experiments, and on the other hand we want to analyse our data quickly and be the first to publish. This talk will first describe how, shortly after the Higgs discovery, ATLAS realised that the way that analysis was done had to change, and will briefly illustrate what those changes entailed. Next, the NA62 experiment will be described. Recording a billion events per day, NA62 aims to measure the very rare decay of a charged kaon to a charged pion and two neutrinos. The collaboration had to quickly implement petabyte scale data processing infrastructure to perform the sub-nanosecond calibrations needed to challenge the 10% precision of the theory prediction.
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Nuclear Theory/RIKEN Seminar
"Yang-Mills action on the light front: MHV amplitudes and Wilson lines"
Presented by Anna Stasto, Penn State
Friday, March 9, 2018, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Chun Shen
The MHV action is the Yang-Mills action quantized on the light-front, where the two explicit physical gluonic degrees of freedom have been canonically transformed to a new set of fields. This transformation leads to the action with vertices being off-shell continuations of the MHV amplitudes. We show that the solution to the field transformation expressing one of the new fields in terms of the Yang-Mills field is a certain type of the Wilson line. More precisely, it is a straight infinite gauge link with a slope extending to the light-cone minus and the transverse direction. One of the consequences of that fact is that certain MHV vertices reduced partially on-shell are gauge invariant — a fact discovered before using conventional light-front perturbation theory. We also analyze the diagrammatic content of the field transformations leading to the MHV action. We found that the diagrams for the solution to the transformation (given by the Wilson line) and its inverse differ only by light-front energy denominators.
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Particle Physics Seminar
"New neutrino oscillation results from NOvA"
Presented by Jeremy Wolcott, Tufts University
Thursday, March 8, 2018, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Chao Zhang
The NOvA experiment is an off-axis long-baseline neutrino oscillation experiment using the NuMI $\nu_{\mu}$ beam originating at Fermilab. By examining the disappearance of muon neutrinos and the appearance of electron neutrinos between the near detector at Fermilab and the far detector in Ash River, MN, NOvA has the potential to help answer a number of fundamental questions: Are the neutrinos' masses ordered the same way as those of the charged leptons? Do leptons experience charge-parity violation? Are there underlying symmetries in the way the neutrino states mix with one another? In this talk I will present NOvA's most recent constraints on the answers to those questions utilizing muon neutrino disappearance and electron neutrino appearance. These updated results are based on a 50% increase in exposure relative to previous results as well as numerous simulation and analysis improvements.
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Physics Colloquium
"Quantum simulation of gauge theories in optical lattices"
Presented by Alexei Bazavov, Michigan State University
Tuesday, March 6, 2018, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Andrei Nomerotski
hile non-perturbative approaches such as lattice gauge theory led to significant advances in understanding the physics of strong interactions, many problems remain out of reach for classical computation, in particular, real-time dynamics or properties of QCD at finite baryon density that are being explored in heavy-ion collision experiments. Recent advances in the technology of engineering custom interactions for ultra-cold atomic gases in optical lattices opened a possibility for quantum simulations as was envisioned by R. Feynman in the 1980s. The main idea is that the degrees of freedom of the original system are mapped onto a quantum Hamiltonian whose dynamics can be realized in a laboratory. Many condensed matter Hamiltonians, such as Bose-Hubbard model, have been recently studied in this way. Quantum simulation of gauge theories is however challenging since the gauge symmetry is not naturally present in the ultra-cold atomic systems. I will review the current status of theoretical proposals for quantum simulation of field theories and then focus on our recent work on an explicitly gauge-invariant formulation of the Abelian-Higgs model for simulation on optical lattices.
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Instrumentation Division Seminar
"Table-top MeV laser particle accelerator @ kHz repetition rate"
Presented by Enam Chowdhury, Department of Physics, Ohio State University
Tuesday, March 6, 2018, 2:30 pm
Large Conference Room, Bldg. 535At the Extreme Light Lab at the Air Force Research Laboratory, Dayton, we explore light matter interaction at relativistic fields with liquid targets. Although demonstrations of up to 4 GeV1 electrons and ~100 MeV protons2 have been achieved in the past, all of these are not feasible as future accelerators, due to their slow duty cycle (usually single shot, rarely 1 Hz). There are many challenges to increasing the duty cycle, where laser technology, target technology, damage to system, target alignment, high repetition rate sub-micron plasma diagnostics provides nearly insurmountable obstacles. In this program, we developed ways to accelerate MeV x-rays, electrons3 and ions4 at kHz repetition rate with a small milli-joule class laser system, by developing a combination of suitable laser system, diagnostic system, target system and experimental data collection system capable of handling the high duty cycle. We also perform femtosecond-time resolution pump-probe imaging of the interaction, and extensive large scale relativistic laser plasma interaction simulations5 that reveal the nature of the acceleration processes. Such a system opens the door to extensive future application as a source for materials processing, radiation hardness testing, medical isotope production, time resolved proton probing on relativistic interactions, and many others.
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Nuclear Physics Seminar
"Looking ahead to BESII: new observables and new theoretical frameworks"
Presented by Yin Yi, MIT
Tuesday, March 6, 2018, 11 am
Small Seminar Room, Bldg. 510Hosted by: Jia Jiangyong
Upcoming beam energy scan (BES) phase II will explore the QCD phase diagram with an unprecedented precision and would potentially discover the QCD critical point. I will discuss recent theoretical developments aim at maximizing the discovery potential of BESII from both phenomenological and formal perspectives. First, I will discuss new observables which are very sensitive to the presence of the QCD critical point and are possible due to the iTPC upgrade. In the second part, I will report recent progress on understanding and describing hydrodynamic fluctuations. Remarkably, effects of hydrodynamic fluctuations can be potentially important for precise determination of shear viscosity at top RHIC energy and would play a crucial role near the QCD critical point.
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Nuclear Theory/RIKEN Seminar
"Quark / Antiquark Correlations in Heavy-Light Ion Collisions"
Presented by Matt Sievert, LANL
Friday, March 2, 2018, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Chun Shen
It has long been known that sub-nucleonic fluctuations of the energy density in the initial stages of heavy ion collisions play an important role in generating the observed distributions of particles and their flow. These energy density fluctuations are dominated by the radiation of small-x gluons which are populated to classically large occupation numbers in the wave functions of ultra-relativistic heavy ions. While these soft gluons dominate the initial conditions for the energy density, it is quark production which determines the initial conditions of other conserved charges, like flavor and baryon number. With the recent development of state-of-the art hydrodynamics codes tailored to the Beam Energy Scan which can propagate these conserved charges into the final state, it is timely and important to calculate the initial conditions of these conserved charges from first principles in QCD. In this talk, I will present new results for the spatial correlations among quarks and antiquarks produced at mid-rapidity by pair production from small-x gluons. This single-pair production mechanism, which has been studied for some time in momentum space, is the leading contribution to these correlations in coordinate space for dilute-dense collisions. As one moves from the dilute-dense regime toward the dense-dense regime, correlations due to double pair production become more important, and these correlations persist over larger length scales than the single-pair production mechanism. Over nonperturbative length scales, only the correlations from the overlap geometry remain. I will present explicit results for quark-antiquark correlations due to single pair production, and I will outline some preliminary results for the various double-pair production mechanisms. The ultimate goal of this work will be to construct a code which can initialize these conserved charges over all length scales in heavy-ion collisions.
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Condensed-Matter Physics & Materials Science Seminar
"3D non-Fermi liquid behavior from 1D critical local moments"
Presented by Laura Classen, BNL
Thursday, March 1, 2018, 1:30 pm
ISB Bldg. 734 Conf. Rm. 201 (upstairs)Hosted by: Igor Zaliznyak
We study the temperature dependence of the electrical resistivity in a system composed of critical spin chains interacting with three dimensional conduction electrons and driven to criticality via an external magnetic field. The relevant experimental system is Yb2Pt2Pb, a metal where itinerant electrons coexist with localized moments of Yb-ions which can be described in terms of effective S = 1/2 spins with dominantly one-dimensional exchange interaction. The spin subsystem becomes critical in a relatively weak magnetic field, where it behaves like a Luttinger liquid. We theoretically examine a Kondo lattice with different effective space dimensionalities of the two interacting sub-systems. We characterize the corresponding non-Fermi liquid behavior due to the "local criticality" from the spins by calculating the electronic relaxation rate and the dc resistivity and establish its quasi linear temperature dependence.
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High-Energy Physics & RIKEN Theory Seminar
"Preparing High Energy Physics Software for the Future - the Community White Paper"
Presented by Dr. Benedikt Hegner, CERN, Switzerland
Wednesday, February 28, 2018, 12 pm
Seminar Room, Bldg. 725Hosted by: Eric Lancon
Particle physics has an ambitious and broad experimental program for the coming decades. This program requires large investments in detector hardware, either to build new facilities and experiments, or to upgrade existing ones. Similarly, it requires commensurate investment into R&D of software to acquire, manage, process, and analyses the shear amounts of data to be recorded. In planning for the High Luminosity LHC in particular, it is critical that all of the collaborating stakeholders agree on the software goals and priorities, and that their efforts complement each other. In this spirit, the High Energy Physics community has created a white paper (arXiv:1712.06982) to describe and define the R&D activities required in order to prepare for this software upgrade. This presentation describes the expected software and computing challenges, and the plans to address them that are laid out in the white paper.
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Physics Colloquium
"The Multi-Messenger Picture of a Neutron Star Merger"
Presented by Brian Metzger, Columbia University
Tuesday, February 27, 2018, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Peter Petreczky
On August 17 the LIGO/Virgo gravitational wave observatories detected the first binary neutron star merger event (GW170817), a discovery followed by the most ambitious electromagnetic (EM) follow-up campaign ever conducted. A gamma-ray burst (GRB) of short duration and very low luminosity was discovered by the Fermi and INTEGRAL satellites within 2 seconds of the merger. Within 11 hours, a bright but rapidly-fading thermal optical counterpart was discovered in the galaxy NGC 4993 at a distance of only 40 Mpc. The properties of the optical transient match remarkably well predictions for kilonova emission powered by the radioactive decay of heavy nuclei synthesized in the expanding merger ejecta by the r-process. The rapid spectral evolution of the kilonova emission to near-infrared wavelengths demonstrates that a portion of the ejecta contains heavy lanthanide nuclei. Two weeks after the merger, rising non-thermal X-ray and radio emission were detected from the position of the optical transient, consistent with delayed synchrotron afterglow radiation from an initially off-axis relativistic jet with the properties consistent with those of (on-axis) cosmological short GRB. I will describe a unified scenario for the range of EM counterparts from GW170817 and their implications for the astrophysical origin of the r-process and the properties of neutron stars. I will preview the upcoming era of multi-messenger astronomy, once Advanced LIGO/Virgo reach design sensitivity and a neutron star merger is detected every few weeks.
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Condensed-Matter Physics & Materials Science Seminar
"Topological Spin Excitations in a Highly Interconnected 3D Spin Lattice"
Presented by Yuan Li, International Center for Quantum Materials, Peking University, China
Thursday, February 22, 2018, 11 am
ISB Bldg. 734 Conf. Rm. 201 (upstairs)Hosted by: Mark Dean
The recent discovery of topological semimetals, which possess distinct electron-band crossing with non-trivial topological characteristics, has stimulated intense research interest. By extending the notion of symmetry-protected band crossing into one of the simplest magnetic groups, namely by including the symmetry of time-reversal followed by space-inversion, we predict the existence of topological magnon-band crossing in three-dimensional (3D) collinear antiferromagnets. The crossing takes on the forms of Dirac points and nodal lines, in the presence and absence, respectively, of the conservation of the total spin along the ordered moments. In a concrete example of a Heisenberg spin model for a "spin-web" compound, we theoretically demonstrate the presence of Dirac magnons over a wide parameter range using linear spin-wave approximation, and obtain the corresponding topological surface states [1]. Inelastic neutron scattering experiments have been carried out to detect the bulk magnon-band crossing in a single-crystal sample. The highly interconnected nature of the spin lattice suppresses quantum fluctuations and facilitates our experimental observation, leading to remarkably clean experimental data and very good agreement with the linear spin-wave calculations. The predicted topological band crossing is confirmed [2]. [1] K. Li et al., PRL 119, 247202 (2017). [2] W. Yao et al., arXiv:1711.00632.
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Physics Colloquium
"The Social Life of Heavy Quarks"
Presented by Marek Karliner, Tel Aviv University
Tuesday, February 13, 2018, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Peter Petreczky
I will discuss recent developments regarding new types of hadrons involving heavy quarks: hadronic molecules, doubly heavy baryons, stable tetraquarks and others. I will also explain how the discovery of the doubly heavy baryon leads to quark-level analogue of nuclear fusion, with energy release per reaction an order of magnitude greater than in ordinary fusion.
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Condensed-Matter Physics & Materials Science Seminar
"Nematic superconductivity in topological materials"
Presented by Matt Smylie, Argonne National Laboratory
Tuesday, February 13, 2018, 1:30 pm
ISB Bldg. 734 Conf. Rm. 201 (upstairs)Hosted by: Genda Gu
In a topological superconductor, a bulk superconducting gap induces a symmetry-protected gapless superconducting surface state. This surface state can host exotic Majorana zero modes, which are expected to revolutionize computation technology through energy-efficient fault-tolerant quantum computing. In this talk, we will discuss the search for bulk topological superconductors and the discovery of nematic superconductivity in MxBi2Se3 (M=Cu,Sr,Nb), where the superconducting system spontaneously breaks rotational symmetry at Tc. The nematic superconducting state and possible origins of the rotational symmetry breaking will be explored, with many conventional causes being eliminated.
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Computational Science Initiative Event
"Physics Informed Machine Learning"
Presented by Michael (Mischa) Chertkov, Los Alamos National Lab
Tuesday, February 13, 2018, 10:30 am
Seminar Room, Bldg. 725Hosted by: Frank Alexander
Machine Learning (ML) capabilities are in a phase of tremendous growth, and there is great opportunity to point these tools toward physical modeling. The challenge is to incorporate domain expertise from traditional scientific discovery into next-generation ML models. We propose to develop new Physics Informed Machine Learning (PIML) algorithms that extend cutting-edge computational and algorithmic ML tools and merge them with physical knowledge in the form of constraints, symmetries, and domain expertise regarding effective degrees of freedom. This PIML methodology is illustrated on the following four enabling examples: 1. Topology and Parameter Estimation in Power Grids [based on arXiv:1710.10727] 2. Creating Turbulent Flows with Deep Learning [based on an APS/DFD2017 abstract] 3. Learning Graphical Models [Science 2018 in print; arXiv:1612.05024] 4. Renormalization of Tensor Networks (Graphical Models) [based on arXiv:1801.01649 and ICML2018 submission]
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Nuclear Theory/RIKEN Seminar
"New nonperturbative scales and glueballs in confining gauge theories"
Presented by Mohamed Anber, Lewis & Clark College
Friday, February 2, 2018, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Chun Shen
Studying confining gauge theories on a circle can provide answers to some of the deepest questions about QCD. In this talk, I start by summarizing the main characteristics shared by the compactified theories and their four dimensional cousins. Next, I show that the glueball spectrum of the compactified theories is much richer than what have been thought before. In particular, new nonperturbative scales and glueballs emerge in the deep IR regime of the theory. I discuss the spectrum in the context of super Yang-Mills and show that the lightest glueball states fill a chiral supermultiplet with doubly nonperturbative binding energy. I end with possible implications of these findings for the four dimensional gauge theories.
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NSLS-II Friday Lunchtime Seminar Series
"Combining high energy x-ray diffraction techniques with laser-induced fluorescence in operando catalysis"
Presented by Uta Hejral, Lund University, Sweden
Friday, February 2, 2018, 12 pm
NSLS-II Bldg. 743 Rm 156Hosted by: M. Abeykoon, S. Chodankar, B. Ocko, T. Tanabe, J. Thieme
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Condensed-Matter Physics & Materials Science Seminar
"Establishing Jeff =3/2 Ground State in a Lacunar Spinel GaTa4Se8"
Presented by Myung Joon Han, Korea Advanced Institute of Science and Technology (KAIST)
Wednesday, January 31, 2018, 1:30 pm
ISB Bldg. 734 Conf. Rm. 201 (upstairs)Hosted by: Sangkook Choi
In this talk, after briefly introducing the research activities in my group, I will present our recent progress on GaTa4Se8 which is known as a 'paramagnetic Mott' insulator and exhibits superconducting transition under pressure. Its low temperature behaviors found in susceptibility and specific heat measurement have not yet been clearly understood. The important first step to study these intriguing phenomena and the relationship between them is to clarify the nature of its electronic and magnetic property. By using first-principles band structure calculation and resonant inelastic x-ray scattering technique, we show that GaTa4Se8 is a novel 'Jeff=3/2 Mott' insulator in which spin-orbit interaction plays a key role to form a gap together with electronic correlation. The excitations involving the Jeff = 1/2 molecular orbital are absent only at the Ta L2 edge, manifesting the realization of the molecular Jeff = 3/2 ground state in GaTa4Se8. Based on this finding, the possible consequences of the Jeff = 3/2 state will be discussed
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Physics Colloquium
"Fast Radio Bursts"
Presented by Jeff Peterson, Carnegie Mellon University
Tuesday, January 30, 2018, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Andrei Nomerotski
Fast Radio Bursts are millisecond flashes of radio emission that appear randomly across the sky. Since the first report of a burst in 2006, over 20 of these FRBs have been reported. I will review the evidence that FRB sources are at cosmological distances and therefore have inferred brightness temperatures as high as 10^35 K, twenty orders of magnitude higher than gamma ray bursts. The all-sky rate of these events is estimated to be about 5000 per day, so the new HIRAX telescope in South Africa will have the potential to detect 10 events per day. HIRAX will also localize the emission to a single galaxy, so there will be much more information on these mysterious objects in the next few years.
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Joint Nuclear and Particle Physics Seminar
"The SNOLAB Science Programme: cutting-edge science from a deep hole in the ground"
Presented by Nigel Smith, SNOLab
Tuesday, January 30, 2018, 1:30 pm
Small Seminar Room, Bldg. 510Hosted by: Hong Ma
SNOLAB is a deep underground research facility, hosted 2km beneath the surface of the Earth in a working mine at Creighton, near Sudbury, Ontario. Initially the site of the Sudbury Neutrino Observatory, which unambiguously demonstrated flavour-change in neutrinos created in the fusion process of the Sun, SNOLAB now hosts a multi-disciplinary programme. Why do we need to go to such great depths to probe the Universe? This work, and several of the major questions studied in contemporary astro-particle and sub-atomic physics, such as the search for the Galactic dark matter, and studies of neutrinos from supernova, require the ultra-quiet radiation environment afforded by deep underground facilities like SNOLAB. In these facilities, the cosmic-radiation induced backgrounds in the detection systems are reduced to a manageable level, with additional shielding from natural ambient radioactivity and low background construction of detector systems. This talk will provide a review of the science programme at SNOLAB outlining the main science objectives, will review the detectors used for these studies, and outline future plans for the facility.
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Particle Physics Seminar
"A Tale of Two Higgs"
Presented by Baojia Tong, Harvard University
Thursday, January 25, 2018, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Alessandro Tricoli
An enhanced production of double Higgs bosons at the LHC would be a clear sign of beyond Standard Model physics. An ATLAS search is performed for resonant and non-resonant production, where the two Higgs bosons both decay to a pair of Bottom quarks. The analyses use up to ~13/36 fb−1 of p-p collision data collected at 13 TeV. The talk will focus on the boosted analysis, with the resolved analysis introduced as well. Other RunII double Higgs search results and future prospect will also be discussed.
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RIKEN Lunch Seminar
"Exact results on massless 3-flavor QCD through new anomaly matching"
Presented by Yuya Tanizaki, RBRC
Thursday, January 25, 2018, 12:30 pm
Building 510, Room 2-160Hosted by: Enrico Rinaldi
Recently, we find a new 't Hooft anomaly of massless 3-flavor QCD, and it turns out to be useful for constraining the possible chiral symmetry breaking at finite density and zero temperature. We briefly review the anomaly matching by a toy example, and show that massless 3-flavor QCD has an 't Hooft anomaly related to ''center'' and discrete axial symmetries. We also discuss its consequences on the expectation value of the special symmetry-twisting operator, which gives the phase diagram of so-called Z(3)-QCD.
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Physics Colloquium
"Cold Atom Sensing: Gravity, Tomography, and Gyroscopes"
Presented by Steve Libby, LLNL
Tuesday, January 23, 2018, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Rob Pisarski
The ability to use lasers to cool atoms to micro-kelvin temperatures and to subsequently control their quantum mechanical behavior1 has led to the development of exquisitely precise 'quantum' sensors.2 Applications of these sensors include the measurement of local gravitational anomalies to unprecedented accuracy and very accurate, highly stable gyroscopes. Our LLNL - AOSense, Inc. collaboration is pursuing diverse applications of these sensors that directly exploit their extraordinary scale factor stability, low noise and bias drift characteristics. These applications include shielded threat detection in passing vehicles, emergency response, and treaty verification, all of which require rapid, passive methods to determine hidden mass configurations precisely and/or verify the masses present in containers. Such dense, localized objects can in principle be discovered and accurately measured by their effect on the local gravitational field.3 Furthermore, near field measurements of these gravitational perturbations from multiple vantage points allow for a kind of gravitational 'tomography,' leading to the real-time determination of the hidden mass distribution. Additionally, we are interested in the potential of atom interferometer Sagnac gyroscopes to do accurate 'dead reckoning' navigation without the aid of GPS.4 After reviewing the physics of atom interferometry in atomic fountain-Mach-Zehnder and Sagnac configurations, I will describe the development of a 'gravity tomography' signal analysis system for vehicle portals, including the optimal synthesis of the gravitational sensor signals with complementary radiation detection.
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Nuclear Physics Seminar
"Probing the Quark-Gluon Plasma with Open Heavy Flavor Mesons using CMS detector"
Presented by Professor Yen-Jie Lee, MIT
Tuesday, January 23, 2018, 11 am
Small Seminar Room, Bldg. 510Hosted by: Rongrong Ma
The measurements of heavy flavor production and collective flow could be used to extract the properties of the high-density QCD medium created in heavy-ion collisions as heavy quarks are sensitive to the transport properties of the medium and may interact with the QCD matter differently from light quarks. In particular, the comparison between the nuclear modification factors (RAA) of light- and heavy-flavor particles provides insights into the expected flavor dependence of in-medium parton energy loss. Furthermore, azimuthal anisotropy coefficient (vn) of heavy-flavor particles provide information about the degree of the thermalization of the bulk medium at low pT, and unique information about the path length dependence of heavy quark energy loss at high pT. Recently, a comprehensive heavy flavor program is established in the CMS collaboration including the detection of charm and beauty meson. Using the large statistics heavy ion data samples collected during the 2015 and 2016 LHC runs, high precision open charm and beauty measurements are performed with CMS over a wide transverse momentum range. This allows us to set an important milestone in our understanding of the interactions between heavy quarks and the medium. In this talk, the most recent results of v2 and v3 of D0 mesons in PbPb collisions at 5.02 TeV are presented and compared to the same results for charged hadrons at the same energy. Latest results on nuclear modification factor of D, non-prompt J/psi and B mesons in PbPb collisions are also presented.
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Condensed-Matter Physics & Materials Science Seminar
"Spin-orbit coupling and electronic correlations in Hund's metals: Sr2RuO4"
Presented by Minjae Kim, École Polytechnique, France
Monday, January 22, 2018, 1:30 pm
ISB Bldg. 734 Conf. Rm. 201 (upstairs)Hosted by: Gabi Kotliar
We investigate the interplay of spin-orbit coupling (SOC) and Hund's rule coupling driven electronic correlations in Sr2RuO4 using dynamical mean-field theory. We find that the orbital diagonal components of the dynamical electronic correlations are unaffected by the SOC, which validates the concept of a Hund's metal in the presence of SOC. In contrast, SOC itself is enhanced by approximately a factor of two by electronic correlations. We introduce the concept of an energy dependent quasiparticle SOC, which is found to be essential in accounting simultaneously for: (i) the Fermi surface (ii) the low-energy dispersion of quasiparticles and (iii) the splitting between bands at higher binding energy. Our calculations are in good agreement with available experimental data. References: [1-4] [1] C. Veenstra et al., Physical Review Letters 112, 127002 (2014) [2] M. Haverkort et al., Physical Review Letters 101, 026406 (2008) [3] J. Mravlje et al., Physical Review Letters 106, 096401 (2011) [4] M. Kim et al., arXiv preprint arXiv:1707.02462 (2017)
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Nuclear Theory/RIKEN Seminar
"Semi-inclusive jet cross sections within SCET"
Presented by Felix Ringer, LBL
Friday, January 19, 2018, 2 pm
Small Seminar Room, Bldg. 510We review the de nition of semi-inclusive jet functions within Soft Collinear E ective Theory (SCET) and their application to inclusive jet cross sections. We consider the fully inclusive production cross section of jets as well as several jet substructure observables in proton-proton collisions relevant for the LHC and RHIC. The corresponding semi-inclusive jet functions satisfy renormalization group (RG) equations which take the form of standard timelike DGLAP evolution equations, analogous to collinear fragmentation functions. By solving these RG equations, the resummation of potentially large single logarithms n s lnn R can be achieved. We present numerical results at NLO+NLLR accuracy and compare to the available data.
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Particle Physics Seminar
"Search for the Higgs boson produced in association with top quarks and decaying into a b quark pair with the ATLAS detector at LHC"
Presented by Thomas Calvet, Stony Brook University
Thursday, January 18, 2018, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Alessandro Tricoli
The discovery of a particle compatible with the Standard Model (SM) Higgs boson in 2012 by the ATLAS and CMS collaborations at LHC is a milestone in particle physics. In order to assess whether or not this Higgs boson belongs to the SM, it is necessary to measure its properties, in particular its coupling to the top quark (the strongest Yukawa coupling in the SM). The associated production of a Higgs boson with a pair of top quarks, ttH gives the most favorable direct access to the top quark Yukawa coupling and is accessible for the first time in LHC Run 2. A search for the ttH production with the Higgs boson decaying into a b quark pair, ttH(bb), will be presented. It uses the 36.1 fb^-1 of data recorded by the ATLAS detector in 2015 and 2016. The main limitation to the search of ttH(bb) events is the tt+jets background and its systematic uncertainties. To achieve sufficient sensitivity, this complex analysis relies on several advanced tools to separate the leading background tt+jets from the signal, and to extract both of these processes from data (multi-variate analysis, profile likelihood fit, etc.). All these key aspects of the analysis will be discussed. The combination of the ttH(bb) channel with the other decay modes is necessary to improve the sensitivity to the ttH production mode. This combination leads to 4.2 sigma evidence of the ttH production and will be also presented.
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RIKEN Lunch Seminar
"World-line Approach to Chiral Kinetic Theory and the Chiral Magnetic Effect"
Presented by Niklas Mueller, BNL
Thursday, January 18, 2018, 12:30 pm
Building 510, Room 1-224Hosted by: Enrico Rinaldi
Experimental searches for messengers of CP- and P- odd phenomena at RHIC and LHC have attracted much interest and are a prime motivation for significant theoretical effort: Anomalous and topological effects receive important contributions from the pre-equilibrium phase of a collision and an interesting question of phenomenological relevance is how the chiral imbalance generated at early times persists through a fluctuating background of sphalerons in addition to other "non-anomalous" interactions with the QGP. To address this question, we construct a relativistic chiral kinetic theory using the world-line formulation of quantum field theory. We outline how Berry's phase arises in this framework, and how its effects can be clearly distinguished from those arising from the chiral anomaly. We further outline how this framework can be matched to classical statistical simulations at early times and to anomalous chiral hydrodynamics at late times.
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Environmental & Climate Sciences Department Seminar
"Understanding the Structure and Dynamics of Long-Duration Floods using Physics Informed Bayesian Multilevel Models"
Presented by Naresh Devineni, CUNY
Thursday, January 18, 2018, 11 am
Conference Room Bldg 815EHosted by: Bob McGraw
Long duration floods cause substantial damage and prolonged interruptions to water resource facilities, critical infrastructure, and regional economic development. We present a novel physics-based model for inference of such floods with a deeper understanding of dynamically integrated nexus of land surface wetness, effective atmospheric blocking/circulation, and moisture transport/release mechanism. Diagnostic results indicate that the flood duration is varying in proportion to the antecedent flow condition which itself is a function of the available moisture in the air, the persistency in atmospheric pressure blocking, convergence of water vapor, and the effectiveness of divergent wind to condense the aforesaid atmospheric water vapor into liquid precipitation. A physics-based Bayesian inference model is developed that considers the complex interactions between moisture transport, synoptic-to-large-scale atmospheric blocking/circulation pattern, and the antecedent wetness condition in the basin. We explain more than 80% variations in flood duration with a high success rate on the occurrence of long duration floods. Our findings underline that the synergy between a large persistent low-pressure blocking system and a higher rate of divergent wind often triggers a long duration flood, even in the presence of moderate moisture supply in the atmosphere. This condition in turn causes an extremely long duration flood if the basin-wide surface wetness prior to the flood event was already high.
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Condensed-Matter Physics & Materials Science Seminar
""In situ characterization of the phase behavior of metal oxides at extreme conditions""
Presented by Leighanne Gallington, Argonne National Laboratory
Wednesday, January 17, 2018, 1:30 pm
ISB Bldg. 734 Conf. Room 201 (upstairs)Hosted by: Ian Robinson
In situ characterization of the phase behavior of materials in the lab is complicated by the difficulty of designing compatible sample environments as well as the long time scales required to acquire diffraction data with sufficient counting statistics for crystallographic analyses. The high energy x-rays available at synchrotron sources allow for penetration of most sample environments, while high flux allows for rapid acquisition of diffraction patterns, thereby allowing construction of detailed phase diagrams. Low and negative thermal expansion (NTE) materials have been studied extensively, as they can potentially be used to create composites with finely controlled thermal expansion characteristics, improved resistance to thermal shock, and a broader range of operating temperatures.1-4 While the thermal expansion behavior of the NTE materials ZrW2O8 and HfW2O8 was well-described at ambient pressures,4-6 knowledge of the effects of stress on their thermal expansion was limited.7 In situ synchrotron powder diffraction was utilized to explore the role of orientational disorder in determining both the phase behavior and the thermoelastic properties of these materials. An especially designed pressure cell allowed for simultaneous sampling of temperatures up to 513 K and pressures up to 414 MPa.8 Reversible compression-induced orientational disordering of MO4 tetrahedra occurred concomitantly with elastic softening on heating and enhanced negative thermal expansion upon compression in ZrW2O8 and HfW2O8, but only in the ordered phase.9, 10 In light of the comparatively recent nuclear disaster in Fukushima, understanding interactions and phase behavior in nuclear fuels under severe accident conditions is of paramount interest. While diffraction measurements have been performed on materials recovered from melts of corium (UO2-ZrO2), there is a lack of in situ characterization of this material at elevated temperatures. Achieving the extreme temperatures required
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Particle Physics Seminar
"Improved Point Source Detection in Crowded Fields using Probabilistic Cataloguing"
Presented by Stephen Portillo, Harvard University
Tuesday, January 16, 2018, 11 am
Small Seminar Room, Bldg. 510Hosted by: Erin Sheldon
Cataloging is challenging in crowded fields because sources are extremely covariant with their neighbors and blending makes even the number of sources ambiguous. We present the first optical probabilistic stellar catalogue, cataloguing a crowded (~0.1 sources per pixel) SDSS r band image from M2. We show that our probabilistic catalogue goes more than a magnitude deeper than the DAOPHOT while having a lower false discovery rate brighter than 20th magnitude. We detail our efforts to speed up the method and extend it to galaxies, making probabilistic cataloguing applicable to the data that will be collected in the LSST era.
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Condensed-Matter Physics & Materials Science Seminar
"Singular density fluctuations in the strange metal phase of Bi2Sr2CaCu2O8+x observed with momentum-resolved EELS (M-EELS)"
Presented by Peter Abbamonte, University of Illinois at Urbana Champaign
Friday, January 12, 2018, 11 am
ISB Bldg. 734, Conf. Room 201 (upstairs)Hosted by: Peter D. Johnson
High-temperature superconductivity arises out of an anomalous normal state commonly referred to as a "bad" or "strange" metal, since it lacks the usual signatures of electron quasiparticles. In ordinary metals, such quasiparticles manifest as propagating collective modes encoded in the dynamic charge susceptibility ??(q,?), which describes the response of the system to applied fields. However, the analogous collective modes of a strange metal are currently unknown. Here, we present the first measurement of ??(q,?) for a prototypical strange metal, Bi2.1Sr1.9CaCu2O8+x (BSCCO), using momentum-resolved inelastic electron scattering (M-EELS). We discover a surprising energy- and momentum-independent continuum of fluctuations extending up to 1 eV, at odds with the dispersive plasmons expected in normal metals. This spectrum is found to be temperature-independent across the superconducting phase transition at optimal doping. Tuning the composition to overdoping, where a crossover to Fermi liquid behavior is expected, this momentum-independent continuum is found to persist, though a 0.5 eV gap-like feature now emerges at low temperature. Our results indicate that the phenomenon underlying the strange metal is a singular form a charge dynamics of a new kind, that does not fit into any known picture of quantum critical scaling.
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Condensed-Matter Physics & Materials Science Seminar
"Bose condensation of excitons in TiSe2"
Presented by Peter Abbamonte, University of Illinois at Urbana–Champaign
Thursday, January 11, 2018, 1:30 pm
ISB Bldg. 734, Conf. Room 201 (upstairs)Hosted by: Peter D. Johnson
Bose condensation has shaped our understanding of macroscopic quantum phenomena, having been realized in superconductors, atomic gases, and liquid helium. Excitons are bosons that have been predicted to condense into either a superfluid or an insulating electronic crystal. But definitive evidence for a thermodynamically stable exciton condensate has never been achieved. In this talk I will describe our use of momentum-resolved electron energy-loss spectroscopy (M-EELS) to study the valence plasmon in the transition metal dichalcogenide semimetal, 1T-TiSe2. Near the phase transition temperature, TC = 190 K, the plasmon energy falls to zero at nonzero momentum, indicating dynamical slowing down of plasma fluctuations and crystallization of the valence electrons into an exciton condensate. At low temperature, the plasmon evolves into an amplitude mode of this electronic crystal. Our study represents the first observation of a soft plasmon in any material, the first definitive evidence for exciton condensation in a three-dimensional solid, and the discovery of a new form of matter, "excitonium."
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RIKEN Lunch Seminar
"Three-dimensional gauge theories using lattice regularization"
Presented by Nikhil Karthik
Thursday, January 11, 2018, 12:30 pm
Building 510, Room 2-160Hosted by: Yuya Tanizaki
Three-dimensional gauge theories with massless fermions provide a simple yet non-perturbative setting to understand why QCD has a scale, and also provide effective descriptions of condensed matter systems. Along these lines, I will present results on infra-red scaling and scale-breaking in three-dimensional QED, QCD and large-Nc theories. I will also present some preliminary results on three-dimensional QED with one flavor of fermion regulated with and without parity anomaly.
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Condensed-Matter Physics & Materials Science Seminar
""Photoemission studies of the electronic properties of rare-earth intermetallics and oxide interface""
Presented by Alla Chikina, Paul Scherrer Institute, Switzerland
Monday, January 8, 2018, 3 pm
ISB Bldg. 734 Seminar Room 201 (upstairs)Hosted by: Cedomir Petrovic
Longer than 70 years solid state research has been focused on the study of materials with strong electron correlations due to their remarkable electronic and magnetic properties. In such systems, the average energy of the Coulomb interaction is greater or comparable to its kinetic energy and electrons tend to be localized. This localization is strong enough that electrons can be considered in the framework of the atomic approach. Interaction with itinerant electrons makes the interpretation of their physical properties more complicated. A typical example of a strongly-correlated system contains transition and rare earth (RE) elements. Here, I present both theoretical and experimental insight into the itinerant-localized electron interaction in rare-earth 122 silicides (RERh2Si2). The properties of RERh2Si2 change from the heavy-fermion behavior in YbRh2Si2 up to well-pronounced magnetic properties in EuRh2Si2 and GdRh2Si2. The competition between the Kondo effect and the magnetic RKKY interactions determines the properties of a large class of materials which have localized 4f magnetic moments coupled to itinerant valence electrons. The strong electron correlations, also well known in the transition metal oxides, rise up their remarkable functional and magnetic properties. It gives a route in a manipulation of electron, spin, orbital and lattice degrees of freedom for novel electronic and spintronic devices based on oxide interfaces. An important role in the electronic and magnetic properties of this interface is played by oxygen vacancies which form a dichotomic electron system where strongly correlated localized electrons in the in-gap states (IGSs) coexist with less correlated ones constituting the mobile two-dimensional electron system (2DES). On the example of the interface between LaAlO3 and SrTiO3 we consider a complex band ordering in the dichotomic LAO/STO electron system that goes beyond the conventional eg vs t2g picture.
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Nuclear Theory Seminar
"Thermodynamics of string bits"
Presented by Sourav Raha, University of Florida
Monday, January 8, 2018, 11 am
Large Seminar Room, Bldg. 510Hosted by: Andrey Tarasov
We study the Hagedorn transition in the singlet sector of the simplest super-string bit model in the tensionless limit. The gauge group of our model is SU(N) and this transition takes place when N is infinite. We use orthogonality of group characters in order to calculate the partition function. At the Hagedorn temperature there is a change in the distribution of parameters that maximize this partition function. We conclude by devising a field-theoretic interpretation of the this phenomenon.
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Nuclear Theory/RIKEN Seminar
"Thermodynamics of string bits"
Presented by Sourav Raha, University of Florida
Friday, January 5, 2018, 2 pm
Small Seminar Room, Bldg. 510We study the Hagedorn transition in the singlet sector of the simplest super-string bit model in the tensionless limit. The gauge group of our model is SU(N) and this transition takes place when N is infinite. We use orthogonality of group characters in order to calculate the partition function. At the Hagedorn temperature there is a change in the distribution of parameters that maximize this partition function. We conclude by devising a field-theoretic interpretation of the this phenomenon.
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Condensed-Matter Physics & Materials Science Seminar
"Illuminating rationally engineered complex oxides"
Presented by Derek Meyers, BNL
Friday, January 5, 2018, 1:30 pm
ISB Bldg. 734 Conf. Rm. 201 (upstairs)Hosted by: Mark Dean
Advances in unit cell scale synthesis have unlocked the ability to create artificial materials at the interface of complex oxides. This opens the door to the rational design of materials properties. To explore the spin, charge, and orbital character of these synthetic materials, resonant x-ray scattering techniques are utilized which unveil their long-range ordering and low energy excitations. In this talk, we will explore several recent examples of this new methodology and provide an outlook on the future of this emergent field.
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Condensed-Matter Physics & Materials Science Seminar
"Spin fluctuations in 122 transition metal arsenides measured using inelastic neutron scattering technique"
Presented by Aashish Sapkota, Ames Laboratory
Thursday, December 21, 2017, 1:30 pm
ISB Bldg. 734 Conf. Rm. 201 (upstairs)Hosted by: John Tranquada
122 transition metal compounds with ThCr2Si2-type structure have been extensively studied because of their wide range of interesting physical properties like superconductivity, valence fluctuations, various magnetic ground states, etc. A subset (ATM2Pn2) of this class consisting of alkaline earth metals (A), 3d transition metals (TM) and pnictogen (Pn) attracted significant interest after discovery of an unconventional superconductivity in 122 iron arsenide compounds. In 122 iron arsenide superconductors, magnetism is in close proximity to the superconductivity and the spin fluctuations are considered as a key component for the pairing mechanism for superconductivity. These properties as well as the wide range of magnetic ground states, found in ATM2As2, motivated a detail studies of the magnetism in these compounds and neutron scattering technique has been extensively used for the study. In this seminar, I will discuss our results of inelastic neutron scattering measurements of the spin fluctuations in two compounds [CaCo1.86As2 and Ca(Fe1-xCox)2As2] of ATM2Pn2 class. First, I will discuss extremely extended spin fluctuations along two directions of reciprocal space in CaCo1.86As2, which shows A-type antiferromagnetic ground states. The result suggests that CaCo1.86As2 is highly-frustrated and is a unique example of highly-frustrated square-lattice system. Next, I will discuss the evolution of the spin fluctuations in Co-doped CaFe2As2 and compare it to that of Co-doped BaFe2As2. In this part, I will also discuss a peculiar suppression of the spin fluctuations with temperature observed in Ca(Fe1-xCox)2As2, x = 0.030 compound, which shows superconducting ground state.
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Nuclear Theory/RIKEN Seminar
"Simultaneous extraction of spin-dependent parton distributions"
Presented by Nobuo Sato, Jlab/University of Connecticut
Friday, December 15, 2017, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Andrey Tarasov
In this talk, I will present a recent global QCD analysis of spin-dependent PDFs and FFs using a MC methodology by the Jefferson Angular Momentum collaboration (JAM).
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HET Seminar
"Searching for Ultralight Particles with Black Holes and Gravitational Waves"
Presented by Masha Baryakhtar, Perimeter Inst. Theor. Phys.
Wednesday, December 13, 2017, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Christopher Murphy
The LIGO detection of gravitational waves has opened a new window on the universe. I will discuss how the process of superradiance, combined with gravitational wave measurements, makes black holes into nature's laboratories to search for new light bosons, from axions to dark photons. When a bosonic particle's Compton wavelength is comparable to the horizon size of a black hole, superradiance of these bosons into `hydrogenic' bound states extracts energy and angular momentum from the black hole. The occupation number of the levels grows exponentially and the black hole spins down. One candidate for such an ultralight boson is the QCD axion with decay constant above the GUT scale. Current black hole spin measurements disfavor a factor of 30 (400) in axion (vector) mass; future measurements can provide evidence of a new boson. Particles transitioning between levels and annihilating to gravitons may produce thousands of monochromatic gravitational wave signals, and turn LIGO into a particle detector.
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Physics Colloquium
"The "self-stirred" genome: Bulk and surface dynamics of the chromatin globule"
Presented by Alexandra Zidovska, New York University
Tuesday, December 12, 2017, 3:30 pm
Large Seminar Room, Bldg. 510Chromatin structure and dynamics control all aspects of DNA biology yet are poorly understood. In interphase, time between two cell divisions, chromatin fills the cell nucleus in its minimally condensed polymeric state. Chromatin serves as substrate to a number of biological processes, e.g. gene expression and DNA replication, which require it to become locally restructured. These are energy-consuming processes giving rise to nonequilibrium dynamics. Chromatin dynamics has been traditionally studied by imaging of fluorescently labeled nuclear proteins and single DNA-sites, thus focusing only on a small number of tracer particles. Recently, we developed an approach, displacement correlation spectroscopy (DCS) based on time-resolved image correlation analysis, to map chromatin dynamics simultaneously across the whole nucleus in cultured human cells [1]. DCS revealed that chromatin movement was coherent across large regions (4–5μm) for several seconds. Regions of coherent motion extended beyond the boundaries of single-chromosome territories, suggesting elastic coupling of motion over length scales much larger than those of genes [1]. These largescale, coupled motions were ATP-dependent and unidirectional for several seconds. Following these observations, we developed a hydrodynamic theory of active chromatin dynamics, using the two-fluid model and describing the content of cell nucleus as a chromatin solution, which is subject to both passive thermal fluctuations and active (ATP-consuming) scalar and vector events [2]. In this work we continue in our efforts to elucidate the mechanism and function of the chromatin dynamics in interphase. We investigate the chromatin interactions with the nuclear envelope and compare the surface dynamics of the chromatin globule with its bulk dynamics [3]. Furthermore, we explore the rheology of the chromatin inside the cell nucleus using the native subnuclear structures [4]. [1] Zidovska A, Weitz DA, Mitchi
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Particle Physics Seminar
"A Unified Program of Argon Dark Matter Searches: DarkSide-20k and The Global Argon Dark Matter Collaboration"
Presented by Cristiano Galbiati, Princeton University
Monday, December 11, 2017, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Alessandro Tricoli
: Experimenters from four different argon dark matter searches have joined their forces in the the "Global Argon Dark Matter Collaboration" to carry out a unified program for dark matter direct detection. The participants are researchers currently working on the ArDM experiment at LSC; on the DarkSide-50 experiment at LNGS; on the DEAP-3600 experiment at SNOLab; and on the MiniCLEAN experiment at SNOLab. In 2015/2016 The DarkSide-50 experiment at LNGS produced two zero-background science results, along with a comparison of the results obtained with both atmospheric and underground argon fills, demonstrating the ability of large experiments to eliminate background from betas/gammas at the tens of tonne-year exposure. The DEAP-3600 experiment at SNOLAB is the first tonne-scale experiment to achieve both stable operations and an extended physics run. DEAP-3600 has been collecting physics data with over 3 tonnes of argon since late 2016 and published its first results in 2017. Researchers from the four experiments will jointly carry out as the single next step at the scale of a few tens of tonnes the DarkSide-20k experiment. DarkSide-20k was approved in 2017 by the Italian INFN, by the host laboratory LNGS, and by the US NSF. DarkSide-20k is also officially and jointly supported by the three underground laboratories LNGS, LSC, and SNOLab. DarkSide-20k is a 20-tonne fiducial volume dual-phase TPC to be operated at LNGS with an underground argon fill, designed to collect an exposure of 100 tonne×years, completely free of neutron-induced nuclear recoil background and all electron recoil background. DarkSide-20k is set to start operating by 2021 and will have sensitivity to WIMP-nucleon spin-independent cross sections of 1.2 × 10−47 cm2 for WIMPs of 1 TeV/c2 mass, to be achieved during a 5 year run. An extended 10 year run could produce an exposure of 200 tonne×years, with sensitivity for the cross-section of 7.4 × 10&min
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Particle Physics Seminar
"Machine Learning Analysis of Ising Worms"
Presented by Sam Foreman, University of Iowa
Thursday, December 7, 2017, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Chao Zhang
Motivated by recent results demonstrating the applicability of machine learning techniques to quantum spin systems, we explore an application of the worm algorithm to the two dimensional Ising model. We begin by presenting the high temperature expansion of the Ising model, which is used to generate equilibrium configurations of "worms" represented as two¬dimensional greyscale images. From these configurations, we are then able to calculate physical quantities of interest. In particular, we are able to identify the logarithmic divergence of the specific heat at the critical temperature. We then propose a complementary approach using machine learning techniques (in particular, principal component analysis, (PCA)) which also successfully identifies the divergent behavior near criticality. Finally, we investigate the behavior of the previously mentioned concepts under a renormalization group coarse¬graining procedure, and present ideas for future research.
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RIKEN Lunch Seminar
"Pushing the boundaries of relativistic fluid dynamics"
Presented by Jorge Noronha
Thursday, December 7, 2017, 12:30 pm
Building 510, Room 2-160Hosted by: Enrico Rinaldi
For nearly a century, dissipative effects have been included in fluid dynamics using gradients of macroscopic quantities such as the temperature and fluid velocity. Recently, results from heavy ion collision experiments and explicit model calculations have pushed the boundaries of relativistic fluid dynamics towards the far-from-equilibrium regime. In this talk I will present calculations of the large order behavior of the gradient expansion, both in kinetic theory and in holography, which have demonstrated that this series has zero radius of convergence. I will discuss the role played by novel non-equilibrium attractor solutions in determining the emergence of fluid dynamic behavior in many-body systems under extreme conditions.
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Condensed-Matter Physics & Materials Science Seminar
"Examples of translational research using thermoelectric oxides"
Presented by Ryoji Funahashi, National Institute of Advanced Industrial Science & Technology, Japan
Wednesday, December 6, 2017, 3 pm
Conference Room, Building 480Hosted by: Qiang Li
We have been relishing a lot of affluence thanks to energy. Fossil energy provides us fun to drive, warmth to escape from cold, brightness of illumination, etc. However consumption of the fossil fuel produces CO2. The amount of CO2 emission will increase with increasing consumption of fossil energy, gas, oil, and coal year by year. The average of total utilizing efficiency of the primary energy is as low as 30 %, with 70 % exhausted to the air as waste heat. It is clear that improved efficiencies of energy conversion systems could have a significant impact on energy consumption and carbon dioxide emission rate. Where a large sum of heat is localized, mechanical conversion systems can be used to generate electricity. However, most sources of waste heat are widely dispersed. Although technologies of storage and transport of such the dilute heat energy have been developed, most waste heat can't be used effectively. Electricity is a convenient form of energy that is easily transported, redirected, and stored, thus there are a number of advantages to the conversion of waste heat emitted from our living and industrial activities to electricity. Thermoelectric conversion is paid attention as the strongest candidate to generate electricity from dilute waste heat. Oxide materials are considered to be promising ones because of their durability against high temperature, low cost for producing etc. The misfit CoO2 compounds show high thermoelectric efficiency at high temperature in air. Thermoelectric modules using p-type Ca3Co4O9, one of the CoO2 compounds and n-type CaMnO3 have been produced [1, 2]. The maximum power density against area of the substrate of the module reaches 4.3 kW/m2 at 973 K of the heat source temperature [3]. Portable power generation units composed of an oxide thermoelectric module. Water circulation and batteries for air cooling are unnecessary for thermoelectric conversion. The units can generate 2-5 W using heat energy with temperature of 300-8
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Physics Colloquium
"Thinking inside the box - hadron resonances in QCD"
Presented by Jozef Dudek, JLab
Tuesday, December 5, 2017, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Rob Pisarski
I will describe how we can make use of the finite box in which lattice QCD calculations are performed to learn something about hadron scattering amplitudes from first principles. These amplitudes contain information about the resonance structure of QCD and hence the spectrum of excited mesons and baryons. I'll present the results of recent calculations in which the lightest scalar, vector and tensor mesons have been studied.
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Nuclear Theory/RIKEN seminar
"Medium modification of jet and jet-induced medium excitation"
Presented by Shanshan Cao, Wayne State University
Friday, December 1, 2017, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Chun Shen
A coupled linear Boltzmann transport and hydrodynamics model (CoLBT-hydro) is developed for concurrent simulation of jet propagation and hydrodynamic evolution in high-energy nuclear collisions. Diverse microscopic scattering processes (elastic and inelastic) are incorporated for parton showers, and both massive and massless partons are calculated on the same footing. Energy deposition from jets into nuclear matter is treated as source term of hydrodynamic evolution. Within this CoLBT-hydro model, nuclear modification of heavy and light flavor hadrons are simultaneously described. Evidence of jet-induced medium excitation is explored with photon-triggered jets, where significant enhancement of soft hadron production is found due to energy deposition from jets.
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Particle Physics Seminar
"The strong CP-problem and axion dark matter searches"
Presented by Yannis Semertzidis, KAIST and IBS
Monday, November 27, 2017, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Chao Zhang
The strong CP-problem, i.e. why is the neutron EDM experimental limit is at least ten orders of magnitude lower than expected from the theory of QCD is one of the mysteries in physics today. Peccei and Quinn came up with a solution to the strong CP-problem at the expense of requiring an extra pseudo-scalar particle, the axion. It turns out, the axion at a certain mass range is also an ideal dark matter candidate and it can be detected via its conversion to microwave photons in the presence of a strong magnetic field. IBS/CAPP in South Korea, the center for axion and precision physics research of the institute for basic science, was established to elucidate the strong CP-problem and in particular the axion dark matter mystery. I'm going to give an overview of the history of axion dark matter searches, the present status and the plans for answering whether or not axions are a significant part of the dark matter in our galaxy.
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Physics Colloquium
"Numerical Relativity in the Multimessenger Era"
Presented by Manuela Campanelli, Rochester Institute of Technology
Tuesday, November 21, 2017, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Peter Petreczky
The recent discovery of gravitational waves by Advanced LIGO ushered in a new kind of astronomy, one potentially integrating its findings with those obtained from electromagnetic and/or neutrino observations. Multi-messenger astronomy promises to revolutionize our understanding of the universe by providing dramatically contrasting views of the same objects. To understand this unprecedented wealth of observational evidence, computer intensive theoretical calculations of the Einstein field equations, coupled with the equations of magneto-hydrodynamics, are required in order to link data with underlying physics. In this talk, I will provide a review on the recent progress in this exciting field of computational astrophysics. With Advanced LIGO now fully operational and the detection of additional gravitational wave events imminent, we expect that there will be a surge in the number of researchers interested in performing simulations of compact binary mergers.
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Nuclear Theory/RIKEN Seminar
"Higher-order corrections to jet quenching"
Presented by Yacine Mehtar-Tani, University of Washington
Friday, November 17, 2017, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Chun Shen
The phenomenon of jet quenching in ultra-relativistic heavy ion collisions reveals to effect of substantial finial state interactions which cause QCD jets to lose energy to the quark-gluon plasma (QGP), mainly by induced gluon radiation. In standard analytic approaches to energy loss, jets are approximated by single partons and thus higher-order effects in the strong coupling constant are neglected. This may prove insufficient to reliably extract QGP properties at high pT, where a significant jet suppression was recently reported by the ATLAS collaboration in PbPb collisions at the LHC. In this work we explore higher-order corrections to the inclusive jet spectrum which may be sizable owing to the fact that the probability for a highly virtual parton to split in the medium increases with the jet pT. As the effective number of jet constituents increases, jets are expected to lose more energy than a single color charge. This translates into large logarithmic enhancements of higher-orders in the perturbative series, that need to be resummed. As a result we obtain a Sudakov-like suppression factor which we investigate in the leading logarithmic approximation. We note, however, that the phase space for higher-order corrections is mitigated by coherence effects that relate to the fact that, below a characteristic angular scale, the medium does not resolve the inner jet structure. In this case, the jet lose energy coherently as a single color charge, namely, the primary parton.
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Condensed-Matter Physics & Materials Science Seminar
"Complementary response of static spin-stripe order and superconductivity to non-magnetic impurities and pressure in cuprates"
Presented by Zurab Guguchia, Columbia University
Thursday, November 16, 2017, 1:30 pm
ISB Bldg. 734, Conference Room 201 (upstairs)Hosted by: Emil Bozin
Cuprate high-temperature superconductors (HTSs) have complex phase diagrams with multiple competing ordered phases. Understanding to which degree charge, spin, and superconducting orders compete or coexist is paramount for elucidating the microscopic pairing mechanism in the cuprate HTSs. In this talk, i will report some novel results of muonspin rotation (μSR), neutron Scattering and magnetization experiments on non-magnetic Zn impurity and hydrostatic pressure effects on the static spin-stripe order and superconductivity in the La214 cuprates [1,2]. Namely, in La2−xBaxCu1−yZnyO4 (0.11 ≤ x ≤ 0.17) and La1.48Nd0.4Sr0.12Cu1−yZnyO4. Remarkably, it was found that in these systems the spin-stripe ordering temperature Tso decreases linearly with Zn doping y and disappears at y ≈ 4 % , demonstrating the extreme sensitivity of static spin-stripe order to impurities within a CuO2 plane. Moreover, Tso is suppressed in the same manner as the superconducting transition temperature Tc by Zn impurities. We also observed the same pressure evolution of both Tc and Tso in La2−xBaxCuO4, while there is an antagonistic pressure evolution of magnetic volume fraction and superfluid density [1,2,3]. These results indicate that static spin-stripe order and SC pairing correlations develop in a cooperative fashion in La214 cuprates. In other words, the existence of the stripe order requires intertwining with the SC pairing correlations, such as occurs in the proposed pair-density wave (PDW) state [4]. [1] Z. Guguchia et. al., Phys. Rev. B 94, 214511 (2016). [2] Z. Guguchia et. al., Phys. Rev. Lett. 119, 087002 (2017). [3] Z. Guguchia et. al., Phys. Rev. Lett. 113, 057002 (2014). [4] E. Fradkin, S.A. Kivelson, and J.M. Tranquada, Rev. Mod. Phys. 87, 457 (2015).
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RIKEN Lunch Seminar
"QCD from gluon, quark, and meson correlators"
Presented by Mario Mitter, BNL
Thursday, November 16, 2017, 12:30 pm
Building 510, Room 2-160Hosted by: Hiromichi Nishimura
We present non-perturbative first-principle results for quark-, gluon- and meson 1PI correlation functions of two-flavour Landau-gauge QCD in the vacuum and Yang-Mills theory at finite temperature. They are obtained by solving their Functional Renormalisation Group equations in a systematic vertex expansion, aiming at apparent convergence within a self-consistent approximation scheme. These correlation functions carry the full information about the theory and their connection to physical observables is discussed. The presented calculations represent a crucial prerequisite for quantitative first-principle studies of QCD and its phase diagram within this framework. In particular, we have computed the ghost, quark and scalar-pseudoscalar meson propagators, as well as gluon, ghost-gluon, quark-gluon, quark, quark-meson, and meson interactions and the magnetic and electric components of the gluon propagator, and the three- and four-gluon vertices. Our results stress the crucial importance of the quantitatively correct running of different vertices in the semi-perturbative regime for describing the phenomena and scales of confinement and spontaneous chiral symmetry breaking without phenomenological input. We confront our results for the correlators with lattice simulations and compare our Debye mass to hard thermal loop perturbation theory. Finally, applications to "QCD-enhanced" low-energy effective models of QCD are discussed.
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Physics Colloquium
""The muon anomalous magnetic moment — A precision test of the standard model""
Presented by Christoph Lehner, BNL
Tuesday, November 14, 2017, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Robert Pisarski
The anomalous magnetic moment of the muon is one of the most precisely determined quantities in particle physics. It is currently known both experimentally and from theory to approximately 1/2 parts per million. Interestingly, there is an approximate 3—4 sigma tension between theory computation and the experimental value (BNL E821) which may hint at new physics beyond the standard model of particle physics. In this talk, I review the current status of a soon-expected improved experimental measurement (FNAL E989) and recent rapid progress in reducing the uncertainty of the standard model theory computation.
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Nuclear Physics Seminar
"Fermilab E-906/SeaQuest: A novel nucleon structure laboratory"
Presented by Bryan Ramson, University of Michigan
Tuesday, November 14, 2017, 11 am
Small Seminar Room, Bldg. 510Hosted by: Oleg Eyser
SeaQuest is the latest iteration in a series of Fermilab experiments designed to probe nucleon structure using the Drell-Yan process. The most recent ancestor of SeaQuest, E866/NuSea, used the Drell-Yan process to provide the most comprehensive observations of the light-quark flavor asymmetry to date, which suggested significant non-pertubative effects in the nucleon sea. Other measurements concerning cold nuclear matter, J/Psi production, and Drell-Yan angular distributions were conducted as well. SeaQuest aims to complement the flagship NuSea measurement by probing higher seaquark momenta at a lower center-of-mass energy and higher intensity. A summary of the light-quark flavor asymmetry measurement status will be reported as well as the status of various parallel analyses, one of which could have implications for the Boer-Mulders initial state TMD.
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Center for Functional Nanomaterials Seminar
"Using Modeling and Machine Learning to Accelerate High-Throughput Experimental Materials Discovery"
Presented by Jason R. Hattrick-Simpers, National Institute of Standards and Technology
Monday, November 13, 2017, 11 am
CFN, Bldg. 735, Conference Room A, 1st FloorHosted by: Matthew Sfeir
Over the past 10 years there has been a resurgent interest in the development of novel metallic alloys, both as multiple principle component solid solution alloys, so-called high entropy alloys (HEA) as well as amorphous metallic glasses. Although a number of empirical rules have been proposed for the prediction of potential alloy compositions, calculating their stability and quantifying their properties of interest at operating temperatures from first principles represents a significant challenge. In fact, even high-throughput experimental studies struggle to effectively explore such large composition-processing-property parameter spaces efficiently. Here, I will discuss an approach that seeks to address the rational experimental exploration of such alloys by combining theory, experiment and data science. Our approach is to use insights from the literature, theory, and/or data mining to identify the regions of parameter space most likely to yield interesting materials. We then employ computationally guided high-throughput synthesis techniques to strategically probe composition and processing space. In situ synchrotron diffraction studies yield tens of thousands of data sets describing the evolution of the alloy phase and corrosion products. The data are evaluated using automated knowledge extraction techniques, enabling us to assess our experiments, update the models used to generate the initial lead materials, and plan the next material system to study. In this talk, I will emphasize our recent work using these techniques to investigate phase stability in metallic glasses.
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Condensed-Matter Physics & Materials Science Seminar
"Quasiparticle spectra from stochastic many-body methods"
Presented by Vojtech Vlcek, University of California, Los Angeles
Thursday, November 9, 2017, 1:30 pm
ISB Bldg. 734 Conf. Rm. 201 (upstairs)Hosted by: Gabi Kotliar
I will present new developments and applications of stochastic approaches to electronic structure and many-body perturbation theory, which overcome the steep scaling of conventional deterministic schemes. The general principles of linear-scaling stochastic methods for TDDFT, GW and BSE will be discussed and exemplified on realistic nanoscale systems with more than 5000 valence electrons. The stochastic approaches enable mapping the evolution of optical absorption, spectral functions and quasiparticle energies and lifetimes, as well as the emergence of collective excitations, over the full range from molecules to large bulk-like 3D nanoclusters and 2D layers.
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HET Seminar
"Tomorrow's Colloquium: Joanna Kiryluk: IceCube: Understanding the High Energy Universe with Cosmic Neutrinos"
Presented by Linda Carpenter, Ohio State University
Wednesday, November 8, 2017, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Sally Dawson
Though the Higgs has a non trivial branching fraction -8 percent, to light jets, this is a very hard channel to directly capture with the LHC. We study the Higgs boson (h ) decay to two light jets at the 14 TeV High-Luminosity-LHC (HL-LHC), where a light jet (j ) represents any nonflavor-tagged jet from the observational point of view. The decay mode Higgs to gluons is chosen as the benchmark since it is the dominant channel in the Standard Model, but the bound obtained is also applicable to the light quarks. We estimate the achievable bounds on the decay branching fractions through the associated production V h (V =W±,Z ). Events of the Higgs boson decaying into heavy (tagged) or light (untagged) jets are correlatively analyzed. We find that with 3000 fb-1 data at the HL-LHC corresponds to a reachable upper bound of a few times the SM prediction. Which can ten be turned into a bound on the Higgs couplings to gluons and light quark flavors. A consistency fit also leads to an upper bound on the Higgs to charm coupling. The estimated bound may be further strengthened by adopting multiple variable analyses or adding other production channels.
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Physics Colloquium
"Building an entanglement sharing quantum network"
Presented by Professor Eden Figueroa, Stony Brook University
Tuesday, November 7, 2017, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Andrei Nomerotski
In the first part of our talk we will show how to produce photonic quantum entanglement and how to store it and distribute it by optically manipulating the properties of room temperature atomic clouds. We will discuss our recent experiments in which several quantum devices are already interconnected forming an elementary quantum cryptographic network. We will also discuss our progress regarding the construction of an entanglement sharing link between Stony Brook and BNL. In the second part we will show our progress regarding the construction of an analog quantum computer capable of simulating relativistic dynamics using atoms and quantized light. We will show how our device is already capable of simulating Dirac and Jackiw-Rebbi Hamiltonians as well as the road map towards simulating Quantum Field Theory Hamiltonians.
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Condensed-Matter Physics & Materials Science Seminar
"Proximity effects in cuprate/manganite multilayers"
Presented by Christian Bernhard, University of Fribourg, Switzerland
Monday, November 6, 2017, 1:30 pm
ISB Bldg. 734 Seminar Room 201 (upstairs)Hosted by: Chris Homes
Recently we observed an intriguing, magnetic-filed-induced insulator-to-metal transition in YBa2Cu3O7/Pr1-xCaxMnO3 (YBCO/PCMO) multilayers [1]. In the low field regime, the response of these multilayers is highly resistive and resembles the one of granular superconductors or frustrated Josephson-networks. Notably, a coherent superconducting response can be restored with a large magnetic field. The latter also suppresses the charge/orbital order of the PCMO layers towards a ferromagnetic state. This coincidence suggests an intimate relationship between the insulator-to-superconductor transition in the YBCO layer and the suppression of the charge/orbital order in the PCMO. I will discuss the evidence, based on resonant x-ray scattering experiments, that the latter induces (or strongly enhances) a static Cu-CDW order in YBCO that is intertwined with superconductivity. [1] B.P.P. Mallett et al., Phys. Rev. B 94, 180503(R) (2016).
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Updated HET Lunch Discussions
""Dark Parity Violation After Qweak and Future Neutrino Physics Discussion" (Neutrino Discovery Initiative)"
Presented by William J. Marciano, BNL
Friday, November 3, 2017, 12:15 pm
Building 510, Room 2-160Hosted by: Christoph Lehner
To participate via BlueJean connection, please click on the following link: https://bluejeans.com/753838707/7269 Meeting ID: 753 838 707 Participate Passcode: 7269
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Condensed-Matter Physics & Materials Science Seminar
"Wandering amongst the Feynamn diagrams"
Presented by Nikolay Prokofiev, University of Massachusetts-Amherst
Friday, November 3, 2017, 11 am
ISB Bldg. 734 Conf. Rm. 201 (upstairs)Hosted by: Igor Zaliznyak
Feynman diagrams are the most celebrated and powerful tool of theoretical physics usually associated with the analytic approach. I will argue that diagrammatic expansions are also an ideal numerical tool with enormous and yet to be explored potential for solving interacting many-body systems by direct simulation of Feynman diagrams (bare or skeleton) for the proper self-energies and polarization operators up to high order. Though the original series based on are propagators are sign-alternating and often divergent one can determine the answer behind them by using proper series re-summation techniques and working with skeleton diagrams, i.e. by making the entire scheme self-consistent. The bottom line is that the diagrammatic Monte Carlo approach generically solves the computational complexity for interacting fermionic systems. In terms of physical applications, I will disucss results for the Hubbard model, resonant fermi gas at unitarity, and stability of Dirac liquid against strong Coulomb interaction in graphene.
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Particle Physics Seminar
"UCNtau: A magneto-gravitational trap measurement of the free neutron lifetime"
Presented by Robert Pattie, Los Alamos National Laboratory
Thursday, November 2, 2017, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Xin Qian
The neutron is the simplest nuclear system that can be used to probe the structure of the weak interaction and search for physics Beyond the Standard Model. Measurements of neutron ?-decay observables are sensitive to scalar and tensor interactions in the weak force which are not present in the Standard Model. The lifetime of the neutron ?n is an important parameter for Big-Bang Nucleo-synthesis models, solar fusion models, and absolute neutrino scattering cross-sections, and can be used to test the unitarity of the Cabibbo-Kobayashi-Maskawa quark mixing matrix. Presently, the two typical methods used to measure the neutron lifetime, cold neutron beam measurements and stored ultracold neutron (UCN) measurements, disagree by roughly 4?. This discrepancy motivates the need for new measurements with complementary systematic uncertainties to previous efforts. The UCN? experiment uses an asymmetric magneto-gravitational UCN trap with in situ counting of surviving neutrons to measure the neutron lifetime. Previous bottle experiments confined UCN in a material storage vessel creating a significant correction due to losses resulting from the material UCN interactions. The magnetic and gravitational confinement of the UCN minimizes losses due to material interactions. Additionally, UCN? uses a detection system that is lowered into the storage volume which avoids emptying the surviving UCN into an external detector. This minimizes any possible transport related systematics. This in situ detector also enables counting at various heights in the vessel, which provides information on the trapped UCN energy spectrum, quasi-bound orbits, and possible phase space evolution. I will present the physics motivation for precision neutron physics, a description of the UCN? experiment, the results of data collected during the 2016-2017 accelerator cycle which resulted in a value of τn=877.7±(0.7) stat (+0.3/−0.1) sys in agreement with previous material bottle
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Particle Physics Seminar
"Search for dark matter at the CMS experiment"
Presented by Adish Vartak, University of California San Diego
Friday, October 27, 2017, 10 am
Small Seminar Room, Bldg. 510Hosted by: Alessandro Tricoli
There is an extensive, on-going dark matter search program at the LHC that explores several different types of possible interactions between WIMP-like dark matter and standard model particles. The dark matter searches at the LHC are complementary, and in case of certain models, significantly more sensitive than the direct and indirect dark matter searches. In this talk I will discuss several key dark matter searches being pursued by the CMS collaboration. These cover a wide variety of final states in which dark matter particles are produced in association with one or more energetic, visible objects in the detector resulting in 'MET+X' signatures. Furthermore, I will also discuss the constraints set on dark matter interactions by certain resonance searches.
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Particle Physics Seminar
"Observation of Coherent Elastic Neutrino-Nucleus Scattering by COHERENT"
Presented by Kate Scholberg, Duke University
Thursday, October 26, 2017, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Xin Qian
Coherent elastic neutrino-nucleus scattering (CEvNS) is a process in which a neutrino scatters off an entire nucleus at low momentum transfer, and for which the observable signature is a low-energy nuclear recoil. It represents a background for direct dark matter detection experiments, as well as a possible signal for astrophysical neutrinos. Furthermore, because the process is cleanly predicted in the Standard Model, a measurement is sensitive to beyond-the-Standard-Model physics, such as non-standard interactions of neutrinos. The process was first predicted in 1973. It was measured for the first time by the COHERENT collaboration using the high-quality source of pion-decay-at-rest neutrinos from the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory and a CsI[Na] scintillator detector. This talk will describe COHERENT's recent 6.7-sigma measurement of CEvNS, the status and plans of COHERENT's suite of detectors at the SNS, and future physics reach.
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RIKEN Lunch Seminar
"Approach to equilibrium of quarkonium in quark-gluon plasma"
Presented by Xiaojun Yao, BNL
Thursday, October 26, 2017, 12:30 pm
Building 510, Room 2-160Hosted by: Hiromichi Nishimura
Quarkonium can be used as a probe of quark-gluon plasma (QGP) in heavy ion collisions. The production process is complicated by several factors: plasma screening effect, in-medium dissociation and recombination, cold nuclear matter effect and feed-down contributions. In this talk, I will present a set of Boltzmann transport equations that govern the in-medium evolution of the heavy quark and quarkonium system. The dissociation and recombination rates are calculated from potential non-relativistic QCD at leading order. I will explain how the system reaches equilibrium in a QGP box and show how the system evolves under a boost invariant longitudinal expansion. I will argue that the angular distribution of quarkonium probes the stages at which recombination occurs. The presented framework will be extended in future work to include other factors influencing quarkonium production.
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Condensed-Matter Physics & Materials Science Seminar
"Theory and Computation Guided Discovery of New Thermoelectric Materials"
Presented by Vladan Stevanovic, Colorado School of Mines & National Renewable Energy Laboratory
Wednesday, October 25, 2017, 1:30 pm
ISB Bldg. 734, Conf. Rm. 201 (upstairs)Hosted by: Cedomir Petrovic
Progress in the widespread adoption of all solid heat-to-electricity technologies has largely been hindered by the absence of suitable thermoelectric materials. In pursuit for new thermoelectrics recent advances in large-scale deployment of first principles calculations could be useful in identifying new promising material systems. However, the need to predict electron and phonon transport properties with sufficient accuracy renders direct assessment of the thermoelectric figure of merit (zT) for large numbers of systems unfeasible. This is true even in the case of relatively simple semiconductor materials, which could be described by the computationally inexpensive single particle theories such as density functional theory (DFT). While the state-of-the-art DFT based approaches to charge carrier and heat transport of semiconductors can deliver desired accuracy, they are currently limited to relatively simple chemistries and/or case-by-case studies. In this talk I will discuss integrated theory-computation-experiment efforts in developing a robust set of material descriptors that: (1) are rooted in the Boltzmann transport theory, but do not rely on classic and largely inapplicable constant relaxation time or constant mean free path approximations, (2) are computationally tractable allowing material searches across large chemical spaces, and (3) are sufficiently accurate to provide reliable predictions. Our approach is demonstrated to correctly identify known thermoelectric materials1 and reliably suggest new and promising candidate semiconductors.2 At the end, I will review successes and failures in our quest for new thermoelectrics, and discuss dopability of semiconductors as the critical outstanding challenge in achieving high zT materials. 1. Yan, P. Gorai, B. Ortiz, S. Miller, S. A. Barnett, T. Mason, V. Stevanovic, and E. S. Toberer, "Material descriptors for thermoelectric performance", Energy Environ. Sci. 2. P. Gorai, V. Stevanovic, and E. Tobe
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Physics Colloquium
"The Path Forward in Gravitational-wave astronomy"
Presented by Zsuzsa Marka, Columbia University
Tuesday, October 24, 2017, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Peter Petreczky
On August 17, 2017 the merger of two neutron stars was detected in the form of gravitational-waves by LIGO/Virgo. As a result of over a decade long preparation for multimessenger observations the event was also seen electromagnetically across the full spectrum. The history and future of the multimessenger effort using gravitational-waves will be discussed from an instrumentalist viewpoint.
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Nuclear Physics Seminar
"To CME or not to CME? Implications of recent charge separation measurements in p(d)+Au, Au(Cu)+Au and U+U collisions for the chiral magnetic effect in heavy ion collisions"
Presented by Roy Lacey, Stony Brook University
Tuesday, October 24, 2017, 11 am
Small Seminar Room, Bldg. 510Hosted by: Bjoern Schenke
The observation of charge separation induced by the Chiral Magnetic Effect (CME), could provide crucial insights on anomalous transport and the interplay of chiral symmetry restoration, axial anomaly, and gluonic topology in the Quark Gluon Plasma (QGP) produced in heavy ion collisions. I will discuss recent differential charge separation measurements,for p(d)+Au, Au(Cu)+Au and U+U, with a correlator specifically designed to give discernible responses to CME-driven charge separation and non-CME backgrounds. Measurements which span the beam energy range Root_s = 19.5 - 200 GeV will be presented. The d(p)+Au results are observed to be consistent with the reduced magnetic field strength and the essentially random B-field orientations expected in these collisions. In contrast, the Au(Cu)+Au and U+U measurements validate the presence of CME-driven charge separation quantified by the Fourier dipole coefficient a1. Ongoing attempts for CME-signal quantification, as well as implications for the upcoming RHIC isobar run, will be discussed as well.
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Condensed-Matter Physics & Materials Science Seminar
"Pressure-driven collapse of Jeff=1/2 electronic state in a honeycomb iridate"
Presented by Young-June Kim, University of Toronto, Canada
Friday, October 20, 2017, 3 pm
ISB Bldg. 734 Conf. Rm. 201 (upstairs)Hosted by: Igor Zaliznyak
Orbital and spin degrees of freedom in heavy transition metal compounds can be locked into each other due to strong spin-orbit coupling. The magnetism in this case is described by an effective total angular momentum jeff=1/2 rather than usual spin angular momentum. Furthermore, these jeff=1/2 moments residing on a honeycomb lattice can be coupled through bond-dependent Kitaev interactions. Magnetic properties of some honeycomb lattice iridates, such as Na2IrO3 and Li2IrO3 have been extensively investigated to examine whether Kitaev quantum spin liquid is realized in these compounds. However, the applicability of the jeff=1/2 local moment model in real materials have not been critically scrutinized experimentally. A combination of x-ray absorption spectroscopy, x-ray diffraction, and resonant inelastic x-ray scattering experiments on a honeycomb lattice Li2IrO3 reveals that the jeff=1/2 picture breaks down under high pressure, and electrons take on more itinerant character under this condition.
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Nuclear Theory/RIKEN Seminar
"Quantization of three-body scattering amplitude in isobar formulation"
Presented by Maxim Mai, George Washington University
Friday, October 20, 2017, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Chun Shen
In the so-called isobar parametrization the three-particle states are populated via an interacting two-particle system (resonant or non-resonant), and a spectator. Using this parametrization, we derive the isobar-spectator interaction such that the three-body Unitarity is ensured exactly. In the first part of my talk I will show the major steps of this derivation. (arXiv:1706.06118) The second part of the talk will be dedicated to the finite-volume implementation of the framework (arXiv:1709.08222). Imaginary parts in the infinite volume, dictated by Unitarity, determine the dominant power-law finite volume effects to ensure the correct 3-body quantization condition. Furthermore, various building blocks of the 3->3 amplitude in the finite volume can become singular. However, when all contributions are summed-up, only genuine 3-body singularities remain. I will demonstrate the corresponding cancellation mechanisms explicitly for the simplified case of only one S-wave isobar.
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Particle Physics Seminar
"Study of the Higgs properties in the H->ZZ*->4l channel with the ATLAS detector"
Presented by Gaetano Barone, Brandeis University
Thursday, October 19, 2017, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Alessandro Tricoli
Recent measurements of the Higgs boson properties in the four lepton channel for 36.1 fb-1 of proton—proton collisions at 13 TeV using the ATLAS detector will be presented. The measurements include the Higgs boson mass as well as inclusive, fiducial and differential cross sections and, constraints on Higgs boson production couplings. The results are interpreted within the Standard Model and various extensions.
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RIKEN Lunch Seminar
"Lattice QCD and Neutrino Physics"
Presented by Aaron Meyer, HET Group
Thursday, October 19, 2017, 12:30 pm
Building 510, Room 2-160Hosted by: Enrico Rinaldi
The nucleon axial form factor is a dominant contribution to systematic uncertainties in neutrino oscillation studies. The most commonly used model parametrization of the axial form factor has uncontrolled and underestimated systematic errors. First-principles computations from lattice QCD have the potential to control theory errors by disentangling the effects of nuclear corrections from the nucleon amplitudes. In this talk, I discuss fits to the axial form factor with deuterium bubble chamber data using the model-independent $z$ expansion parameterization. I then present preliminary results for a blinded lattice QCD calculation of the nucleon axial charge $g_A$ with physical light quark masses. This calculation is being done with the Highly Improved Staggered Quark (HISQ) action and 2+1+1 flavors of sea quarks.
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Environmental & Climate Sciences Department Seminar
"Desert Dust, Wildfire Smoke, Volcanic Ash, Urban and Industrial Pollution – Grasping the Role Particles Play in Global Climate and Regional Air Quality"
Presented by Ralph Kahn, NASA Goddard Space Flight Center
Thursday, October 19, 2017, 11 am
Conference Room Bldg 815EHosted by: Steve Schwartz
Airborne particles are ubiquitous components of our atmosphere, originating from a variety of natural and anthropogenic sources, exhibiting a wide range of physical properties, and contributing in multiple ways to regional air quality as well as regional-to-global-scale climate. Most remain in the atmosphere for a week or less, but can traverse oceans or continents in that time, carrying nutrients or disease vectors in some cases. Bright aerosols reflect sunlight, and can cool the surface; light-absorbing particles can heat the atmosphere, suppressing cloud formation or mediating larger-scale circulations. In most cases, particles are required to collect water vapor as the initial step in cloud formation, so their presence (or absence) and their hygroscopic or hydrophilic properties can affect cloud occurrence, structure, and ability to precipitate. Grasping the scope and nature of aerosol environmental impacts requires understanding microphysical-to-global scale processes, operating on timescales from minutes to days or longer. Satellites are the primary source of observations on kilometer-to-global scales. Spacecraft observations are complemented by suborbital platforms: aircraft in situ measurements and surface-based instrument networks that operate on smaller spatial scales, some on shorter timescales. Numerical models play a third key role in this work — providing a synthesis of current physical understanding with the aggregate of measurements, and allowing for some predictive capability. This presentation will focus on what we can say about aerosol amount and type from space. Constraining particle "type" is at present the leading challenge for satellite aerosol remote sensing. We will review recent advances and future prospects, including the strengths and limitations of available approaches, and current work toward better integrating measurements with models to create a clearer picture of aerosol environmental impacts, globally.
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Particle Physics Seminar
"The R&D and Mass Production of 20"MCP-PMT for Neutrino Detection"
Presented by Dr. Sen Qian, IHEP China
Monday, October 16, 2017, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Xin Qian
Researchers at IHEP, Beijing have conceived a new concept of MCP-PMT several years ago. The small MCP (Microchannel Plate) units replace the bulky Dynode chain in the tranditional large PMTs for better photoelectron detection. After three years R&D, a number of 8 inch prototypes were produced and their performance was carefully tested at IHEP in 2013 by using the MCP-PMT evaluation system built at IHEP. The 20 inch prototypes were followed in 2014, and its' performance were improving a lot in 2015. Compensating the PMT performances with fiducially volume convert all specifications to cost, radioactivity, dark noise, TTS, the JUNO ordered 15000 pic 20-inch MCP-PMT from the NNVT in Dec.2015. In 2016, the MCP-PMT collaboration group finished to build the mass production line in Nanjing at the end of 2016, and finished the batch test system in the same place within 100 days at the beginning of 2017. From 2017 to 2019, all the 20-inch MCP-PMT will be produced and tested one by one in NNVT for JUNO. This presentation will talk about the R&D process and mass production, batch test result of the first 2K pieces of MCP-PMT prototypes for JUNO.
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Condensed-Matter Physics & Materials Science Seminar
"Domain walls and phase boundaries - new nanoscale functional elements in complex oxides"
Presented by Jan Seidel, UNSW Sydney
Monday, October 16, 2017, 1:30 pm
Bldg. 480, Conference RoomHosted by: Myung-Geun Han
Topological structures in functional materials, such as domain walls and skyrmions, see increased attention due to their properties that can be completely different from that of the parent bulk material [1]. I will discuss recent results on multiferroic phase boundaries, domain walls in BiFeO3 [2, 3, 4, 5, 6] using SPM, TEM and ab-initio theory, and discuss future prospects [7]. References [1] J. Seidel (ed.), Topological structures in ferroic materials: domain walls, skyrmions and vortices, ISBN: 978-3-319-25299-5, Springer, Berlin (2016) [2] P. Sharma, et al., Scientific Reports 6, 32347 (2016) [3] P. Sharma, et al., Advanced Electronic Materials 2, 1600283 (2016) [3] J. Seidel, et al., Advanced Materials 26, 4376 (2014) [4] Y. Heo, et al., Advanced Materials 26, 7568 (2014) [5] Y. Heo et al., ACS Nano, DOI: 10.1021/acsnano.6b07869 (2017) [6] P. Sharma, et al., Advanced Materials Interfaces 3, 1600033 (2016) [7] J. Seidel, Nature Nanotechnology 10, 190 (2015)
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Nuclear Theory/RIKEN Seminar
"What can we learn from flow observables in heavy-ion collisions?"
Presented by Jacquelyn Noronha-Hostler, Rutgers University
Thursday, October 12, 2017, 12:30 pm
Building 510, Room 2-160Hosted by: Chun Shen
The Quark Gluon Plasma (QGP), nature's first and most perfect liquid, has been successfully reproduced in heavy-ion collisions at RHIC and the LHC. The dynamics of the QGP can be well described by relativistic viscous hydrodynamics, allowing for precise comparisons to experimental data in order to extract the properties of the QGP. While a small shear viscosity is well-established, questions still remain regarding the precise initial state, the temperature dependence of viscosity, the smallest system that displays QGP-like properties, and the equation of state at large densities. In this talk, the various flow harmonic observables are analyzed to help answer these remaining questions.
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Nuclear Physics Seminar
"The nature of flow fluctuations, from pp to A+A, and back again"
Presented by Mingliang Zhou, Stony Brook University
Tuesday, October 3, 2017, 11 am
Small Seminar Room, Bldg. 510Hosted by: Jiangyong Jia
In recent years, there have been rapid progresses in our understanding of the event-by-event flow fluctuation, which provides direct insight into the fluctuations in the initial geometry. I will start my talk by briefly discussing the flow (collectivity) and its fluctuation in small systems pp and p+Pb, using the newly-proposed subevent cumulant method, which is able to suppress the non-flow background effectively. I will show there is significant fluctuation of elliptic flow $v_2$ in pp and non-Gaussian fluctuation of triangular flow $v_3$ in p+Pb. Moving from small to large systems, STAR collaboration recently has shown different behaviors of cumulant $c_2\{4\}$ between Au+Au and U+U in ultra-central collisions, which is believed to support the different geometry fluctuations. By presenting the newest ATLAS flow measurements in ultra-central collisions, together with detailed MC Glauber studies, I will explain why sign change of $c_2\{4\}$ is observed and its implications. In the end, I will go back to small systems and discuss the potential impact of centrality resolution on pp flow measurements.
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Particle Physics Seminar
"Latest Results from the T2K Experiment"
Presented by Kendall Mahn, Michigan State University
Friday, September 29, 2017, 3:30 pm
Small Seminar Room, Bldg. 510Hosted by: Xin Qian
One of the most promising investigations of beyond-the-Standard-Model physics has been the study of neutrino oscillation, that is, the conversion of neutrinos from one flavor to another as they propagate. While neutrino oscillation is studied in a wide variety of experiments, accelerator based experiments, such as T2K, use a muon neutrino or antineutrino beam as a source to look for electron (anti)neutrino appearance, muon neutrino disappearance. The source also is used to make measurements of neutrino interactions and search for exotic physics. This talk will describe a recent analysis of both neutrino and antineutrino beam data from T2K. Comparisons between neutrino and antineutrino event rates provide a tantalizing window on possible CP violation in the neutrino sector. The talk will also highlight the increasingly important role of systematic uncertainty assessment for T2K and other future measurements of CP violation with accelerator beams.
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Nuclear Theory/RIKEN Seminar
"QCD on a small circle"
Presented by Aleksey Cherman, University of Washington
Friday, September 29, 2017, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Heikki Mantysaari
Recent developments have shown that QCD-like theories can be engineered to remain in a confined phase when compactified on an arbitrarily small circle, where their features may be studied quantitatively in a controlled fashion. I'll explain how a non-perturbative mass gap and chiral symmetry breaking, which are both historically viewed as prototypical strong coupling effects, appear from systematic weak-coupling calculations. Then I'll describe the rich spectrum of hadronic states, including glueball, meson, and baryon resonances in the calculable small-circle context.
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Particle Physics Seminar
"Beauty and charm decays and physics beyond the Standard Model: an experimentalist perspective"
Presented by Marina Artuso, Syracuse University
Thursday, September 28, 2017, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Alessandro Tricoli
The Standard Model provides a comprehensive explanation for a vast array of data collected at different experiments. Nonetheless fundamental questions remain unanswered and the search for a more complete theory is still a coveted goal of particle physics. Recently, tensions with standard model predictions have been uncovered in several experimental observables in b-hadron decays at LHCb. I will discuss the data, possible implications, and the connection with other experimental programs such as study of kaon rare decays and neutrino mixing and CP violation
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Condensed-Matter Physics & Materials Science Seminar
"Suppression of weak ferromagnetism in ultrathin iridates by interfacial engineering of octahedral rotations"
Presented by Yuefeng Nie, Nanjing University, China
Thursday, September 28, 2017, 1:30 pm
ISB Bldg. 734 Conf. Rm. 201 (upstairs)Hosted by: Weiguo Yin
Layered iridates, Srn+1IrnO3n+1, have drawn great attention since they share remarkable similarities with high-Tc cuprates, including layered crystalline structure, (pseudo) spin ½ states, antiferromagnetic (AFM) Mott insulating ground state, Fermi arcs, and V shape energy gap, etc. Nonetheless, direct evidences of superconductivity such as zero resistivity and Meissner effect are still lacking up to date. The strong spin-orbit coupling and IrO6 octahedral rotations in 5d iridates result in a canted AFM ground state with weak ferromagnetic moments in each IrO2 plane. Here, we propose to suppress the weak ferromagnetism by suppressing the octahedral rotations in iridates, which may facilitate the Cooper pairing. Using a combination of reactive molecular beam epitaxy (MBE), in situ angleresolved photoemission spectroscopy (ARPES) and first principle calculations, we investigate the evolution of octahedral rotations, electronic structure and magnetic ordering in ultra-thin SrIrO3 films grown on (001) SrTiO3 substrate. Our experimental results and theoretical calculations show that octahedral rotations and weak ferromagnetic moments are fully suppressed in 1 and 2 unit cell thick SrIrO3 films through interfacial clamping effects. If time allows, I will also present our recent work on the new understanding of RHEED oscillations in the growth of oxides and the chemically specific termination control of oxide interfaces via layerby- layer mean inner potential engineering.
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RIKEN Lunch Seminar
"Color Memory, Large Gauge Transformations, and Soft Theorems in Yang-Mills Theory"
Presented by Monica Pate, Harvard University
Thursday, September 28, 2017, 12:30 pm
Building 510, Room 2-160Hosted by: Hiromichi Nishimura
An infinite dimensional symmetry group which governs the infrared sectors of gauge and gravity theories has been recently discovered. This symmetry can be established both from an asymptotic symmetry analysis as well as from the corresponding Ward identities which are quantum field theoretic soft theorems. Moreover, the spontaneous breaking of these symmetries induces vacuum transitions which are detectable by charged particles through the so-called memory effect. In this seminar, I will explain the precise equivalence between asymptotic symmetries, soft theorems and memory effects in the context of tree level Yang-Mills. In particular, in this context the soft gluon theorem is Ward identity of a large gauge symmetry, whose action on the vacuum can be measured from the relative color charge of colored detectors.
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Condensed-Matter Physics & Materials Science Seminar
"Ultrafast TEM and Time-of-Flight EELS using microwave cavities"
Presented by Jom Luiten, Eindhoven University of Technology, Netherlands
Friday, September 22, 2017, 11 am
Bldg. 480, Conference RoomHosted by: Yimei Zhu
Ultrafast Transmission Electron Microscopy (U-TEM) has become a very important tool for the study of ultrafast phenomena at (sub-)nm length scales and (sub-)ps time scales. U-TEM is usually based on the creation of ultrashort electron pulses by femtosecond laser photoemission from a flat cathode, with the result that both the beam quality and the average current are significantly less than in state-of-the-art continuous-beam TEMs. At Eindhoven University we have developed U-TEM in which ultrashort electron pulses are produced by using a 3 GHz deflecting microwave cavity in TM110 mode to sweep a high-brightnes continuous beam across a slit [1]. We have demonstrated ultrafast beam chopping with conservation of the beam quality and the sub-eV energy spread of the FEG source of an adapted 200 keV Tecnai TEM, enabling atomic resolution with sub-ps temporal resolution at 3 GHz rep rate [2] In addition we have developed a new method for doing Time-of-Flight Electron Energy Loss Spectroscopy (ToF-EELS) based on the combined use of two TM110 deflecting cavities and two TM010 (de)compression cavities. The first 'chopping' TM110 cavity produces ultrashort electron pulses which are sent through a sample. Energy loss in the sample translates into reduction of the electron velocity and thus into a later arrival time at the detector, which is measured with a synchronized second TM110 'streak' cavity. In this way an energy resolution of 12 eV at 30 keV has been demonstrated [3]. By adding a TM010 (de)compression cavity after the sample, the longitudinal phase space can be manipulated in such a way that the energy resolution is improved to 2 eV (to be published). By adding a second TM110 cavity before the sample, full control over the longitudinal phase space can be achieved. Detailed charged particle tracking simulations show that an energy resolution of 20 meV combined with a temporal resolution of 2 ps can be achieved; or, alternatively, 2
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Particle Physics Seminar
"Evidence for the H to bb decay with the ATLAS detector"
Presented by Giacinto Piacquadio, Stony Brook University
Thursday, September 21, 2017, 4 pm
Small Seminar Room, Bldg. 510Hosted by: Alessandro Tricoli
Most Higgs bosons are expected to decay to a pair of b-quarks, with the Standard Model predicting a branching fraction of about 58%. Probing this decay is important to furthering our understanding of the Higgs sector, but its observation at hadron colliders is complicated by overwhelming Standard Model backgrounds. In this seminar, the search for the Higgs to bb decay, looking at the associated production of the Higgs boson with a W or Z boson, is presented, based on 36 fb-1 of 13 TeV LHC Run 2 data.
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Condensed-Matter Physics & Materials Science Seminar
"Two new applications of geometric critical phenomena for disordered electron systems"
Presented by Matthew Foster, Rice University
Thursday, September 21, 2017, 1:30 pm
ISB Bldg. 734 Conf. Rm. 201 (upstairs)Hosted by: Robert Konik
I will discuss two very recent results relating to the properties of electrons in two spatial dimensions (2D), subject to the effects of quenched disorder (impurities) and quantum interference [Anderson (de)localization]. In both cases, the key physics is tied to classical geometric critical phenomena in 2D. I will first present numerical evidence that strongly suggests the equivalence of disordered surface states of topological superconductors and geometric percolation. Percolation is known to play a role in quantum Hall systems with magnetic fields. Our unexpected result implies that percolation applies to topological superconductor surface states in the absence of time-reversal symmetry breaking. Moreover, the usual "even-odd" effect that occurs in such a system (as identified by Pruisken in the integer quantum Hall effect and by Haldane for spin chains) is found to be absent. Second, I will discuss a "toy model" for the ergodic to many-body localized phase transition in 2D, and relate it to an effective self-interacting walk. I will present analytical results of a controlled expansion which suggest that the transition can be viewed as a "dephasing catastrophe."
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Nuclear Theory/RIKEN Seminar
"TMD gluon distributions for dijet production and their behavior at small x"
Presented by Elena Petreska, NIKHEF
Friday, September 15, 2017, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Heikki Mantysaari
Starting from the Color Glass Condensate (CGC) cross section for dijet production in proton-nucleus collisions we derive a transverse-momentum-dependent (TMD) factorization formula for small transverse-momentum imbalance of the jets and for finite number of colors. For the eight TMD distributions appearing in the cross section we determine their operator definitions at small-x as CGC correlators of Wilson lines and we study their JIMWLK evolution. We find that at large transverse momentum the universality of TMDs gets restored. We also discuss an extension of the approach to generalized TMDs (GTMDs) that can give an insight into the angular correlations between impact parameter and dipole size in the CGC framework.
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Particle Physics Seminar
"SB/BNL Joint Cosmo seminar (at BNL): Mapping the Cosmos with the Dark Energy Survey"
Presented by Dr. Chihway Chang, ETH Zurich
Thursday, September 14, 2017, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Erin Sheldon
The first year data from the Dark Energy Survey (DES Y1) provides the most powerful optical survey dataset to date. In this talk I will first give an overall summary of the cosmology results from the DES Y1 dataset combining galaxy clustering and weak gravitational lensing. Next, I will describe our work in generating and testing the wide-field weak lensing mass maps from the galaxy shape measurements and some exciting applications for the maps. I will end with thoughts on how weak lensing could also inform us on various topics of galaxy formation, which is essential for completing the story behind the Universe we see today.
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RIKEN Lunch Seminar
"Thermal Fluctuations in Hydrodynamic Simulations of QGP"
Presented by Mayank Singh, McGill University
Thursday, September 14, 2017, 12:30 pm
Building 510, Room 2-160Hosted by: Hiromichi Nishimura
Multi-particle correlations measured in heavy-ion collision experiments carry info on fluctuations present in the entire evolutionary history of the system. Initial states include geometric and quantum fluctuations and are important contributors. The thermal fluctuations during the course of QGP evolution is another conceptually important source of these fluctuations and should be studied in detail. We begin by treating thermal fluctuations as a linearized perturbation on hydrodynamic background. We present a full calculation of hadronic and photonic observables including these fluctuations. Recently we have included fluctuations in our simulations in a non-perturbative manner. Progress based on this approach will be discussed.
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Physics Colloquium and Leona Woods Lecture
"Momentum-space structure of hadrons and nuclei at high energy"
Presented by Elena Petreska, NIKHEF
Tuesday, September 12, 2017, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Peter Petreczky
Transverse-momentum-dependent (TMD) distributions describe the configuration of quarks and gluons inside protons and nuclei in three-dimensional momentum space. Observables in scattering experiments can be calculated with the help of TMD factorization formulas, where the target and projectile are represented with non-perturbative TMD distributions, which are separated from the short-distance perturbative part of the collision. A complementary approach to study the momentum structure of protons and nuclei at high energy is the Color Glass Condensate which is an effective theory for the high-gluon-density region of ultra-relativistic particles. We introduce both theories and we discuss connections between them. We present phenomenological results derived from these connections.
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NSLS-II Seminar
"On the assessment of radiation damage and high temperature effects in novel nuclear materials using the BNL accelerators and synchrotrons"
Presented by Nick Simos, Sr Scientist Emeritus, BNL
Friday, September 8, 2017, 3 pm
Large Seminar Room, Bldg. 510Hosted by: Ron Pindak
In search for new and improved materials, composites and super-alloys capable of withstanding the anticipated extreme states associated fusion reactors; high temperature fast reactors and multi-MW particle accelerators, novel reactor steels, super-alloys and composites are continuously being explored to help meet both the challenge of the higher demand environments and the intended application. Higher fluxes and fluences of irradiating species (neutrons and/or protons), extreme temperatures and aggressively corrosive environments make up the new cocktail of operating conditions of the new array of material structures. One of the challenges in characterizing the effects that high radiation fluxes of neutrons and protons induce on these novel material structures in conjunction with high temperatures is the link between lattice induced damage and phase transformation and macroscopic physical properties which ultimately determine performance in the real environment. High energy X-rays at the BNL synchrotrons have offered a path in establishing this important connection between micro-scale effects and physical properties of novel material structures exposed to high radiation fluxes. Specifically, by integrating the unique capabilities of the BNL accelerator complex that includes, in addition to the NSLS and NSLS II, the proton accelerator and Tandem as well as those of CFN, the evolution and/or damage of materials ranging from classical structures such as graphite, beryllium and steels to novel super-alloys, such as those of Invar and "Gum" metal, and new composites have been characterized both at the two length scales. The pivotal role of high energy X-rays from NSLS to NSLS II in making the connection will be presented demonstrating the enormous potential of the NSLS II in answering fundamental questions in our path towards the next generation nuclear materials. Furthermore, first glimpses of the correlation of lattice effects or damage induced by differ
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NSLS-II Colloquium Series
"Experiments, Analyses, and Manipulations with Particle Beam"
Presented by Shyh-Huan Lee, Indiana University, IN
Thursday, September 7, 2017, 4 pm
Large Seminar Room, Bldg. 510Hosted by: John Hill
Progress on particle beam physics research have provided marked improvements in beam intensity, brightness, and stability advancing frontier research in applied and fundamental science. This talk will review some beam measurements and manipulation studies being undertaken to improve beam performance in storage rings. Hopefully, these studies will be relevant to the operation and improvement of National Accelerator User Facilities.
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Particle Physics Seminar
"Radiation damage study of a thin YAG:Ce scintillator using low-energy protons"
Presented by Dr. Vladmir Linhart, Czech Technical University in Prague
Thursday, September 7, 2017, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Xin Qian
Radiation hardness of a 50µm thin YAG:Ce scintillator in a form of dependence of a signal efficiency on 3.1MeV proton ?uence was measured and analyzed using X-ray beam. The signal efficiency is a ratio of signals given by a CCD chip after and before radiation damage. The CCD chip was placed outside the primary beam because of its protection from damage which could be caused by radiation. Using simplified assumptions, the 3.1MeV proton fluencies were recalculated to: • 150 MeV proton fluencies with intention to estimate radiation damage of this sample under conditions at proton therapy centers during medical treatment, • 150 MeV proton doses with intention to give a chance to compare radiation hardness of the studied sample with radiation hardness of other detectors used in medical physics, • 1 MeV neutron equivalent fluencies with intention to compare radiation hardness of the studied sample with properties of position sensitive silicon and diamond detectors used in nuclear and particle physics. The following results of our research were obtained. The signal efficiency of the studied sample varies slightly (±3%) up to 3.1MeV proton ?uence of c. (4 − 8) × 1014 cm−2. This limit is equivalent to 150MeV proton ?uence of (5 − 9) × 1016 cm−2, 150MeV proton dose of (350 − 600) kGy and 1MeV neutron ?uence of (1 − 2) × 1016 cm−2. Beyond the limit, the signal efficiency goes gradually down. Fifty percent decrease in the signal efficiency is reached around 3.1MeV ?uence of (1 − 2) × 1016 cm−2 which is equivalent to 150 MeV proton ?uence of around 2 × 1018 cm−2, 150MeV proton dose of around 15 MGy and 1 MeV neutron equivalent ?uence of (4 − 8) × 1017 cm−2. In contrast with position sensitive silicon and diamond radiation detectors, the studied sample has at least two order of magnitude greater radiation resistance. Therefore, YAG:Ce sci
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Simons Center for Geometry and Physics Public Lecture
"Mysteries of the Universe and Everyday Life"
Presented by Michelangelo Mangano; Young-Kee Kim; Joe Lykken, LHC/CERN; University of Chicago; Fermilab
Tuesday, September 5, 2017, 5:30 pm
Simons Center at Stony Brook University, Della PieIn the past few decades we have learned a great deal about the basic laws of Physics in the infinitely small – and the infinitely large – and how the two are intimately connected. New windows have expanded our understanding, and many unexpected questions have emerged. This is an exhilarating time in history. New tools, both theoretical and observational, may lead in the next decade to major advances in our understanding of the universe. As in the past, when major discoveries are made about the fundamental laws of Nature, not only is our view of the world enriched, but also our life is transformed. A good place to explore the discoveries from the past decades is in the description of symmetry, symmetry breaking and the Higgs boson in High Energy Physics: why, how and where to…. in a nutshell. These talks will present what we know and what we seek in the fundamental laws of Nature; how we go about answering basic questions in high energy experiments, how much we have learned, and how the technical developments needed to make discoveries have changed society. They will also delineate the boundaries of our knowledge and the known unknowns in fundamental high energy physics and cosmology.
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Particle Physics Seminar
"Wiener-SVD approach to data unfolding"
Presented by Dr. Hanyu Wei, BNL
Thursday, August 31, 2017, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Xin Qian
Data unfolding is a commonly used technique in the high energy physics experiments, to retrieve the distorted or transformed measurements by various detector effects. Inspired by the deconvolution technique in the digital signal processing, a new unfolding technique based on the Singular Value Decomposition (SVD) of the response matrix is developed. With the well-known Wiener filter concept, the modified SVD approach, Wiener-SVD, achieves the maximizing signal-to-noise ratio of the binned data in a transformed set of orthonormal bases where the uncertainties are bin-to-bin uncorrelated. In this talk, the mathematical principles and formulations of the newly developed Wiener-SVD unfolding will be presented. A few applications will be demonstrated. A comparison with the commonly used regularization method will also be shown. The advantages and disadvantaged of the Wiener-SVD approach will be discussed.
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Nuclear Theory/RIKEN Seminar
"QCD corrections to high-pT hadron production in ep scattering"
Presented by Werner Vogelsang, Tuebingen University
Friday, August 25, 2017, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Heikki Mantysaari
We discuss various cross sections and spin observables in high-pT hadron production in lepton proton collisions, with special focus on the role of perturbative QCD corrections. We present phenomenological studies relevant for present fixed-target experiments and for a future EIC.
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Particle Physics Seminar
"Precision tests with antimatter: A glimpse at the 1S – 2S transition in trapped antihydrogen"
Presented by Dr. William Bertsche, CERN
Thursday, August 24, 2017, 10 am
Small Seminar Room, Bldg. 510Hosted by: Xin Qian
Optical spectroscopy with antihydrogen atoms remains one of the most promising routes towards testing CPT invariance and physics beyond the Standard Model in an effort to address the observed Baryon asymmetry in the Universe today. The ALPHA collaboration has made significant progress towards the first measurements of optical transitions in trapped antihydrogen atoms, and has recently published the first observation of the 1S – 2S transition in a fully antimatter atom. This work finds the transition consistent with CPT invariance at a level of approximately 2 x 10-10 [1]. This talk will review the details of this pioneering experiment and discuss the prospects of future spectroscopy studies and other fundamental measurements with the ALPHA experiment. [1] M. Ahmadi, et al (ALPHA Collaboration), "Observation of the 1S–2S transition in trapped antihydrogen" Nature 541, 506–510 (2017).
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Condensed-Matter Physics & Materials Science Seminar
"Experiments on electron hydrodynamics with and without applied magnetic fields"
Presented by Andrew Mackenzie, Max-Planck-Institute, Germany
Wednesday, August 23, 2017, 1:30 pm
Bldg. 734, ISB Conf. Room 201 (upstairs)Hosted by: Cedomir Petrovic
Will discuss experiments aimed at probing signatures of viscous contributions to electrical transport in ultra pure metallic systems. The hydrodynamic regime was reached in semiconductor heterostructures in the 1990s, but has only recently come into reach in naturally occurring compounds. I will focus on our group's work on layered delafossite metals, but possibly also discuss results from other groups on different material families.
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Nuclear Theory/RIKEN Seminar
"Factorization and phenomenology for Transverse Momentum Dependent distributions"
Presented by Ignazio Scimemi, Universidad Complutense de Madrid
Friday, August 18, 2017, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Heikki Mantysaari
Factorization and phenomenology for Transverse Momentum Dependent distributions Abstract: The factorization of the hadronic part of the cross sections plays a central role in our comprehension of collider physics. I will review some aspects of the factorization, like the appearence of rapidity divergences and the related subtractions and log resummation (up to higher orders in QCD perturbative expansion) in transverse momentum dependent cross sections. As an application I will describe the inclusion of the TMD formalism in an analysis of vector boson production data.
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RIKEN Lunch Seminar
"Revisit the energy density and the gluon spectrum in the boost-invariant Glasma from a semi-analytic approach"
Presented by Ming Li
Thursday, August 17, 2017, 12:30 pm
Building 510, Room 2-160Hosted by: Hiromichi Nishimura
In high energy heavy-ion collisions, the soft degrees of freedom at the very initial stage after the collision can be effectively represented by strong classical gluonic fields within the Color Glass Condensate framework. Understanding the space-time evolution of the system is equivalent to solving the classical Yang-Mills equations for the gluonic fields. There have been many efforts in the past two decades in numerically solving these equations. In this talk, on the contrary, I will use a semi-analytic approach that assumes the solution has the form of a power series expansion in the proper time. I will discuss the energy-momentum tensor and the gluon spectrum obtained from this approach and make comparisons with the numerical results in the literature.
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Special Nuclear Theory Seminar
"Gluon orbital angular momentum at small-x"
Presented by Yoshitaka Hatta, YITP, Kyoto University
Wednesday, August 16, 2017, 10:30 am
Small Seminar Room, Bldg. 510Hosted by: Raju Venugopalan
After reviewing the general aspects of the partonic orbital angular momentum in QCD (rigorous definition, connection to the Wigner distribution, etc), I focus on the gluon OAM in the small-x regime and discuss its measurability and a possible relation to the polarized gluon distribution.
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Nuclear Theory/RIKEN Seminar
"Resummation of nonglobal logarithms in QCD"
Presented by Yoshitaka Hatta, Kyoto University
Friday, August 11, 2017, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Heikki Mantysaari
The large angle emission of soft gluons from QCD jets gives rise to the so-called nonglobal logarithms. In this talk I discuss the resummation of nonglobal logarithms at finite Nc with particular emphasis on its deep connection to the small-x logarithms in high energy scattering.
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Nuclear Theory/RIKEN Seminar
"General formulae for dipole Wilson line correlators with the Color Glass Condensate"
Presented by Kenji Fukushima, University of Tokyo
Friday, August 4, 2017, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Heikki Mantysaari
I talk about general formulae to compute Wilson line correlators with the Color Glass Condensate approximated by the McLerran-Venugopalan model. Specifically, as an application, I explain about a perturbative expansion of the dipole correlators in terms of 1/N_c to derive fully analytical expressions. I finally discuss the validity of the large-N_c expansion by calculating the higher-order harmonics of the flow observables in the dipole model.
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NSLS-II Friday Lunchtime Seminar Series
"From Particles to Patients: The Role of an Epoxide Hydrolase in P. Aeruginosa Virulence"
Presented by Kelli Hvorency, 2017 Julian D. Baumert. PhD. Thesis Award Winner, Dartmouth College
Friday, August 4, 2017, 12 pm
NSLS-II Bldg 743 (LOB 3), room 156Hosted by: Ben Ocko, Shirish Chodankar, Milinda Abeykoon, Juergen Thieme and Guimei Wang
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Particle Physics Seminar
"Latest Results from NOvA"
Presented by Louise Suter, Fermilab
Thursday, July 27, 2017, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Xin Qian
NOvA is a long-baseline neutrino experiment which utilizes two basically fully active, finely segmented, liquid scintillator detectors: a Near Detector located at Fermilab, and a Far Detector located in Ash River, MI, and situated roughly 14 mrad off Fermilab's NuMI beam. Using this narrow-band beam of mostly muon neutrinos we study the oscillation of these neutrinos over the 810 km baseline to measure the rate of electron neutrino appearing and of muon neutrinos and neutral current interactions disappearing between the two detectors. These are interpreted to give our latest measurements on the neutrino mass ordering, CP violation, the flavor content of the third neutrino mass eigenstate, and tests of the three-neutrino paradigm.
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Computational Science Initiative Event
"The AMReX Astrophysics Suite: Simulating the Stars at the Exascale"
Presented by Michael Zingale, Associate Professor, Dept. Of Physics and Astronomy, Stony Brook University
Thursday, July 27, 2017, 1:30 pm
Seminar Room, Bldg. 725Hosted by: Meifeng Lin
Astronomy is an observational science — we take data (primarily light) from the objects in the Universe and use this to infer how systems work. Astrophysical simulations allow us to perform virtual experiments on these systems, giving us the ability to see into stars in a way that light alone does not allow. Stellar systems can be modeled using the equations of hydrodynamics, together with nuclear reactions, self-gravity, complex equations of state, and at times, radiation (and magnetic fields). The resulting simulation codes are multiphysics and multiscale, and a variety of techniques have been developed to permit accurate and efficient simulations. We describe the adaptive mesh refinement (AMR) codes for astrophysics built upon the AMReX library: the AMReX Astrophysics Suite. We'll focus on the codes for stellar / nuclear astrophysics: Maestro and Castro. Maestro models subsonic stellar flows while Castro focuses on highly-compressible flows. They share the same microphysics (reaction networks, equations of state) and parallelization strategy. Through AMReX, we distribute boxes in our AMR hierarchy across nodes and we use OpenMP (via a logical tiling model in Castro) to spread the work on a box across cores in a node. Recently we've implemented a GPU strategy in AMReX that allows us to move the computational kernels onto GPUs to offload expensive calculations. We'll discuss the current performance of the hydrodynamics and reaction networks on GPUs and how our strategy will evolve in the future.
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Environmental & Climate Sciences Department Seminar
"Classifying Aerosol Particles with a Centrifugal Particle Mass Analyzer (CPMA)"
Presented by Kristen Okorn, Stevens Institute of Technology (SULI Student Summer 2017)
Thursday, July 27, 2017, 11 am
Conference Room Bldg 815EHosted by: Ernie Lewis
Although wood stoves are a carbon-neutral renewable energy source, they are the largest source of particulate matter (PM) emissions in New York State. A Differential Mobility Analyzer (DMA), which classifies particles by their mobility diameter, has traditionally been employed to characterize such particulate emissions. However, because the black carbon (BC) particles produced by combustion that contribute to PM are fractal, their mobility diameters are not equal to their mass-equivalent diameters. In contrast to the DMA, the Centrifugal Particle Mass Analyzer (CPMA) classifies aerosol particles by their mass, using two rotating cylinders and an electric potential; when the centrifugal and electrostatic forces on a particle are equal, it passes through. The CPMA can select particles with masses ranging from 2×10 4 to 1.05×103 fg (corresponding to diameters, for particles with density 1 g cm 3, ranging from 7 to 1300 nm). It can be operated in two different ways: the "Run" classification method can be used to select for a single particle mass, and the "Step Scan" method can be used to select particles over a set range of masses. A neutralizer must be used upstream of the CPMA to create a charge distribution on particles before they enter the instrument. A DMA can optionally be used to pre-select particles of a specific mobility diameter before entering the CPMA. Downstream of the instrument, a Condensation Particle Counter (CPC) must be used in order to determine the number concentration of particles that pass through the CPMA. The basic operating principles of the CPMA are discussed, and results are presented for its characterization of polystyrene latex (PSL) particles, ammonium sulfate particles, and emissions from a wood burning stove.
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Particle Physics Seminar
"W boson mass measurement with the ATLAS experiment"
Presented by Fabrice Balli, CEA Saclay
Thursday, July 20, 2017, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Alessandro Tricoli
The W boson mass is a fundamental parameter of the Standard Model (SM) and was measured by several experiments at high energy e+e- and ppbar colliders. This parameter's measurement has the biggest impact on indirect searches for new particles or interactions, by comparing the measurement of this parameter with the prediction from the SM. It was measured recently by the ATLAS experiment at LHC, using data recorded in 2011, with a centre of mass energy of 7 TeV. I will review the thorough work that was performed in the ATLAS collaboration for this measurement and will discuss some considerations for future measurements at the LHC.
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NSLS-II Friday Lunchtime Seminar Series
"Bio-cryo Electron Microscopy: The Opportunity and Plan" and "Characterizing Self-Assembled Nanoparticles Employed in Drug Delivery Systems"
Presented by Sean McSweeney and Kazuo Sakurai, NSLS-II, BNL and University of Kitakyushu
Friday, July 14, 2017, 12 pm
NSLS-II Bldg 743 (LOB 3), room 156Hosted by: Ben Ocko, Shirish Chodankar, Milinda Abeykoon, Juergen Thieme and Guimei Wang
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Physics Colloquium
"Anomalies in Reactor Neutrinos"
Presented by Chao Zhang, BNL
Tuesday, July 11, 2017, 3:30 pm
Large Seminar Room, Bldg. 510Nuclear reactors are one of the most intense, pure, controllable, cost-effective and well-understood sources of neutrinos. Reactor neutrinos have played a major role in the discovery of neutrinos and neutrino oscillations. However, recently there emerged a few anomalies from reactor neutrino experiments when compared with state-of-the-art model predictions. The anomalies include a 5.5% deficit of the integrated antineutrino flux, a discrepancy in the antineutrino prompt energy spectrum around 5 MeV, and a 7.8% deficit in the 235U antineutrino flux from the new fuel evolution analysis in the Daya Bay Experiment. In this talk, those anomalies and their implications will be discussed. A new reactor neutrino experiment, PROSPECT, is aiming to resolve the anomalies by precisely measuring the 235U antineutrino spectrum at a very short baseline. The status of the PROSPECT experiment will also be reported
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Nuclear Theory/RIKEN Seminar
"Holographic Pomeron: Scattering, saturation, entropy and black hole."
Presented by Ismail Zahed, Stony Brook
Friday, July 7, 2017, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Heikki Mantysaari
I will discuss the general nature of the holographic Pomeron as a quantum QCD string exchange in both flat and curved AdS space for both pp and ep collisions at either large energies or small x. This description leads naturally to the concept of wee-strings and their distribution both in rapidity and transverse space. The holographic Pomeron carries intrinsic temperature and entropy, with the latter being identical to the recently reported entanglement entropy. I will show that this non-perturbative description of the Pomeron cross over to the the perturbative one, with a phase boundary dominated by string balls, i.e. long and massive strings near their intrinsic Hagedorn temperature. These string balls lead to a distribution of large multiplicity pp events that is in agreement with the one reported for pp collisions at the LHC. I will show that at low-x, the quantum string is so entangled that very weak string self-interactions can cause it to turn to a black hole. I will suggest that low-x saturation occurs when the density of wee-strings reaches the Bekenstein bound, with a proton size that freezes with increasing rapidity.
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Nuclear Theory/RIKEN Seminar
"Probing Transverse Momentum Broadening in Heavy Ion Collisions"
Presented by Feng Yuan, LBL
Friday, June 30, 2017, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Heikki Mantysaari
In this talk, we will discuss the dijet azimuthal de-correlation in relativistic heavy ion collisions as an important probe of the transverse momentum broadening effects in heavy ion collisions. We take into account both the soft gluon radiation in vacuum associated with the Sudakov logarithms and the jet PT-broadening effects in the QCD medium. We find that the Sudakov effects are dominant at the LHC, while the medium effects can play an important role at RHIC energies. This explains why the LHC experiments have not yet observed sizable PT-broadening effects in the measurement of dijet azimuthal correlations in heavy ion collisions. Future investigations at RHIC will provide a unique opportunity to study the PT-broadening effects and help to pin down the underlying mechanism for jet energy loss in a hot and dense medium.
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Nuclear Physics Seminar
"Measurement of longitudinal flow correlations in 2.76 and 5.02 TeV Pb+Pb collisions with the ATLAS detector"
Presented by Peng Huo, Stony Brook University
Tuesday, June 27, 2017, 11 am
Small Seminar Room, Bldg. 510Hosted by: Jin Huang
Longitudinal dynamics has recently become a topic of great interest in the study of ultra-relativistic heavy ion collisions. Measurement of the longitudinal fluctuations of the flow harmonic coefficients $v_n$ and event-plane angles $\Psi_n$ can provide a more complete picture of space-time evolution of the hot, dense medium formed in heavy ion collisions. Longitudinal flow decorrelations can be modeled with two contributions: magnitude fluctuations and event plane twist. However, existing observables do not separate these two effects. In this analysis, a new 4-particle correlator is used to separate the event-plane twist from magnitude fluctuations in 2.76 and 5.02 Pb+Pb collisions. Results show both effects have a linear dependence on pseudorapidity separation for $v_{2-5}$, and show a small but measurable variation with collision energy. The correlation of $\Psi_n $ of different order are also expected to have longitudinal fluctuations due to the non-linear mixing effects between lower and higher order flow harmonics. First measurement of such non-linear mode-mixing effects as a function of pseudorapidity is also presented. These result will help to constrain initial conditions along longitudinal direction and also help understand the longitudinal evolution of the fireball.
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Condensed-Matter Physics & Materials Science Seminar
"Resonant inelastic X-ray scattering on "moderately correlated" quantum materials"
Presented by L. Andrew Wray, New York University
Thursday, June 22, 2017, 1 pm
ISB Bldg. 734 Conf. Rm. 201 (upstairs)Hosted by: Mark Dean
The resonant inelastic X-ray scattering (RIXS) technique is best known for significant breakthroughs in the investigation of strongly correlated materials such as cuprates. However, the rapid advancement of RIXS spectrographs has made it increasingly attractive to apply the technique to a broad range of quantum materials outside of this comfort zone. This talk will review lessons learned from our recent measurements on material systems that feature a balance of correlated and itinerant physics, including VO2, the hidden order compound URu2Si2, and Prussian blue analogue battery electrodes. RIXS spectra enable the first observation of important collective modes for these systems, and provide a look into how correlated electron symmetries are melted - or persist! - in relatively itinerant and covalent environments. The data also highlight the need for improved theoretical modeling and higher photon throughput to achieve deeper insights.
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Condensed-Matter Physics & Materials Science Seminar
"Tailoring Lattice and Charge at Complex Oxide Nanostructures and Interfaces"
Presented by Xia Hong, University of Nebraska-Lincoln
Tuesday, June 20, 2017, 11 am
Bldg. 480, Conference RoomHosted by: Yimei Zhu
Capitalizing on the energy competition of charge itineracy with the strong electron-electron and electron-phonon couplings, nanoscale manipulation of the charge and lattice degrees of freedom in strongly correlated oxides can often lead to new functionalities that are inaccessible in the bulk form. In this talk, I will present our studies of the emerging phenomena at epitaxial correlated oxide nanostructures and hetero-interfaces that result from the nanoscale lattice and charge control. By creating nanoscale periodic depth modulation, we have achieved a 50-fold enhancement of the magnetic crystalline anisotropy in ultrathin colossal magnetoresistive (La,Sr)MnO3, which is attributed to a non-equilibrium strain distribution established in the nanostructures [1]. I will also discuss the intricate interplay between epitaxial strain and electric field effect in determining the correlated transport of the charge transfer type Mott insulator (Sm,Nd)NiO3 [2,3], and how the interfacial charge transfer between two correlated oxides can be exploited to effectively engineer the performance of ferroelectric-gated Mott transistors [4]. [1] A. Rajapitamahuni et al., PRL 116, 187201 (2016). [2] L. Zhang et al., JPCM 27, 132201 (2015). [3] L. Zhang et al., APL 107, 152906 (2015). [4] X. Chen et al., Adv. Mater, in press (2017).
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Condensed-Matter Physics & Materials Science Seminar
"Laser-driven Pulsed Neutron Sources as a Potential Pool-side Characterization Tool for Nuclear Fuels"
Presented by Sven Vogel, Los Alamos National Laboratory
Monday, June 19, 2017, 1:30 pm
ISB Bldg. 734, Conf. Rm. 201 (upstairs)Hosted by: Emil Bozin
The unique advantages of neutrons for characterization of nuclear fuel materials [1] are applied at the pulsed spallation neutron source at LANSCE to accelerate the development and ultimately licensing of new nuclear fuel forms. Neutrons allow to characterize the crystallography of phases consisting of heavy elements (e.g. uranium) and light elements (e.g. oxygen, nitrogen, or silicon) [2]. The penetration ability in combination with comparably large (e.g. cm sized) beam spots provide microstructural characterization of typical fuel geometries for phase composition, strains, and textures from neutron diffraction. In parallel, we are developing energy-resolved neutron imaging and tomography with which we can complement diffraction characterization. This unique approach not only allows to visualize cracks, arrangement of fuel pellets in rodlets etc., but also characterization of isotope or element densities by means of neutron absorption resonance analysis [3]. Laser-driven pulsed neutron sources [4] have the potential to provide these capabilities "pool-side", e.g. at the Advanced Test Reactor at Idaho National Laboratory. Compared to proton accelerator driven spallation sources, requiring investments exceeding $1B, the investment cost for a laser-driven neutron source would be of the order of several $10M with the potential of similar flux to that of a smaller, earlier generation spallation neutron source. Compared to electron accelerator-driven neutron sources, the flux of a laser-driven source would be at least one order of magnitude higher. Compared to reactor neutron sources, the pulse structure of the laser-driven neutron source would enable unique characterization not possible with steady-state reactor neutrons. In this presentation, we provide an overview of our recent accomplishments in fuel characterization for accident-tolerant fuel consisting of uranium nitride/uranium silicide composite fuels as well as metallic fuels.
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Nuclear Theory/RIKEN Seminar
"Better fitting through (fictitious) chemistry"
Presented by Pasi Huovinen, Uniwersytet Wroclawski
Monday, June 19, 2017, 10 am
Small Seminar Room, Bldg. 510Hosted by: Heikki Mantysaari
One of the puzzles we have faced at the LHC is why the thermal models apparently cannot properly fit the yield of protons. I will explore how the fit improves if we assume that nucleon-antinucleon annihilations freeze-out way later than all other number changing processes or if strange particles freeze-out before non-strange particles, and how this affects the final particle distributions in hydrodynamical calculations.
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Nuclear Theory/RIKEN Seminar
"Exploring the phase structure and dynamics of QCD"
Presented by Jan Pawlowski, Heidelberg
Friday, June 16, 2017, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Heikki Mantysaari
The past years have seen tremendous progress in the description of Quantum Chromodynamics at vanishing and finite temperature and density with functional approaches, such as the functional renormalisation group or Dyson-Schwinger equations. Within these approaches QCD correlation functions of quarks, gluon and hadrons are computed non-perturbatively from first principles. In the talk I will discuss results for the phase structure of QCD at finite temperature and density, as well as for thermodynamical obserables such as the pressure and the trace anomaly. The approach is also applied to baryon number fluctuations. By now functional approaches also allow for a direct computation of transport coefficients in QCD. First results concern the temperature dependence of the shear viscosity over entropy ratio in Yang-Mills theory and QCD. The talk concludes with a discussion of the further prospects for our understanding of the phase structure and dynamics of QCD.
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Particle Physics Seminar
"First Results from XENON1T"
Presented by Dr. Fei Gao, Columbia University
Thursday, June 15, 2017, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Xin Qian
Understanding the properties of dark matter particle is a fundamental problem in particle physics and cosmology. The search of dark matter particle scattering off nuclei target using ultra-low background detector is one of the most promising technology to decipher the nature of dark matter. The XENON1T experiment, which is a dual phase detector with ~2.0 tons of xenon running at the Gran Sasso Laboratory in Italy, is designed to lead the field of dark matter direct detection. Since November 2016, the XENON1T detector is continuously taking data, with a background rate of more than one order of magnitude lower than any current generation dark matter search experiment. In this talk, I will present the first dark matter search results from XENON1T. Details about the XENON1T detector as well as the data analysis techniques will also be covered.
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Condensed-Matter Physics & Materials Science Seminar
"A model of chiral spin liquids with tunable edge states"
Presented by Christopher Mudry, Paul Scherrer Institute, Switzerland
Thursday, June 15, 2017, 1:30 pm
Bldg. 734, ISB Conference Room 201 (upstairs)Hosted by: Alexei Tsvelik
We construct a quantum field theory in (2+1)-dimensional spacetime for strongly interacting Majorana fields that is amenable to a mean-field approximation. The mean-field phase diagram predicts the existence of two competing phases, one of which supports chiral non-Abelian topological order, while the other supports chiral Abelian topological order. The two mean-field phases are separated by a continuous phase transition. This quantum field theory captures the low-energy physics of quantum spin-1/2 localized on the sites of a lattice whose interactions are $SU(2)$ symmetric but break time-reversal symmetry. The lattice geometry can be interpreted as a one-dimensional stacking of two-leg ladders or as a bilayer of two square lattices. Both incompressible ground states can thus be thought of as chiral spin liquids in two-dimensional space supporting non-Abelian and Abelian topological order, respectively.
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Particle Physics Seminar
"Hadronically interacting Dark Matter, and a new mechanism for the Baryon Asymmetry, within QCD"
Presented by Professor Glennys Reynolds Farrar, NYU
Wednesday, June 14, 2017, 10 am
Small Seminar Room, Bldg. 510Hosted by: Xin Qian
There may be a so-far-undiscovered neutral, stable particle composed of 6 quarks, denoted S, with mass m_S ~ 2 m_p. If so, the S is an excellent Dark Matter candidate. More generally, I will discuss how hadronic-strength interaction between DM and baryons can cause local DM to co-rotate with gas and stars, resulting in DM energy deposits below threshold for direct detection. DM-baryon interactions cause rotation curves to reflect baryonic density profiles, as observed in some galaxies, and can help alleviate some of the issues with CDM at small scales. An open question is whether the measured Ly-alpha power spectrum places an upper limit on the DM-baryon cross section, which is sufficiently robust and constraining to rule out the co-rotation scenario. The S-DM scenario suggests a new mechanism for producing the observed baryon asymmetry, and appears capable of naturally explaining the DM to baryon ratio.
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Physics Colloquium
"Stable Sexaquark as Dark Matter"
Presented by Professor Glennys Reynolds Farrar, NYU
Tuesday, June 13, 2017, 3:30 pm
Small Seminar Room, Bldg. 510Hosted by: Xin Qian
Dark Matter could be composed of an as-yet-undiscovered stable or essentially stable, neutral B=2 hadron composed of uuddss quarks. How such a particle, designated S for Sexaquark and to distinguish from the loosely bound di-Lambda called H-dibaryon, can be compatible with current knowledge is explained. The S is absolutely stable if m_S < 2 m_p+ 2 m_e. If m_S > 2 m_p+ 2 m_e but < m_p+m_e + m_Lambda, its lifetime could be longer than the age of the Universe. Experiments are proposed to discover and measure the mass of the proposed particle. To first approximation it behaves like standardl Cold Dark Matter, but some distinctive differences may help explain some puzzles about DM at galactic scales.
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Nuclear Theory/RIKEN Seminar
"Gluon structure of hadrons and nuclei"
Presented by Phiala Shanahan, MIT
Friday, June 9, 2017, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Heikki Mantysaari
I will present the results of recent lattice QCD studies of the gluon generalised form factors of both hadrons and light nuclei. The generalised transversity gluon distributions are of particular interest since they are purely gluonic; they do not mix with quark distributions at leading twist. In light nuclei they moreover provide a clean signature of non-nucleonic degrees of freedom. The goal of these studies is to provide QCD predictions to be tested at an electron-ion collider (EIC) designed to access gluon structure quantities including transverse-momentum dependent distributions (TMDs) and gluon generalised parton distributions (GPDs).
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Nuclear Physics Seminar
"Anatomy of Azimuthal Angle Correlations in Large and Small Systems - Why the fuss?"
Presented by Roy Lacey, Stony Brook University
Tuesday, June 6, 2017, 11 am
Small Seminar Room, Bldg. 510Hosted by: Oleg Eyser
Azimuthal momentum anisotropy measurements are ubiquitous at both RHIC and the LHC. However, there are pervasive misconceptions as to the mechanistic origin of this anisotropy in both small and large systems. In this talk, I will demonstrate how recent momentum anisotropy measurements, for a broad range of systems, have been leveraged to gain new mechanistic insights and to constrain the properties of the medium produced in these collisions. In particular, the role of final state effects versus initial state momentum domain effects in explanations of the measurements will be addressed.
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Nuclear Theory/RIKEN Seminar
"Hydrodynamic Fluctuations in Heavy Ion Collisions"
Presented by Derek Teaney, Stony Brook
Friday, June 2, 2017, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Heikki Mantysaari
We develop a set of kinetic equations for hydrodynamic fluctuations which are equivalent to nonlinear hydrodynamics with noise. The hydrokinetic equations can be coupled to existing second-order hydrodynamic codes to incorporate the physics of these fluctuations. We use the hydrokinetic equations to analyze thermal fluctuations for a Bjorken expansion, evaluating the contribution of thermal noise from the earliest moments and at late times. In the Bjorken case, the solution to the kinetic equations determines the coefficient of the first fractional power of the gradient expansion $ \sim 1/(\tau T)^{3/2}$ for the expanding system. Numerically, we find that the contribution to the longitudinal pressure from hydrodynamic fluctuations is larger than second-order hydrodynamics for typical medium parameters used to simulate heavy ion collisions. Subsequently we analyze the behaviour of hydrodynamic fluctuations of near the QCD critical point, and dilineate the relevance Kiblle-Zurek scaling relative to other physics. If time permits we will also describe how thermal fluctuations place a lower bound on the bulk viscosity of QCD. References: Y.~Akamatsu, A.~Mazeliauskas and D.~Teaney, ``A kinetic regime of hydrodynamic fluctuations and long time tails for a Bjorken expansion,'' [arXiv:1606.07742 [nucl-th]]. Y.~Akamatsu, D. Teaney, F. Yan, Y. Yin, ``Transitting the critical point,'' in progress.
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Environmental & Climate Sciences Department Seminar
"Cloud radiative fraction: Determination by high resolution photography from the surface looking upward"
Presented by Stephen E. Schwartz, Environmental & Climate Sciences Department
Thursday, June 1, 2017, 11 am
Conference Room Bldg 815EClouds greatly affect short- and longwave radiation transfer in the atmosphere and consequently climate. Hence it is essential that the amount and radiative influences of clouds be accurately represented in climate models. The conventional measure of the amount of cloud in a grid cell is cloud fraction, CF, the fraction of the surface area covered by cloud. CF is a commonly reported meteorological quantity, with a long record of surface observations, greatly augmented in the past several decades by satellite observations. Global cloud fraction determined from satellite measurements has systematically increased with time, a consequence not of secular increase in cloud fraction but of an increase with time in the sensitivity of active and passive satellite instruments. Such a situation raises the question of whether CF can be defined and how well it can be measured. Commercially available digital cameras provide an unprecedented opportunity for detailed study of cloud structure from the surface, looking upward. Key attributes of such cameras include large number of pixels, (e.g., 3456 x 4608; 16 M pixel) yielding rich detail of spatial structure, high spatial resolution, and high dynamic range (16 bit in each of three color channels at visible wavelengths). In the work reported here two cameras were pointed vertically, typically with field of view FOV 21 × 29 mrad and 120 × 160 mrad, respectively, denoted here narrow field of view, NFOV, and wide field of view WFOV, corresponding, for cloud base at 1 km, to 21 × 29 m (NFOV) and 120 × 160 m (WFOV). For perspective, the FOV for the NFOV camera is 2 × 3 sun diameters and for the WFOV camera 11 × 15 sun diameters. Nominal angular dimension of a single pixel is 6 μrad for the NFOV camera and 34 μrad for the WFOV camera, corresponding, again for cloud height 1 km, to 6 mm and 34 mm, respectively. Such single-pixel resolution is some 3 to 5 orders of magnitude finer than that avai
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Particle Physics Seminar
"Higgs boson properties: what we learn from run II of LHC"
Presented by Andrei Gritsan, Johns Hopkins University
Thursday, May 25, 2017, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Alessandro Tricoli
During the second run in 2015-2016, LHC delivered the number of proton-proton collisions far beyond expectation and at higher energy than in run I. We will review the very first results on the H boson properties based on the full dataset collected by CMS by now. We will go through the four main topics: H boson couplings to gauge bosons, couplings to fermions, self-couplings, and search for an extended Higgs sector. Prospects of some of these measurements through the end of run III and phase II of LHC will be discussed.
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RIKEN Lunch Seminar
"Mixed Anomaly and Global Consistency"
Presented by Yuya Tanizaki, RBRC
Thursday, May 25, 2017, 12:30 pm
Building 510, Room 2-160Hosted by: Hiromichi Nishimura
Symmetry and topology are powerful tools to study strongly interacting dynamics. In this talk, we will see that mixed 't Hooft anomaly and global consistency strongly constrains the possible low-energy dynamics in a simple quantum mechanical example. I will briefly explain the same idea is useful to study the phase diagram of bifundamental gauge theories at finite theta angles.
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Nuclear Physics Seminar
"Searching for collectivity and testing the limits of hydrodynamics: results from the 2016 d+Au beam energy scan"
Presented by Ron Belmont, University of Colorado Boulder
Tuesday, May 23, 2017, 11 am
Small Seminar Room, Bldg. 510Hosted by: Jin Huang
The standard picture of heavy ion collisions is that large systems (collisions of large nuclei like Au+Au and Pb+Pb) create a quark-gluon plasma that exhibits collective behavior indicative of nearly inviscid hydrodynamical evolution. Recently, data from small systems (collisions of a small projectile and a large target like d+Au and p+Pb) have been found to exhibit strikingly similar evidence for collective behavior. To further elucidate these results, RHIC delivered in 2016 a beam energy scan of d+Au collisions at 4 different energies: 200, 62.4, 39, and 19.6 GeV. In this talk we present a wide array of results from the Run16 d+Au BES and discuss the implications for collective behavior and the limits of applicability for hydrodynamics.
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Particle Physics Seminar
"Tiny Bubbles in the Mine: New Results from the PICO-60 Dark Matter Detector"
Presented by Dr. Eric Dahl, North Western
Friday, May 19, 2017, 10 am
Small Seminar Room, Bldg. 510Hosted by: Xin Qian
The PICO Collaboration builds bubble chambers for the direct detection of WIMP dark matter. These devices are unique among direct detection experiments both in the WIMP models they can probe and the backgrounds they face. The PICO collaboration has set consecutive world-leading direct-detection limits on the spin-dependent WIMP-proton cross section, most recently with a zero-background 1.2 ton-day exposure with a C3F8 target in the PICO-60 detector at SNOLAB. This result is significant not just because it reaches new WIMP parameter space, but also because it demonstrates our ability to eliminate the anomalous bubble nucleation background that limited past bubble chamber WIMP searches, opening the door for experiments at the ton scale and beyond. I will describe this new result from PICO, our immediate plans for new detectors at SNOLAB, and the broader role bubble chambers will play in the future of dark matter detection, including the new scintillating bubble chamber technology developed by my group at Northwestern.
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Physics Colloquium
"Direct Detection of sub-GeV Dark Matter"
Presented by Rouven Essig, Stony Brook University
Tuesday, May 16, 2017, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Andrei Nomerotski
Dark matter makes up 85% of the matter in our Universe, but we have yet to learn its identity. A broad array of search strategies are needed to probe for non-gravitational interactions between dark matter and ordinary matter. While most searches focus on Weakly Interacting Massive Particles (WIMPs) with masses between 1 GeV and 1 TeV, it is imperative to also consider other motivated dark matter candidates. In this talk, I will discuss dark matter with MeV-to-GeV masses, which is a theoretically and phenomenologically appealing possibility and presents a new frontier in the search for dark matter. I will highlight novel dark matter direct-detection strategies that can probe this under-explored mass range. I will describe how XENON10 data already probes dark matter with masses as low as a few MeV, and discuss improvements expected from new experiments using semiconductors or scintillators. This includes SENSEI, a new ultra-low-threshold silicon CCD detector, which is poised to probe vast new regions of parameter space in the next few years. I will also present a few simple benchmark models of MeV-to-GeV dark matter, and contrast direct-detection probes with searches at colliders and fixed-target experiments.
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Condensed-Matter Physics & Materials Science Seminar
"Thin-Film Alchemy: Using Epitaxial Engineering to Unleash the Hidden Properties of Oxides"
Presented by Darrell G. Schlom, Cornell University
Monday, May 15, 2017, 1:30 pm
Bldg. 734, ISB Conference Room 201 (upstairs)Hosted by: Ivan Bozovic
Guided by theory, unparalleled properties—those of hidden ground states—are being unleashed by exploiting large strains in concert with the ability to precisely control dimensionality and stabilize metastable phases in epitaxial oxide heterostructures. For example, materials that are not ferroelectric or ferromagnetic in their unstrained state can be transmuted into materials that are both at the same time. Similarly, new tunable dielectrics with unparalleled performance have been created as well as a new single-phase multiferroic material where ferroelectricity and strong magnetic ordering are coupled near room-temperature. These are just three examples of the unparalleled properties—those of hidden ground states—being unleashed in epitaxial oxide heterostructures utilizing thin film alchemy
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NSLS-II Friday Lunchtime Seminar Series
"Status of SSRF and the Shanghai X-FEL Projects, and Efforts in Single Particle Imaging and Whole Cell Imaging with X-FELs"
Presented by Thomas Earnest, Shanghai Synchrotron Radiation Facility
Friday, May 12, 2017, 12 pm
NSLS-II Bldg 743 (LOB 3), room 156Hosted by: Ben Ocko and Shirish Chodankar
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Nuclear Theory/RIKEN Seminar
"Probing nucleon substructure with Bayesian parameter estimation"
Presented by Scott Moreland, Duke
Friday, May 5, 2017, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Heikki Mantysaari
Multi-particle correlations observed in small collision systems at top LHC energies exhibit signatures which are similar to those observed in large collision systems and generally attributed to the formation of a deconfined quark-gluon plasma (QGP). This suggests that even proton-proton and proton-lead collisions may produce small droplets of QGP which translate spatial inhomogeneities into final-state momentum anisotropies. A primary challenge in testing hydrodynamic descriptions of small collision systems is in modeling the initial stages of the collision. In this talk, I discuss recent efforts to apply Bayesian methodology to parametric descriptions of initial state physics. I show that such methods can be extended to smaller length scales which include partonic degrees of freedom and glean information regarding the fluctuating nature of the proton.
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Computational Science Initiative Event
"Frontiers for High Performance Computing in Cancer Research"
Presented by Dr. Eric A. Stahlberg, Frederick Nat Lab for Cancer Research
Friday, May 5, 2017, 10 am
Seminar Room, Bldg. 725Hosted by: Frank Alexander
Anticipated advances in high-performance computing are enabling exciting new areas of computational and data oriented cancer research. These frontiers are being explored in a unique collaboration between the US Department of Energy and the National Cancer Institute in the Joint Design of Advanced Computing Solutions for Cancer. While the three-year collaboration is still in its first year, the collaboration is providing tremendous insight into the promise and challenges of employing extreme scale computing to advance research in the challenging and complex problem of cancer. Challenged with the aim of providing predictive insight in areas such as tumor response to treatments, molecular level interactions, and even clinical outcomes, the collaborative effort advances the frontiers of cancer research and computing in both numerically-intensive and data-intensive applications, while providing insights into opportunities for the high-performance computing community overall.
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Particle Physics Seminar
"New MEG Results and Prospects for Improved Searches for Muon and Electron Number Violation in the Charged Sector"
Presented by William Molzon, University of California, Irvine
Thursday, May 4, 2017, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Xin Qian
Searches for muon and electron number violation in the charged sector continue to be a sensitive probe of non Standard Model physics. I will give results of the full data-set of the MEG collaboration's search for muons decaying to electron plus photon and describe improvements to the MEG muon beam and apparatus that will improve sensitivity by a factor of ten in the next few years. I will also briefly review other experiments in the planning and early construction phases that are expected to improve sensitivity in related processes in the coming 5-10 years.
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Condensed-Matter Physics & Materials Science Seminar
"Transient Dynamics of Strongly Correlated Electrons After Sudden Excitations"
Presented by Marco Schiro, Institut de Physique Theorique (IPhT), CEA, Saclay, France
Thursday, May 4, 2017, 1:30 pm
Bldg. 734, ISB Conference Room 201 (upstairs)Hosted by: Robert Konik
The development of pump-probe spectroscopies with femtosecond time resolution, which allows to track the dynamics of electronic degrees of freedom in solids under optical excitations, opens up a new window to understand strongly correlated materials and offers the intriguing possibility of controlling their properties with light, on ultra-fast time scales. Triggered by these advances, the interest around time dependent phenomena in quantum many body systems has recently substantially grown. In this talk will review recent progress in understanding transient dynamics of electrons in correlated metals, Mott Insulators and superconductors. I will show that quite generically these systems display very sharp dynamical transitions as a function of the external perturbation, in correspondence of which the lattice response and the sensitivity to density inhomogeneities can be greatly enhanced.
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RIKEN Lunch Seminar
"Lattice study of gauge theory with multiple fermion representations"
Presented by Ethan Neil, University of Colorado, Boulder and RBRC
Thursday, May 4, 2017, 12:30 pm
Building 510, Room 2-160Hosted by: Enrico Rinaldi
"There is long-standing theoretical interest in the behavior of a strongly-coupled gauge theory in the presence of multiple fermions charged under different representations of the gauge group. In addition to the question of whether generation of dynamically separated scales will occur, such theories appear commonly in UV realizations of composite Higgs models with partially composite top quarks. I will present a first lattice study of SU(4) gauge theory with fermions in each of the two lowest-lying representations, discussing the finite-temperature phase structure and low-lying spectrum. Connections to BSM physics through a particular composite Higgs model will also be made."
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Nuclear Theory/RIKEN Seminar
"Analyticity in Spin and Causality in Conformal Theories"
Presented by Simon Caron-Huot, McGill
Friday, April 28, 2017, 2 pm
Large Seminar Room, Bldg. 510Hosted by: Heikki Mantysaari
The conformal bootstrap aims to calculate scaling dimensions and correlation functions in various theories, starting from general principles such as unitarity and crossing symmetry. I will explain that local operators are not independent of each other but organize into analytic functions of spin, and I will present a formula, extending a classic one due to Froissart and Gribov in the early days of Regge theory, which quantifies the consequences of this fact. Applications will include a new way to solve crossing symmetry at large spin, as well as new bounds encoding bulk locality in theories with a gravity dual. Based on 1703.00278.
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Condensed-Matter Physics & Materials Science Seminar
"Spin-liquids in novel triangular and kagome rare-earth magnets"
Presented by Martin Mourigal, Georgia Tech
Friday, April 28, 2017, 1:30 pm
Bldg. 734, ISB Conference Room 201 (upstairs)Hosted by: Igor Zaliznyak
Insulating magnets combining the effects of geometrical frustration with strong spin-orbit coupling offer a prime route to realize correlated quantum states with exotic ground-states and excitations. Spin-space anisotropy and bond-directional magnetic exchange interactions are naturally present in rare-earth oxides. One of the most celebrated consequence is the existence of classical and quantum "spin-ice" physics in rare-earth pyrochlores, materials in which magnetic ions occupy a three-dimensional network of corner-sharing tetrahedra. In this talk, I will present the discovery of distinct flavors of exotic magnetic matter in families of rare-earth oxides with two-dimensional kagome [1] and triangular [2] geometries. This experimental work relies on recent advances in materials synthesis and combines thermodynamic characterization with state-of-the-art neutron scattering experiments to unravel the classical or quantum nature of these newly discovered quasi-two-dimensional spin-liquids. [1] Emergent order in the kagome Ising magnet Dy3Mg2Sb3O14, J. A. M. Paddison, H. S. Ong, J. O. Hamp, P. Mukherjee, X. Bai, M. G. Tucker, N. P. Butch, C. Castelnovo, M. Mourigal, and S. E. Dutton, Nature Communications 7, 13842 (2016). [2] Continuous excitations of the triangular-lattice quantum spin liquid YbMgGaO4, J. A. M. Paddison, M. Daum, Z. L. Dun, G. Ehlers, Y. Liu, M. B. Stone, H. D. Zhou, and M. Mourigal, Nature Physics AOP (2016).
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Condensed-Matter Physics & Materials Science Seminar
"Magnetometry Study of Underdoped Cuprate YBa2Cu3O6.55"
Presented by Fan Yu, University of Michigan
Friday, April 28, 2017, 11 am
Bldg. 734, ISB. Conf. Rm. 168Hosted by: Qiang Li
This talk would be focused on my study of the phase diagram of underdoped cuprate YBa2Cu3O6.55 using torque magnetometry as well as my exploration of extending magnetometry method into even higher magnetic fields (>45T) using pulsed magnet. The complex phase diagrams of cuprates are sometimes referred to as "competing orders", where a large variety of ordering tendencies are known to (co-)exist. Our experiment managed to reveal an anomaly on the magnetic susceptibility, which we believe was related to charge density wave transition. Particularly interesting is that this anomaly is observed in the strong diamagnetic regime where vortex liquid exists. We believe this should be considered as a direct experimental evidence for the picture of "competing orders". To further our understanding of the quantum vortex liquid, experiments at mK temperatures and at magnetic field exceeding 40 Tesla are necessary. During my PhD study, considerable amount of time was devoted to developing a reliable magnetometry method utilizing the pulsed magnet at NHMFL, Los Alamos. I would like to present my trail-and-error as well as the proposition of "time-delayed probe design", which should be able to bypass the inherent noise of a pulsed environment.
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Particle Physics Seminar
"CP violation in neutrino oscillations and impact of new physics"
Presented by Dr. Poonam Mehta
Friday, April 28, 2017, 10 am
Small Seminar Room, Bldg. 510Hosted by: Xin Qian
The study of CP violation addresses fundamental questions such as - are the laws of physics the same for matter and anti-matter. CP is a discrete symmetry of nature given by a product of two quantities : charge conjugation (C) and parity (P). Detecting leptonic CP violation is one of the most challenging goals in particle physics today. An attractive possibility to measure CP phase is via long baseline accelerator experiments such as Deep Underground Neutrino Experiment (DUNE). In this talk, we will show that clean extraction of CP violating phase becomes a formidable task in presence of new physics and one needs to devise ways to distinguish between standard paradigm and the new physics scenarios.
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Physics Colloquium
"Current Status of Neutrinoless Double Beta Decay Research"
Presented by Bob McKeown, Jefferson Lab
Tuesday, April 25, 2017, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Andrei Nomerotski
The observation of neutrinoless double beta decay would establish that neutrinos are Majorana fermions and would represent a discovery of profound importance: that lepton number is not conserved. There is currently a worldwide effort to search for neutrinoless double beta decay, using a variety of candidate isotopes and detector technologies. A subcommittee of the Nuclear Science Advisory Committee (NSAC) recently surveyed the field and the associated research and development needs. Based on the information provided to this subcommittee, I will present an overview of the present activity in this field and the prospects for the future.
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Nuclear Theory/RIKEN Seminar
"Forward particle production in pA: implementing the NLO hybrid formalism"
Presented by Tuomas Lappi, University of Jyväskylä
Friday, April 21, 2017, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Heikki Mantysaari
Single inclusive particle production cross sections in high energy hadron collisions at forward rapidity are an important benchmark process for the CGC picture of small x QCD. The process can be calculated in the "hybrid formalism", where a collinear large-x quark or gluon scatters off the dense color field of the target. Recent calculations at next-to-leading order in perturbation theory have not led to a stable physical result for the single inclusive cross section at high transverse momenta. The problem with these NLO calculations lies in the subtraction procedure for the soft "rapidity" divergence which must be absorbed into BK renormalization group evolution of the target. This talk discusses recent work to understand and resolve the problems with the subtraction procedure. In particular, we have recently implemented numerically the quark channel production cross section using a new rapidity factorization procedure proposed by Iancu et al. For a fixed coupling one does indeed obtain a physically meaningful cross section which is positive and reduces in a controlled way to previous leading order calculations. However, it is not yet clear how to generalize this to running coupling in a way that is fully consistent with previous leading order calculations in coordinate space.
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Particle Physics Seminar
"Searching for Our Milky Way's Dark Companions"
Presented by Alex Drlica- Wagner, Fermilab
Thursday, April 20, 2017, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Erin Sheldon
Our Milky Way galaxy is surrounded by a multitude of dwarf satellite galaxies. They are some of the oldest, least luminous, most metal poor, and most dark-matter-dominated objects known. These extreme objects provide a unique opportunity for testing the standard models of cosmology and galaxy formation. In addition, the relative proximity and large dark matter content of dwarf galaxies make them excellent systems for probing the fundamental properties of dark matter. Over the past two years, the unprecedented sensitivity of the Dark Energy Camera has allowed us to nearly double the known population of Milky Way satellites. These discoveries help address the "missing satellites problem" and can be used to test the particle nature of dark matter. However, they also raise new questions concerning the role of the Magellanic Clouds in the formation of the Milky Way's satellite population. I will summarize recent results, outstanding questions, and upcoming advances in the study of the Milky Way's dark companions.
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Condensed-Matter Physics & Materials Science Seminar
"Unpaired Spins in Superconductors: From Assassin to Enabler"
Presented by Jeffrey Lynn, NIST Center for Neutron Research, National Institute of Standards and Technology
Thursday, April 20, 2017, 1:30 pm
Bldg. 734, ISB Conference Room 201 (upstairs)Hosted by: Igor Zaliznyak
The magnetic properties of superconductors have a rich and interesting history, and we will briefly review some highlights. Early work showed that even tiny concentrations of magnetic impurities destroyed the superconducting pairing through the exchange-driven spin depairing mechanism, prohibiting any possibility of magnetic order coexisting with superconductivity. The first exceptions to this rule were provided by the cubic rare-earth substituted CeRu2 alloys, followed by the ternary Chevrel-phase superconductors (e.g. HoMo6S8) and related compounds, where long range magnetic order coexists or competes with superconductivity. The very low magnetic ordering temperatures (~1 K) suggested that dipolar rather than exchange interactions dominate, thus (it was thought) allowing the coexistence. These materials also provided the first examples of the competition between ferromagnetism and superconductivity. In the newer borocarbide class of magnetic superconductors (e.g. ErNi2B2C), however, it became clear that the magnetic order is in fact exchange driven. The borocarbides also provided the first example of the spontaneous formation of flux quanta (vortices). For the cuprate and iron-based superconductors (formerly known as "high Tc") we now have come full circle, as the spins are not only tolerated but are intimately tied to the superconductivity. The "parent" cuprate systems are Mott-Hubbard antiferromagnetic insulators with very strong magnetic interactions that are two-dimensional in nature. These strong exchange interactions survive into the superconducting state, yielding highly correlated electrons that participate directly in the superconducting pairing. The "parent" materials of the new iron-based high TC superconductors are also antiferromagnets with very energetic spin excitations, and in the superconducting regime they form a "magnetic resonance" that is directly tied to the superconducting order parameter, ju
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Condensed-Matter Physics & Materials Science Seminar
"Listening to the hydrodynamic noise of Dirac fluid in graphene"
Presented by Kin Chung Fong, Raytheon BBN Technologies and Harvard University
Tuesday, April 18, 2017, 1:30 pm
Bldg. 734, ISB Conference Room 201 (upstairs)Hosted by: Qiang Li
Interactions between the Dirac fermions in graphene can lead to new collective behavior described by hydrodynamics. By listening to the Johnson noise of the electrons, we are able to probe simultaneously the thermal and electrical transport of the Dirac fluid and observe how it departs from Fermi liquid physics. At high temperature near the neutrality point, we find a strong enhancement of the thermal conductivity and breakdown of Wiedemann-Franz law in graphene. This is attributed to the non-degenerate electrons and holes forming a strongly coupled Dirac fluid. At lower temperatures beyond the hydrodynamic behavior, the Dirac fermions are in extreme thermal isolation with minute specific heat that can be exploited for ultra-sensitive photon detection. We will present our latest experimental result towards observing single microwave photons and explore its role in scaling up the superconducting qubit systems. Our model suggests the graphene-based Josephson junction single photon detector can have a high-speed, negligible dark count, and high intrinsic quantum efficiency for applications in quantum information science and technologies. Ref: Science 351, 1058 (2016)
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Nuclear Physics Seminar
"Search for the Chiral Magnetic Effect at RHIC : challenges and opportunities"
Presented by Prithwish Tribedy, BNL
Tuesday, April 18, 2017, 11 am
Small Seminar Room, Bldg. 510Hosted by: Jia Jiangyong
In this talk I will discuss about the ongoing and future efforts at RHIC towards the search for the Chiral Magnetic Effect (CME). I will focus on the recent STAR measurements of the charge separation across the reaction plane, a predicted signal of the Chiral Magnetic Effect. Although charge separation has been observed, it has been argued that the measured separation in A+A collisions can be explained by elliptic flow related backgrounds. I will discuss on the challenges in disentangling such background contributions from the signals of CME. I will also discuss on implications of the recent measurements of charge separation in p+A collisions towards the search for CME.
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Nuclear Theory/RIKEN Seminar
"Effect of magnetic field on flow fluctuations in"
Presented by Ajit M. Srivvastava
Friday, April 14, 2017, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Heikki Mantysaari
Very strong magnetic fields can arise in non-central heavy-ion collisions at ultrarelativistic energies, which may not decay quickly in a conducting plasma. We carry out magnetohydrodynamics simulations to study the effects of this magnetic field on the evolution of the plasma and on resulting flow fluctuations. Our results show that magnetic field leads to enhancement in elliptic flow, while flow fluctuations lead to reorganization of magnetic flux resulting in a transient increase in the local magnetic field. We also show generation of vorticity arising from nontrivial dependence of magnetosonic waves on pressure gradients and magnetic field direction. Magnetic field from collision of deformed nuclei shows very nontrivial features and can lead to qualitatively new effects on plasma evolutions. We discuss possibility of dynamo effect in the presence of vortices if any exotic high baryon density QCD phases are achieved in heavy-ion collisions.
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Particle Physics Seminar
"Natural Seesaw in Warped/Composite Higgs framework and its LHC Signals"
Presented by Kaustubh Agashe, University of Maryland
Thursday, April 13, 2017, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Christoph Lehner
I will show how a natural seesaw model for SM neutrino mass arises within the general framework of a warped extra dimension (dual to composite Higgs in 4D). It starts out as an attempt at implementing the high-scale seesaw mechanism. I will first carefully determine what the underlying dynamical picture really is. Motivated by this physical understanding, LHC signals of TeV-mass SM singlet neutrinos within a specific model for the electroweak gauge sector will be discussed. Some of these channels are similar to those studied in 4D left-right (LR) symmetric models, but nonetheless the two can be distinguished. While other signals are more characteristic of the 5D/composite framework, i.e., are absent in 4D LR models.
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Condensed-Matter Physics & Materials Science Seminar
"Electronic Squeezing of Pumped Phonons: Negative $U$ and Transient Superconductivity"
Presented by Dante Kennes, Columbia University
Thursday, April 13, 2017, 1:30 pm
Bldg. 734, ISB Conference Room 201 (upstairs)Hosted by: Neil Robinson
Advances in light sources and time resolved spectroscopy have made it possible to excite specific atomic vibrations in solids and to observe the resulting changes in electronic properties but the mechanism by which phonon excitation causes qualitative changes in electronic properties has remained unclear. Here we show that the dominant symmetry-allowed coupling between electron density and dipole active modes implies an electron density-dependent squeezing of the phonon state which provides an attractive contribution to the electron-electron interaction, independent of the sign of the bare electron-phonon coupling and with a magnitude proportional to the degree of laser-induced phonon excitation. Reasonable excitation amplitudes lead to non-negligible attractive interactions that may cause significant transient changes in electronic properties including superconductivity. The mechanism is generically applicable to a wide range of systems, offering a promising route to manipulating and controlling electronic phase behavior in novel materials.
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Nuclear Physics Seminar
"Systematic study of hadron production in highly asymmetric collisions at PHENIX"
Presented by Norbert Novitzky, Stony Brook University
Tuesday, April 11, 2017, 11 am
Small Seminar Room, Bldg. 510Hosted by: Jin Huang
The observation of long range correlations in highly asymmetric systems as in p+Pb and d+Au collisions suggests the creation of a medium with collective behavior. Single particle production has proven to be a valuable tool to probe the quark-gluon plasma formed in heavy ion collisions as it is sensitive to energy loss, modifications of the nuclear wavefunction. It is an open question whether the apparent medium in small-on-large collisions and the QGP in large-on-large collisions is indeed the same, as is the role of the dynamics of the projectile (nucleon) wavefunction. In order to address these questions with a systematic study of highly asymmetric collisions, the RHIC collider provided beams for p+Al, p+Au, d+Au and 3He+Au collisions. The hadron production as a function of transverse momentum (pT) and rapidity can provide us very useful information about the evolution of the initial state and medium formation with system size. We will present the neutral pion and charged hadron measurements at forward, mid- and backward rapidities and discuss the implications of the results.
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Nuclear Theory/RIKEN Seminar
"Anisotropic dissipative fluid dynamics - foundations & applications in heavy-ion physics"
Presented by Professor Dirk Rischke, Johann Wolfgang Goethe-Universität
Friday, April 7, 2017, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Heikki Mantysaari
In collisions of heavy ions at ultrarelativistic energies, a system of hot and dense strongly interacting matter is created. This matter exhibits a surprisingly strong degree of collectivity, implying a short mean free path of its constituents and, consequently, a small shear viscosity-to-entropy density ratio. This allows to describe the evolution of the system using relativistic dissipative fluid dynamics. Dissipative fluid dynamics can be understood as an expansion around local thermodynamical equilibrium, corresponding to the ideal-fluid limit where dissipative corrections are absent. A short mean free path means that this expansion is well defined and converges sufficiently rapidly. Nevertheless, in the initial stage of a heavy-ion collision, space-time gradients of the fluid-dynamical fields (energy-momentum and net-charge densities) are so large that dissipative corrections to the ideal-fluid limit can become sizable. In this situation, novel approaches to relativistic dissipative fluid dynamics are called for. One such approach is anisotropic dissipative fluid dynamics, which is based on an expansion around an anisotropic non-equilibrium state (instead of local thermodynamical equilibrium, as in conventional dissipative fluid dynamics). In this talk, I present a derivation of the equations of motion of anisotropic dissipative fluid dynamics from the Boltzmann equation, using the method of moments. I also discuss how to resolve an ambiguity to close the system of equations of motion in the case when there are no corrections to the anisotropic state which constitutes the basis of the moment expansion.
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Instrumentation Division Seminar
"Next Generation Readout Electronics: Highly Integrated, High Performance and Low Cost Data Acquisition for Future Instrumentation Needs"
Presented by Isar Mostafanezhad, Nalu Scientific, LLC
Thursday, April 6, 2017, 2:30 pm
Large Conference Room, Bldg. 535In this presentation, we discuss recent progress in high channel count data acquisition systems for large experiments. In recent years Nalu Scientific has established a new model for integration of readout electronics with detectors for HEP/NP applications. The most recent work has been involvement in the commissioning of the Belle II Time of Propagation Klong and Muon subdetectors at KEK in Japan. These innovations resulted in modern, modular, compact and high performance readout systems. Nalu Scientific, under multiple SBIR awards, has been working to commercialize these technologies to become available as off-the-shelf products for future experiments. We will cover: 1. Summary of Belle II TOP PID and KLM subdetectors 2. High performance, highly integrated, low cost readout 3. Current efforts in high resolution/ high performance timing 4. Specialized compact readout electronics for SiPMs
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A Special HET/RIKEN Lunch Seminar
"The Road to Nuclear Physics from Standard Model"
Presented by Zohreh Davoudi, MIT
Thursday, April 6, 2017, 12:30 pm
Building 510, Room 2-160Hosted by: Hiromichi Nishimura
At the core of nuclear physics is to understand complex phenomena occurring in the hottest and densest known environments in nature, and to unravel the mystery of the dark sector and other new physics possibilities. Nuclear physicists are expected to predict, with certainty, the reaction rates relevant to star evolutions and nuclear energy research, and to obtain the "standard" effects in nuclei to reveal information about the "non-standard" sector. To achieve such certainty, the field has gradually started to eliminate its reliance on the phenomenological models and has entered an era where the underlying interactions are "effectively" based on the Standard Model of particle physics, in particular Quantum Chromodynamics (QCD). The few-nucleon systems can now emerge directly from the constituent quark and gluon degrees of freedom and with only QCD interactions in play, using the numerical method of lattice QCD. Few-body observable, such as few-nucleon interactions and scattering amplitudes, as well transition amplitudes and reaction rates, have been the focus of this vastly growing field, as once obtained from QCD, and matched to effective field theories, can advance and improve the nuclear many-body calculations of exceedingly complex systems. This talk is a brief introduction to this program and its goals, with a great focus on the progress in few-body observables from QCD.
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HET Seminar
"Hints of New Physics in Semi-leptonic B-meson Decays"
Presented by Diptimoy Ghosh, Weizman
Wednesday, April 5, 2017, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Amarjit Soni
In recent years, a number of interesting signals of potential new physics in semi-leptonic B-meson decays have been reported both by the B-factories as well as the LHCb. In this talk, I will discuss these observations with a particular emphasis on the observable $R_{D^*}$, the ratio of the branching fraction of $\bar{B} \to D^* \tau \bar{\nu}_\tau$ to that of $\bar{B} \to D^* \ell \bar{\nu}_\ell (\ell = \mu, e )$, which shows a 3.3 sigma deviation from the Standard Model prediction. I will present an effective field theory analysis of these potential new physics signals and discuss possible ways to distinguish the various operators.
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Nuclear Physics Seminar
"New insights to the search for the anomalous chiral effects using small colliding system at the LHC"
Presented by Zhoudunming Tu, Rice University
Tuesday, April 4, 2017, 11 am
Small Seminar Room, Bldg. 510Hosted by: Jiangyong Jia
In relativistic heavy ion collisions, anomalous chiral effects have been predicted to occur in presence of a strong magnetic field induced by the spectator protons, e.g., the chiral magnetic effect (CME) and chiral magnetic wave (CMW). In the past decade, measurements of CME and CMW have been attempted from RHIC to the LHC energies, where significant signals were found to be in line with expectations of the chiral effects. However, soon after the initial excitement, various sources of background effects were identified and proposed to qualitatively describe the data. The origin of the backgrounds has been extensively studied, but still remains inconclusive to date. Recently, novel collective phenomenon has been found in high-multiplicity pA collisions, similar to those in AA collisions. Due to the weak correlation between the magnetic field direction and the event plane, the high-multiplicity pPb data are expected to have much suppressed CME and CMW signal, comparing to that in PbPb collisions, and thus provide an ideal testing ground to observables related to the anomalous chiral effects. In this talk, I will present new measurements related to the CME and CMW from CMS in pPb and PbPb collisions at the LHC, and discuss their implications to the search for the anomalous chiral effects including an outlook for future studies.
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Instrumentation Division Seminar
"Ultrafast imaging technology: from visible light to high-energy X-ray photons"
Presented by Zhehui Wang, LANL
Friday, March 31, 2017, 2:30 pm
Large Conference Room, Bldg. 535We are now in the era of ultrafast imaging, which is the ability to observe transient events with a time duration no longer than 100 ps (one billionth of the time for eye blinking). Innovative methods have demonstrated photography at the mind-bending speed of one trillion frames per second. Several recent advances make ultrafast imaging possible: ultrashort lasers and X-rays for illumination, abilities to harvest ultrafast responses in materials for efficient photon and electron detection, innovative ways to store and process data. It will be shown that ultrafast imaging technology is a natural fit to mesoscopic science. Meanwhile, ultrafast imaging technology also permits photography of macroscopic objects around the corner or hidden away from the direct line of sight. One recent LANL interest in ultrafast high-energy X-ray imaging is driven by MaRIE. Some material challenges will be highlighted towards a GHz frame-rate burst mode camera for photons at above 30 keV energies.
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Particle Physics Seminar
"neutrinoless double beta decay and nuclear structure theory"
Presented by Professor Petr Vogel, Caltech
Friday, March 31, 2017, 11 am
Small Seminar Room, Bldg. 510Hosted by: Xin Qian
Search for the neutrinoless double beta decay is one of the main goals of nuclear physics community worldwide. If observed, it would be an example of "physics beyond the Standard Model", showing that the lepton number is not a conserved quantity and that neutrinos are massive Majorana fermions. After introducing the subject and its particle physics consequences I will concentrate on the issue of evaluation of the nuclear matrix elements. Despite decades of effort and hundreds of publications, different approaches give results that differ by roughly a factor of three, and it is difficult to decide which of them is the most realistic. I will describe the strengths and weaknesses of the nuclear models used. In addition, I will discuss the problem of "quenching", i.e. of reduction of the matrix elements of weak axial current in complex nuclei, that potentially affects the neutrinoless double beta decay matrix element values signiffcantly
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Particle Physics Seminar
"Evaluation of reactor neutrino flux: issues and uncertainties"
Presented by Professor Petr Vogel, Caltech
Thursday, March 30, 2017, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Xin Qian
Evaluation of the reactor antineutrino flux and spectrum is an essential ingredient of their application in the neutrino oscillation studies. Two anomalies, i.e. discrepancies between the observed and expected count rates, are widely discussed at the present time. The total rate is about 6% lower than the expectation at all distances > 10 m from the reactor. And there is a shoulder (often referred to as "bump") at neutrino energies 5-7 MeV, not predicted in the calculated spectrum. I review the ways the flux and spectrum is evaluated. I argue that far reaching conclusions based on these anomalies should await a thorough understanding of the uncertainties of the spectrum, and point out possible standard physics sources of the anomalies.
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Condensed-Matter Physics & Materials Science Seminar
"Explore Mesoscopic Physics in Strongly Correlated Electron Materials with IR near-field microscopy and spectroscopy"
Presented by Mengkun Liu, Stony Brook University
Thursday, March 30, 2017, 1:30 pm
ISB Bldg. 734, Conf. Rm. 201 (upstairs)Hosted by: Cedomir Petrovic
In strongly correlated electron materials, the delicate interplay between spin, charge, and lattice degrees of freedom often leads to extremely rich phase diagrams exhibiting intrinsic phase inhomogeneities. The key to understanding such complexities usually lies in the characterization and control of these materials at fundamental energy, time and length scales. I will use this opportunity to report the recent advances in the IR and THz near-field microscopy and spectroscopy, and explain how they can be used to probe electronic/structural phase transitions with unprecedented spatial and temporal resolutions. Specifically, with scanning near-field infrared microscopy we resolved the insulator to metal phase transitions in 3d (VO2), 4d (Ca2RuO4) and 4f (SmS) materials with ~10 nm resolution over a broad spectral range. The results set the stage for future spectroscopic investigations to access the fundamental properties of complex materials.
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RIKEN Lunch Seminar
"The hadronic light-by-light contribution to muon g-2 from lattice QCD"
Presented by Luchang Jin, BNL
Thursday, March 30, 2017, 12:30 pm
Building 510, Room 2-160Hosted by: Enrico Rinaldi
The current measurement of muonic g-2 disagrees with the theoretical calculation by about 3 standard deviations. Hadronic vacuum polarization (HVP) and hadronic light by light (HLbL) are the two types of processes that contribute most to the theoretical uncertainty. The current value for HLbL is still given by models. We report our latest lattice calculation of hadronic light-by-light contribution to muon g-2 using our recent developed moment method. The connected diagrams and the leading disconnected diagrams are included. The calculation is performed on a 48^3 × 96 lattice with physical pion mass and 5.5 fm box size. We expect sizable finite volume and finite lattice spacing corrections to the results of these calculations which will be estimated in calculations to be carried out over the next 1-2 years.
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Particle Physics Seminar
"Is there evidence for cosmic acceleration?"
Presented by Subir Sarkar, Oxford University
Thursday, March 30, 2017, 11 am
Small Seminar Room, Bldg. 510Hosted by: Xin Qian
The 'standard' model of cosmology is founded on the basis that the expansion rate of the universe is accelerating at present – as was inferred from the Hubble disgram of Type la supernovae. There exists now a much bigger database of supernovae so we can perform rigorous statistical tests to check whether these 'standardisable candles' indeed indicate cosmic acceleration. Taking account of the empirical procedure by which corrections are made to their absolute magnitudes to allow for the varying shape of the light curve and extinction by dust, we find that the data are still consistent with a constant rate of expansion. The implications of this will be discussed.
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Physics Colloquium
"Physics in the complex domain"
Presented by Carl Bender, Washington University
Tuesday, March 28, 2017, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Robert Pisarski
The theory of complex variables is extremely useful because it helps to explain the mathematical behavior of functions of a real variable. Complex variable theory also provides insight into the nature of physical theories. For example, it provides a simple and beautiful picture of quantization and it explains the underlying reason for the divergence of perturbation theory. By using complex-variable methods one can generalize conventional Hermitian quantum theories into the complex domain. The result is a new class of parity-time-symmetric (PT-symmetric) theories whose remarkable physical properties have been studied and verified in many recent laboratory experiments.
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Condensed-Matter Physics & Materials Science Seminar
"Thermalization and light cones in a model with weak integrability breaking"
Presented by Stefan Groha, University of Oxford, United Kingdom
Tuesday, March 28, 2017, 11 am
Bldg. 734, ISB Conference Room 201 (upstairs)Hosted by: Neil Robinson
We employ equation of motion techniques to study the non-equilibrium dynamics in a lattice model of weakly interacting spinless fermions. Our model provides a simple setting for analyzing the effects of weak integrability breaking perturbations on the time evolution after a quantum quench. We establish the accuracy of the method by comparing results at short and intermediate times to time-dependent density matrix renormalization group computations. For sufficiently weak integrability-breaking interactions we always observe prethermalization plateaux, where local observables relax to non-thermal values at intermediate time scales. At later times a crossover towards thermal behaviour sets in. We determine the associated time scale, which depends on the initial state, the band structure of the non-interacting theory, and the strength of the integrability breaking perturbation. Our method allows us to analyze in some detail the spreading of correlations and in particular the structure of the associated light cones in our model. We find that the interior and exterior of the light cone are separated by an intermediate region, the temporal width of which appears to scale with a universal power-law t 1/3.
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Nuclear Physics Seminar
"Beam energy and system dependence of anisotropic flow measurements from STAR"
Presented by Niseem Magdy, Stony Brook University
Tuesday, March 28, 2017, 11 am
Small Seminar Room, Bldg. 510Hosted by: Jin Huang
Recent STAR measurements of azimuthal anisotropy have focused on the use of two- and multi-particle correlations as probes for model constraints for the temperature dependence of the specific shear viscosity $\eta/s$ and the initial-state structure of the collision zone. We will discuss and summarize recent two- and multi-particle correlations measurements of $v_n$ $(n > 1)$ , dipolar flow $v^{even}_1$, and $\langle cos(n \varphi_{1} + m \varphi_{2} - (n+m) \varphi_{3}) \rangle$, as a function of centrality, transverse momentum ($p_T$), and pseudorapidity ($\eta$) for $Au+Au$ at ($\sqrt{s_{NN}} = 7 - 200$~GeV;{em BES-I}), $U+U$ at ($\sqrt{s_{NN}} = 193$ GeV) and $Cu+Au$ , $Cu+Cu$ ,$d+Au$ ,$p+Au$ at ($\sqrt{s_{NN}} = 200$ GeV).
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Condensed-Matter Physics & Materials Science Seminar
"Resonant Inelastic X-ray Scattering and X-ray Emission Spectroscopy of Iron Pnictide Superconductors"
Presented by Jonathan Pelliciari, Paul Scherrer Institute, Switzerland
Monday, March 27, 2017, 10 am
ISB Bldg. 734, Conf. Rm. 201 (upstairs)Hosted by: Mark Dean
I will describe Resonant Inelastic X-Ray Scattering (RIXS) experiments performed at the Swiss Light Source focusing on the detection of high-energy spin fluctuations on iron pnictides. I will show that RIXS has been successfully used to extract the spin excitation spectrum on NaFeAs, BaFe2As2, EuFe2As2 and SmFeAsO, parent compounds [1-3]. We investigated electron-doped NaFe1-xCoxAs observing the persistence of broad dispersive magnetic excitations in optimal and overdoped samples [1]. The energy of such modes is unaffected by doping and the magnetic weight per iron atom of magnons / paramagnons remains constant, demonstrating the impurity role of Co doping. The persistence of magnetic spectral weight is also caught by theoretical calculations. In the second part of the talk, I will present a combined Fe-L3 RIXS and Fe-Kβ X-rays emission spectroscopy (XES) study of isovalently doped BaFe2(As1-xPx)2 spanning a large portion of the phase diagram. RIXS measurements find the persistence of broad dispersive magnetic excitations for all doping levels. Remarkably, the energy of such modes is strongly hardened by doping differently from the cases of electron- and hole-doped BaFe2As2 [5]. On the other hand, XES experiments show a gradual quenching of the local magnetic moment, which is intriguing if compared to the behavior of spin correlations. We link the unconventional evolution of magnetism to the shift from 2- to 3-dimensional electronic structure of the system, hand in hand with the warping of the Fermi surface. Combined together these findings help to shed light on the real degree of electronic correlations in Fe pnictides. References [1] J. Pelliciari et al., Phys. Rev. B, 93, 134515 (2016); [2] J. Pelliciari et al., Appl. Phys. Lett. 109, 122601 (2016); [3] J. Pelliciari et al., "Local and collective magnetism of EuFe2As2" accepted in Phys. Rev. B (2017); [4] K. J. Zhou et al, Nat. Comm., 4, 1470 (2013)
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Nuclear Theory/RIKEN Seminar
"A solitonic approach to neutron stars: The (BPS) Skyrme model"
Presented by Carlos Naya, Durham
Friday, March 24, 2017, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Heikki Mantysaari
The Skyrme model is a low energy effective field theory of strong interactions where nuclei and baryons appear as collective excitations of pionic degrees of freedom. Proposed by Tony Skyrme in the sixties, his ideas received further support when it was discovered that in the limit of the large number of colours of QCD, an effective theory of mesons arises. In the last years, there has been a revival of Skyrme's ideas and new related models, some of them with BPS bounds (topological lower energy bounds), have been proposed. It is the aim of this talk to focus on the one known as BPS Skyrme model. After a brief introduction to this BPS limit we study its application to neutron stars where we will find that high maximal masses are supported. In addition, the BPS Skyrme model allow us to perform both mean-field and exact calculations and a comparison between both approaches will be presented.
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Particle Physics Seminar
"Neutrino Interactions with Nuclei and Long-Baseline Experiments"
Presented by Professor Ulrich Mosel, Giessen University
Friday, March 24, 2017, 10 am
Small Seminar Room, Bldg. 510Hosted by: Xin Qian
The extraction of neutrino mixing parameters and the CP-violating phase requires knowledge of the neutrino energy. This energy must be reconstructed from the final state of a neutrino-nucleus reaction since all long-baseline experiments use nuclear targets. This reconstruction requires detailed knowledge of the neutrino reactions with bound nucleons and of the final state interactions of hadrons with the nuclear environment. Quantum-kinetic transport theory can be used to build an event generator for this reconstruction that takes basic nuclear properties, such as binding, into account. Some examples are discussed that show the effects of nuclear interactions on observables in long-baseline experiments.
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Condensed-Matter Physics & Materials Science Seminar
"Nematic quantum paramagnet and possible application to FeSe"
Presented by Fa Wang, International Center for Quantum Materials Peking University, China
Thursday, March 23, 2017, 11 am
Bldg. 734, ISB Conference Room 201 (upstairs)Hosted by: Weiguo Yin
The nematic phases in iron pnictides are in close proximity to the stripe antiferromagnetic order, suggesting that magnetism is the driving force for the spontaneous 4-fold crystal rotation symmetry breaking. In contrast, bulk FeSe shows a nematic phase below 90K at ambient pressure, but has no magnetic long range order down to very low temperature. This prompts suggestions that the nematicity in FeSe is driven by some other mechanism. We argue that magnetic correlation can still drive nematic order in the absence of magnetic long-range order. By field theoretical considerations and exact diagonalization results on finite size lattices, we conclude that the paramagnetic phase in frustrated spin-1 J_1-J_2 model on square lattice is likely a "nematic quantum paramagnet", which breaks only the crystal 4-fold rotation symmetry. The prototype wavefunctions of such quantum ground states are horizontal(vertical) aligned spin-1 AKLT chains. We suggest that the local spins in FeSe may form this phase due to strong frustration. One unique consequence of this proposal is that the nematic paramagnetic phase will be close to both stripe and Neel antiferromagnetic order, and will thus host low but finite energy spin fluctuations at both ordering wavevectors. Reference: Fa Wang, S. A. Kivelson, and Dung-Hai Lee, Nat. Phys. 11, 959 (2015)
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Particle Physics Seminar
"Heavy bosons: a probe into the unknown"
Presented by Viviana Cavaliere, University of Illinois Champaign/Urbana
Wednesday, March 22, 2017, 11 am
Small Seminar Room, Bldg. 510Hosted by: Michael Begel
The large amount of high-energy proton-proton collision data at the LHC provides an unprecedented opportunity to search for new physics beyond the Standard Model at the TeV scale. The 2012 discovery of a 125 GeV Higgs boson opened a new door to understanding the universe, providing an exciting new tool to use in these searches, given it is now produced about once per second at the current collision rate. The talk will review recent ATLAS searches for physics beyond the Standard Model, focusing on the central role of processes with heavy bosons, including the Higgs, and the corresponding new possible signatures that range from spectacular new resonances to subtle changes in kinematic distributions.
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Nuclear Theory/RIKEN Seminar
"Universal Transverse Momentum Dependent Fragmentation"
Presented by Duff Neill, LANL
Friday, March 17, 2017, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Heikki Mantysaari
Fragmentation is the earliest and perhaps most interesting QCD jet observable, since it directly deals with the parton-hadron duality at the end of the QCD cascade. The most basic fragmentation observables all enjoy the property of being universal, in the sense that a sufficiently energetic parton that initiates the cascade factorizes from the rest of the event, so that the underlying soft structure of the event to a good approximation does not change the fragmentation spectrum. With the luminosities and resolution of modern detectors, we can begin to study the fragmentation process in three dimensions: both the energy spectrum and the transverse fluctuations to the collinear direction of initiating hard parton. However, when one wants to study the transverse fluctuations, one becomes very sensitive to the underlying jet definition, in particular, how the collinear direction is defined. Intuitive definitions of the jet direction, like the total momentum of the jet constituents, are inherently sensitive to soft processes, and can spoil the universality of the spectrum. I will discuss how a simple change in the jet definition removes this soft sensitivity, and allows one to study the intrinsic three dimensional structure of collinear splittings, which should be process independent.
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Particle Physics Seminar
"Search for physics beyond the SM using multijet events with the ATLAS detector at the LHC"
Presented by Haichen Wang, LBL
Thursday, March 16, 2017, 11 am
Small Seminar Room, Bldg. 510Hosted by: Michael Begel
Search for physics beyond the Standard Model (SM) has been one of the most important goals of the physics program at the Large Hadron Collider (LHC).Among all the final states, the multijet final state has long been considered as a challenging one for the search of physics beyond the SM due to its large background. Though, exciting new physics phenomena, such as the production of black hole as well as massive supersymmetric (SUSY) particles, may well result in signals in multijet final state. I present searches for physics beyond the SM using multijet events from 13 TeV collision data taken in 2015 and the first half of 2016 by the ATLAS experiment at the LHC. I focus on a search for the production of black hole and a search for massive supersymmetric particles decaying to many jets via R-Parity Violating (RPV) couplings. The two examples represent searches targeting physics beyond the SM at different mass scales, and therefore different analysis strategies are employed. These searches have greatly improved the sensitivity of the LHC to the black hole production and RPV SUSY scenarios, and they are complementary to searches using events of leptons, photons and missing transverse energy.
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Nuclear Physics Seminar
"The sPHENIX Calorimeters: a proto-type story"
Presented by Megan Connors, Georgia State University and RBRC
Wednesday, March 15, 2017, 3:30 pm
Small Seminar Room, Bldg. 510Hosted by: Jin Huang
sPHENIX, scheduled to start taking data in 2022 at RHIC, is a detector designed to probe the inner workings of the quark gluon plasma by measuring jets and their substructure, heavy flavor tagged jets and quarkonia. The design includes tracking systems, a solenoid magnet and calorimeter system. The calorimeter system, designed to measure the energy of jets, is comprised of an electromagnetic calorimeter, an inner hadronic calorimeter and and outer hadronic calorimeter. Prototypes of these detectors were built and tested in 2016. The results of the test beam show that the performance is well within the requirements set by the sPHENIX program. In addition, the results validate the GEANT4 simulation studies. The design of the sPHENIX calorimeter system, the test beam results from the calorimeter prototypes and additional studies will be presented
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Nuclear Theory Seminar
"Nuclear Matter EoS and thermodynamic Properties of Skyrme models"
Presented by Mareike Haberichter, Amherst
Friday, March 10, 2017, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Heikki Mantysaari
The Skyrme model is a candidate to describe the low energy regime of QCD where baryons and nuclei are topological excitations in a low-energy effective field theory of pions. The Skyrme model and its BPS variant (Skyrme model with a lower topological energy bound which is saturated) have been applied to the description of nuclei with notable recent success, e.g. quantitative description of Carbon-12 (including the Holye state and its rotational band) and of the low-lying energy spectrum of Oxygen-16. In this talk, we test Skyrme theories as models for nuclear matter at high densities and explore the thermodynamical properties of skyrmionic matter at zero temperature. We compute analytically the mean-field equation of state in the high and medium pressure regimes by applying topological bounds on compact domains. We identify which term in a generalised Skyrme model is responsible for which part in the equation of state and compare our findings with the corresponding results in the Walecka model. We find that the BPS submodel plays the dominant role at large densities. The BPS Skyrme model even allows us to derive thermodynamical variables and densities directly from the theory without having to perform a mean-field limit. This distinguishes the BPS Skyrme model from other models of nuclear matter where usually a mean-field limit has to be performed. Note that this is the first of two talks on Skyrme models and their predictions for nuclear matter at high densities. The second part on the description of neutron stars as Skyrme solitons will be given by Carlos Naya (Durham) on March, 24th at BNL.
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Particle Physics Seminar
"WW measurements at CMS and perspectives for the HL-LHC"
Presented by Rafael Coelho Lopes de Sa, FNAL
Thursday, March 9, 2017, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Michael Begel
We will review recent diboson measurements and searches in the WW final state performed with the CMS detector. We will discuss the perspectives for some of these measurements with the full HL-LHC dataset. We will briefly describe some of the upgrades being designed for the CMS Silicon Tracker in order to operate in the high pileup environment of the HL-LHC while maintaining excellent performance for the final states discussed in this talk.
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RIKEN Lunch Seminar
"Finite-Temperature Perturbative QCD confronts Lattice"
Presented by Thorben Graf, University of Frankfurt
Thursday, March 9, 2017, 12:30 pm
Building 510, Room 1-224Hosted by: Heikki Mantysaari
Since decades expressions for the thermodynamic potential were calculated perturbatively at finite temperature (and density) and pushed to higher orders. I review the current status of these efforts including resummation techniques and compare them to results of lattice Monte Carlo simulations and address unanswered questions. Finally, I present results for several thermodynamic quantities within the next-to-leading order calculation of the thermodynamic potential at finite T and \mu including non-vanishing quark masses.
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Condensed-Matter Physics & Materials Science Seminar
"Transport and signatures of Mottness versus Hundness in strongly correlated metals"
Presented by Xiaoyu Deng, Rutgers
Thursday, March 9, 2017, 11 am
Bldg. 734, ISB Conference Room 201 (upstairs)Hosted by: Gabi Kotliar
In this seminar I will focus two fundamental aspects of strongly correlated metals: the transport properties and the origin of correlation. Recent advances enables us to study quantitatively various properties of two archetypal correlated oxides, vanadium oxides and ruthenates, using the LDA+DMFT method. Both are strongly correlation, these two materials are quite different in their origins of correlation: V2O3 is proximate to a Mott state while Sr2RuO4 is not. Thus V2O3 is regarded as a prototype Mott system, while recent studies emphasize that Sr2RuO4 belongs to new category termed "Hund's metal" in which Hund's coupling is responsible for the correlations. We carried out a systematical theoretical study on the transport properties of V2O3 and ruthenates family. Our computed resistivity and optical conductivity are in very good agreement with experimental measurements, which clearly demonstrates that the strong correlation dominates the transport of this material , despite their origin of correlation. We demonstrated that "resilient quasiparticles" dominates the transport. Furthermore by expressing the resistivity in terms of an effective plasma frequency and an effective scattering rate, we uncover the so-called "hidden Fermi liquid" behavior. We identified signatures of Mottness and Hundness by a comparative study of V2O3 and Sr2RuO4. In V2O3 the low temperature coherent resonance emerges from the pseudogap regime appearing at high temperature between incoherent peaks, while in Sr2RuO4, it emerges from a single incoherent peak with large finite value at the Fermi level.. We show that these two contrasting scenarios features interesting behaviors in the local properties of correlated atoms including charge fluctuations, spin and orbit susceptibility and entropy. The findings shed new lights on the understanding of strongly correlated metals.
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Particle Physics Seminar
"Electroweak Physics at ATLAS"
Presented by Jake Searcy, Michigan
Wednesday, March 8, 2017, 11 am
Small Seminar Room, Bldg. 510Hosted by: Michael Begel
Electroweak symmetry breaking is a central pillar of the standard model, and experimentally one of the least understood. Many physics scenarios predict modifications to this mechanism resulting in new particles or interactions. This talk will summarize our knowledge of the electroweak sector with a particular focus on the interactions between W-bosons.
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Environmental & Climate Sciences Department Seminar
"Sub 2 nm Particle Characterization in Systems with Aerosol Formation and Growth"
Presented by Yang Wang, Washington University
Wednesday, March 8, 2017, 10 am
Conference Room Bldg 815EHosted by: Jian Wang
Aerosol science and technology enable continual advances in material synthesis and atmospheric pollutant control. Among these advances, one important frontier is characterizing the initial stages of particle formation by real time measurement of particles below 2 nm in size. Sub 2 nm particles play important roles by acting as seeds for particle growth, ultimately determining the final properties of the generated particles. Tailoring nanoparticle properties requires a thorough understanding and precise control of the particle formation processes, which in turn requires characterizing nanoparticle formation from the initial stages. This work pursued two approaches in investigating incipient particle characterization in systems with aerosol formation and growth: (1) using a high-resolution differential mobility analyzer (DMA) to measure the size distributions of sub 2 nm particles generated from high-temperature aerosol reactors, and (2) analyzing the physical and chemical pathways of aerosol formation during combustion. Part. 1. Particle size distributions reveal important information about particle formation dynamics. DMAs are widely utilized to measure particle size distributions. However, our knowledge of the initial stages of particle formation is incomplete, due to the Brownian broadening effects in conventional DMAs. The first part of this presentation discusses the applicability of high-resolution DMAs in characterizing sub 2 nm particles generated from high-temperature aerosol reactors, including a flame aerosol reactor (FLAR) and a furnace aerosol reactor (FUAR). Comparison against a conventional DMA (Nano DMA, Model 3085, TSI Inc.) demonstrated that the increased sheath flow rates and shortened residence time indeed greatly suppressed the diffusion broadening effect in a high-resolution DMA (half mini type). The incipient particle size distributions were discrete, suggesting the formation of stable clusters that may be intermediate phases betw
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Physics Colloquium
"Snapping pictures of the proton with heavy ions"
Presented by Bjoern Schenke, BNL
Tuesday, March 7, 2017, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Robert Pisarski
I will present an overview of recent theoretical developments related to the science program at the Relativistic Heavy Ion Collider at Brookhaven National Laboratory and the Large Hadron Collider at CERN. Beginning from heavy ion collisions and the creation of the quark gluon plasma, the most perfect and hottest fluid every created on earth, I will proceed to discuss smaller collision systems, like proton+lead collisions. The experimental data from these show strikingly similar features to heavy ion collisions and I will discuss their possible origins. If the physics in these small systems is also dominated by the fluid dynamic behavior of the created matter, experimental measurements combined with theoretical models give us unprecedented access to the fluctuating shape of the proton.
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NSLS-II Engineering Seminar Series
"High-Resolution Monochromator Development for Nuclear Resonant Scattering"
Presented by Thomas Toellner, X-Ray Science Division,
Tuesday, March 7, 2017, 2 pm
John Dunn Seminar Room, Bldg. 463Hosted by: Sushil Sharma and Mary Carlucci-Dayton
High-resolution monochromators (HRMs) are key components at nuclear resonant scattering beamlines, and their development at the APS has been ongoing for decades. They are used to resolve the frequency spectrum of isotope-specific atomic dynamics using nuclear resonant vibrational spectroscopy and to reduce the enormous electronic charge scattering that accompanies nuclear excitation using synchrotron radiation. The latter allowing the measurement of hyperfine fields using synchrotron Moessbauer spectroscopy. The narrow line-widths (neV) associated with nuclear resonances also offer an excellent diagnostic tool for the characterization of HRMs, and have greatly facilitated their development. HRMs with ultra-high energy-resolution exposed the need for greater energy-alignment stability and prompted the development of cryo-stabilization. A recent prototype sub-meV-bandwidth monochromator for hard X-rays that implements cryo-stabilization has been built that displays a 100-fold improvement in energy-alignment stability over other designs. This unprecedented level of control allows one to observe the intrinsic factors that limit the energy resolution obtainable with silicon. I will present the principle design aspects of this prototype along with its performance, and discuss what has been learned.
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Nuclear Physics Seminar
"Collectivity in small collision systems, what is it?"
Presented by Jiangyong Jia, BNL and Stony Brook University
Tuesday, March 7, 2017, 11 am
Small Seminar Room, Bldg. 510Hosted by: Jin Huang
In recent years, there been rapid progresses in our understanding of the long-range ridge in small collision system at RHIC and LHC. I will discuss the nature of collectivity (flow) driving the ridge, as well as the dominating non-collective (or non-flow) background that complicates the extraction of the ridge. I shows that the standard multi-particle cumulant method, often used to defined collectivity in heavy ion collisions, is overwhelmed by non-collective background in pp and low multiplicity pPb collisions. This problem is resolved with an alternative method based on two or more subevents separated in pseudorapidity (η), and therefore offers a robust data-driven definition of collectivity based on the existence of long-range azimuthal correlations between multiple distinct η ranges. With this new cumulant method, we are able to probe reliably the event-by-event fluctuation of collectivity in small collision systems.
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NSLS-II Friday Lunchtime Seminar Series
"Elemental Concentration and Size Apportionment of Combustion Particles from Wood-fired Appliances" and "Creating Methods for Material Design and Synthesis for Microporous and Mesoporous Materials"
Presented by Monica Gray-Georges and Nicholas Brunelli, Lincoln University of Pennsylvania and Ohio State University
Friday, March 3, 2017, 12 pm
NSLS-II Bldg 743 (LOB 3), room 156Hosted by: Ben Ocko and Shirish Chodankar
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RIKEN Lunch Seminar
"Generalized Nambu-Goldstone theorem"
Presented by Yoshimasa Hidaka, RIKEN
Thursday, March 2, 2017, 12:30 pm
Building 510, Room 2-160Hosted by: Hiromichi Nishimura
Symmetry and its spontaneous breaking are of basic importance for understanding the low energy physics in many-body systems. When a continuum symmetry is spontaneously broken, there exist a zero mode called Nambu-Goldstone (NG) mode, which is well developed in Lorentz invariant systems. In contrast, in non-Lorentz invariant systems, the NG theorem has not been well developed. In this talk, we discuss the recent progress in generalization of NG theorem in non-relativistic systems, open systems, and systems with higher form symmetries.
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RIKEN Lunch Seminar
"The Kibble-Zurek scaling for the Entanglement Entropy on the scalar field in 1+1 dimension"
Presented by Akio Tomiya, CCNU
Monday, February 27, 2017, 12:30 pm
Building 510, Room 2-160Hosted by: Hiromichi Nishimura
The entanglement entropy is a candidate of an entropy in Non-equilibrium physics and recently, relaxation or thermalization is studied through the entanglement entropy with quamtum quenching, which is sudden change of parameter(s) in the Hamiltonian of the system. Global quantum quench with a finite rate which crosses critical points is known to lead to universal scaling of correlation functions as functions of the quench rate. We explore scaling properties of the entanglement entropy of a subsystem of a scaler field on the lattice, harmonic chain, during a mass quench which asymptotes to finite constant values at early and late times and for which the dynamics is exactly solvable. Both for fast and slow quenches we find that the entanglement entropy has a constant term plus a term proportional to the subsystem size. For slow quenches, the constant piece is consistent with Kibble- Zurek predictions. Furthermore, the quench rate dependence of the extensive piece enters solely through the instantaneous correlation length at the Kibble-Zurek time, suggesting a new scaling hypothesis similar to that for correlation functions. This talk is based on arXiv:1702.04359.
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Nuclear Theory Seminar
"A Complete Diagrammatic Implementation of the Kinoshita-Lee-Nauenberg Theorem at Next-to-Leading Order"
Presented by Will Horowitz, University of Cape Town
Friday, February 24, 2017, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Heikki Mantysaari
We show for the first time in over 50 years how to correctly apply the Kinoshita-Lee-Nauenberg theorem diagrammatically in a next-to-leading order scattering process. We improve on previous works by including all initial and final state soft radiative processes, including absorption and an infinite sum of partially disconnected amplitudes. Crucially, we exploit the Monotone Convergence Theorem to prove that our delicate rearrangement of this formally divergent series is correct. This rearrangement yields a factorization of the infinite contribution from the initial state soft photons that then cancels in the physically observable cross section. We derive the first complete next-to-leading order, high-energy Rutherford elastic scattering cross section in the MSbar renormalization scheme as an explicit example of our procedure.
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RIKEN Lunch Seminar
"Path-integral formula for local thermal equilibrium"
Presented by Masaru Hongo, RIKEN
Thursday, February 23, 2017, 12:30 pm
Building 510, Room 2-160Hosted by: Hiromichi Nishimura
Relativistic hydrodynamics is formulated based on the assumption that systems are almost in local thermal equilibrium. However, a quantum field theoretical way to handle such a locally thermalized system has not been clearly clarified. In this study, we develop a complete path-integral formulation of relativistic quantum fields in local thermal equilibrium, which brings about the emergence of thermally induced curved spacetime. The obtained path-integral formula for local thermal equilibrium enables us to derive nondissipative part of hydrodynamic constitutive relations based on symmetry arguments. As one application, we discuss a field theoretical derivation of anomalous hydrodynamics which captures the chiral magnetic/vortical effects.
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RIKEN Lunch Seminar
"The search for gluon saturation in pA collisions and at the EIC"
Presented by Bowen Xiao, Central China Normal University
Thursday, February 16, 2017, 12:30 pm
Building 510, Room 2-160Hosted by: Heikki Mantysaari
In this talk, I plan to discuss the recent theoretical progress towards the exploration of the gluon saturation phenomenon in pA collisions and at the future EIC. Two important pillars of this exploration are the single inclusive forward hadron productions and forward dijet correlations, which have both been computed up to one-loop order within the small-x factorization formalism. Complementary measurements in pA collisions and at the EIC can help us measure small-x gluon distributions and test the generalized small-x factorization. In addition, DIS diffractive dijet process is another interesting process which is sensitive to the dipole Wigner gluon distributions. This process can provide us 3D tomographic images of low-x gluons inside high energy protons and nuclei.
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Physics Colloquium
"Thermalization and hydrodynamization in heavy-ion collisions at high energies"
Presented by Aleksi Kurkela, CERN and Univ. of Stavenger
Tuesday, February 14, 2017, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Robert Pisarski
Describing heavy-ion collisions as hydrodynamical explosions of liquid of quarks and gluons has been a tremendous phenomenological success. A major uncertainty in such modeling arises from what happens during the first 1fm/c of the evolution during which the system is far from local thermal equilibrium. I will describe how the postcollision debris start behaving hydrodynamically, and how the phenomenological modeling of the prehydrodynamical evolution can be improved.
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Condensed-Matter Physics & Materials Science Seminar
"Thermalization and chaos in quantum systems"
Presented by Sriram Ganeshan, Stony Brook University
Tuesday, February 14, 2017, 1:30 pm
Bldg. 734, ISB Conference Room 201 (upstairs)Hosted by: Robert Konik
Thermalization, a common phenomenon in various physical settings, can naturally fail in certain isolated disordered quantum systems, challenging basic tenets of quantum statistical mechanics. Many body localization (MBL) is a canonical example of such an intriguing scenario and, therefore, attracted tremendous attention from condensed matter, statistical physics, and atomic physics communities. Considerable effort has recently gone into establishing the existence of the MBL phase, and the nature of dynamical phase transition from MBL to the thermal phase. However, understanding instabilities to the MBL phase that may lead to the complete or partial restoration of thermalization is still an open question. In this talk, I would focus on two such instabilities to the MBL phase coming from single particle mobility edge and the presence of extensive degeneracy in the many body spectrum. The goal is to identify the most robust form of MBL (in the presence of instabilities) to gain insight into the mechanisms of quantum thermalization.
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Environmental & Climate Sciences Department Seminar
"The Impact of Organic Aerosol Volatility on Aerosol Microphysics for Global Climate Modeling Applications"
Presented by Yuchao 'Chloe' Gao, NASA Goddard Institute for Space Studies, China
Thursday, February 9, 2017, 11 am
Conference Room Bldg 815EHosted by: Robert McGraw
A newly developed box model, MATRIX-VBS [Gao et al., 2017], includes the volatility-basis set (VBS) framework in an aerosol microphysical scheme MATRIX (Multiconfiguration Aerosol TRacker of mIXing state) [Bauer et al., 2008], which is a module within GISS ModelE that resolves aerosol mass and number concentrations and aerosol mixing state. By including the gas-particle partitioning and chemical aging of semi-volatile organic aerosol in MATRIX, we were able to examine its effects on the growth, composition and mixing state of particles. MATRIX-VBS is unique and advances the representation of organic aerosols in Earth system models by greatly improving the traditional and very simplistic treatment of organic aerosols as non-volatile and with a fixed size distribution. Idealized cases representing Beijing, Mexico City, a Finnish and a Southeast U.S. forest were simulated, and we investigated the evolution of mass concentrations and volatility distributions for organic species across the gas and particle phases, as well as their mixing state among aerosol populations. To test and simplify the model, a Monte-Carlo analysis is performed to pin point which processes affect organics the most under varied chemical and meteorological conditions. Since the model's parameterizations have the ability to capture a very wide range of conditions, all possible scenarios on Earth across the whole parameter space, including temperature, humidity, location, emissions and oxidant levels, are examined. These simulations provide information on which parameters play a critical role in the aerosol distribution and evolution in the atmosphere and which do not, and that will facilitate the simplification of the box model, an important step in its implementation in the global model GISS ModelE as a module.
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Particle Physics Seminar
"Di-Higgs at the LHC: Current Status and Future Prospects"
Presented by John Alison, University of Chicago
Thursday, February 2, 2017, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Michael Begel
I will discuss motivations for searching for di-Higgs production at the LHC. Recent results and projected sensitivities will be presented with particular emphasis on the dominant hh->4b channel
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Nuclear Theory/RIKEN Seminar
"What shines brighter, Glasma or Quark-Gluon Plasma?"
Presented by Naoto Tanji, University of Heidelberg
Friday, January 27, 2017, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Heikki Mantysaari
Recent classical-statistical numerical simulations have established the "bottom-up" thermalization scenario of Baier et al. as the correct weak coupling effective theory for thermalization in ultrarelativistic heavy-ion collisions. I will talk on a parametric study of photon production in the various stages of this bottom-up framework to ascertain the relative contribution of the off-equilibrium "Glasma" relative to that of a thermalized Quark-Gluon Plasma. Taking into account the constraints imposed by the measured charged hadron multiplicities at RHIC and the LHC, we find that Glasma contributions are important especially for large values of the saturation scale at both energies. Furthermore, I will report on first kinetic simulations of photon production in the expanding Glasma that will quantify our estimates.