Physics Events
-
MAY
23
Tuesday
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
11 am, Small Seminar Room, Bldg. 510
Tuesday, May 23, 2017, 11:00 am
Hosted 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.
-
MAY
25
Thursday
RIKEN Lunch Seminar
"Mixed Anomaly and Global Consistency"
Presented by Yuya Tanizaki, RBRC
12:30 pm, Building 510, Room 2-160
Thursday, May 25, 2017, 12:30 pm
Hosted 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.
-
MAY
25
Thursday
Particle Physics Seminar
"Higgs boson properties: what we learn from run II of LHC"
Presented by Andrei Gritsan, Johns Hopkins University
3 pm, Small Seminar Room, Bldg. 510
Thursday, May 25, 2017, 3:00 pm
Hosted 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.
-
JUN
15
Thursday
Particle Physics Seminar
"First Results from XENON1T"
Presented by Dr. Fei Gao, Columbia University
3 pm, Small Seminar Room, Bldg. 510
Thursday, June 15, 2017, 3:00 pm
Hosted 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.
-
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.
-
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.
-
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
-
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'
-
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.
-
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.
-
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.
-
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.
-
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."
-
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.
-
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).
-
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.
-
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.
-
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.
-
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.
-
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.
-
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
-
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)
-
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.
-
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.
-
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.
-
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.
-
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.
-
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.
-
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
-
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.
-
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.
-
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.
-
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.
-
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
-
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.
-
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.
-
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.
-
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.
-
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.
-
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.
-
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).
-
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)
-
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.
-
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.
-
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)
-
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.
-
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.
-
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.
-
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
-
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.
-
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.
-
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.
-
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.
-
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.
-
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
-
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.
-
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.
-
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.
-
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''
-
Condensed-Matter Physics & Materials Science Seminar
"Ab Initio electronic structure of solids: correlation effects beyond the GW method"
Presented by Andrei Kutepov, Rutgers University
Thursday, March 2, 2017, 1:30 pm
Bldg. 734, ISB Conference Room 201 (upstairs)Hosted by: ''''Gabi Kotliar''''
TBA
-
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.
-
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.
-
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.
-
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.
-
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.
-
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.
-
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.
-
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.
-
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
-
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.
-
Particle Physics Seminar
"New Models of Baryogenesis"
Presented by Dr. David McKeen, University of Pittsburgh
Thursday, January 26, 2017, 3 pm
Small Seminar Room, Bldg. 510Hosted by: ''Hooman Davoudiasl''
I will describe a new mechanism for creating the matter-antimatter asymmetry of the Universe at low temperatures, i.e. below the QCD confinement temperature, involving the CP-violating oscillation of fermions made of strongly interacting particles. I will also make connections to neutron-antineutron oscillations, clearing up issues that exist in the literature. Novel experimental tests will be discussed.
-
Condensed-Matter Physics & Materials Science Seminar
"Anion-based approaches to engineering functionality in perovskite oxide heterostructures"
Presented by Steve May, Drexel University
Thursday, January 26, 2017, 1:30 pm
ISB Bldg. 734, Conf. Room 201 (upstairs)Hosted by: ''Mark Dean''
Scientific interest in ABO3 perovskite oxides remains intense due to the wide range of physical behavior present in these materials. The ability to control the position, occupation, and composition of the anion site has recently emerged as a new route to tune properties in epitaxial perovskites. This talk will focus on recent and ongoing efforts aimed at developing anion-based approaches to tailor electronic, optical and magnetic properties in oxide heterostructures. First, I will discuss how the position of the oxygen anions can be controlled to stabilize non-bulk-like bond angles and lengths, thereby modifying electronic and magnetic behavior in manganite films and superlattices. In the second half of the talk, I will describe efforts focused on controlling the occupation and composition of the anion site, including reversible oxidation/reduction in thin La1/3Sr2/3FeO3-? films and topotactic fluorination reactions to realize oxyfluoride films
-
RIKEN Lunch Seminar
"From small to moderate-x: beyond the eikonal approximation"
Presented by Andrey Tarasov, BNL
Thursday, January 26, 2017, 12:30 pm
Building 510, Room 1-224Hosted by: '''Hiromichi Nishimura'''
In recent years significant progress has been made in our understanding of the small-x physics beyond the eikonal approximation. Rigorous analysis of the dependence on the transverse momentum helps us better understand not only physics of the Regge limit, but to connect it to the kinematic limit of the moderate-x as well. I'll describe the technique we used in calculation of TMD evolution observed in the Drell-Yan process and present some recent results.
-
C-AD Accelerator Physics Seminar
"Engineering Studies Related to Nuclear Molecular Imaging"
Presented by Dr. Dohyun Kim, Weill Cornell Medicine
Tuesday, January 24, 2017, 4 pm
Bldg 911B, Large Conf. Rm., Rm. A202One of the major uses of radioisotopes is for nuclear molecular imaging using a variety of radiotracers. It is a multidisciplinary science that includes physics, chemistry, biology, computer science, mathematics and medicine with the goal of improving human life. These radiotracers can be used in a PET scanner (or other types of scanners) to generate a three dimensional image of the inside of the human body. PET scanners are used mainly for brain research and cancer detection. The goal of positron emission tomography (PET) is to generate in-vivo images from patients with a disease or abnormal condition. PET scanners detect the 511 keV annihilation gamma rays that are produced when a positron from a nuclear decay interacts with an electron. The gamma rays are given off at nearly 180° from each other and can be detected as originating along a straight line if they arrive at the detectors within a given time interval known as the coincidence window. I will describe the development of a very novel PET scanner with very high resolution using CZT solid state detectors. A novel feature of this system design is that the CZT detectors are rotated 90 degrees from their conventional orientation to use the C/A ratio such that the depth direction is oriented tangentially to the circular FOV of the tomograph. Thus the expected ~0.25 ? depth resolution of the detectors can be used to provide ultra-high resolution in the transaxial plane. The CdZnTe detector PET scanner we developed has a 600 micron FWHM image resolution and an excellent energy resolution of < 2 % FWHM. I will also discuss the development and fabrication of gas phase 11CO2 to 11CO, H11CN, 11CH3I and 11CH3OTf auto synthesis system. These systems are used to generate the radiotracers used with PET. The design and fabrication involve understanding the chemistry, utilizing the physics of flow and transport and engineering a final solution that incorporates these effects.
-
Condensed-Matter Physics & Materials Science Seminar
"Creation and Control of Low Dimensional Electron System in Transition Metal Oxides"
Presented by Milan Radovic, Paul Scherer Institut, Switzerland
Monday, January 23, 2017, 11 am
Building 734, conference room 201Hosted by: '''Cedomir Petrovic'''
Transition Metal Oxides (TMOs) exhibit unique and multifunctional electronic properties (such as high-temperature superconductivity, colossal magnetoresistance, metal-insulator transitions, etc.) directly related to the spin and orbital degrees of freedom of the transition metal d-states. Furthermore, their iso-structural nature permits realization of heterostructures where novel unexpected electronic properties take place. Engineering transition metal oxide surfaces and interfaces carries the potential for achieving new physical properties that radically differ from those of the constituent bulk materials. This is the case of oxide-lowDEGs, which recently showed extraordinary occurrences, including interfacial superconductivity, magnetism, large tuneable spin-orbit coupling and indications of topological states. In my talk, I will present recent spin resolved Angle Resolved Photoemission Spectroscopy (ARPES) measurements of the low dimensional electron gas at SrTiO3 [1, 2, 3], TiO2-anatase and Sr1-xBaxTiO3 showing that these materials have capability for the realization of TMO based electronic device. References: [1] N. C. Plumb, M. Salluzzo, E. Razzoli, M. Månsson, M. Falub, J. Krempasky, C. E. Matt, J. Chang, J. Minár, J. Braun, H. Ebert, B. Delley, K.-J. Zhou, C. Monney, T. Schmitt, M. Shi, J. Mesot1, C. Quitmann, L. Patthey, M. Radovic, Phys. Rev. Lett. 113, 086801 (2014). [2] A. F. Santander-Syro, F. Fortuna, C. Bareille, T. C. Rodel, G. Landolt, N. C. Plumb, J. H. Dil, and M. Radovic, Nature Materials, 13, 1085–1090 doi:10.1038/nmat4107 (2014). [3] Z. Wang, S. McKeown Walker, A. Tamai, Z. Ristic, F.Y. Bruno, A. de la Torre, S. Ricco, N.C. Plumb, M. Shi, P. Hlawenka, J. Sanchez-Barriga, A. Varykhalov, T.K. Kim, M. Hoesch, P.D.C. King, W. Meevasana, U. Diebold, J. Mesot, M. Radovic, and F. Baumberger, Nature Materials 15, 835–839 (2016) doi:10.1038/nmat4623 (2016).
-
Nuclear Theory Seminar
"Helicity Evolution at Small x and the Proton Spin"
Presented by Yuri Kovchegov, Ohio State University
Friday, January 20, 2017, 2 pm
Small Seminar Room, Bldg. 510Hosted by: ''Heikki Mantysaari''
We construct small-x evolution equations which can be used to calculate quark and anti-quark helicity TMDs and PDFs, along with the g_1 structure function. These evolution equations resum powers of alpha_s ln^2 (1/x) in the polarization-dependent evolution along with the powers of alpha_s ln (1/x) in the unpolarized evolution which includes saturation effects. The equations are written in an operator form in terms of polarization-dependent Wilson line-like operators. While the equations do not close in general, they become closed and self-contained systems of non-linear equations in the large-N_c and large-N_c & N_f limits. After solving the large-N_c equations numerically we obtain the following small-x asymptotics for the flavor-singlet g_1 structure function along with quarks helicity PDFs and TMDs (in absence of saturation effects): g_1^S (x, Q^2) ~ \Delta q^S (x, Q^2) ~ g_{1L}^S (x, k_T^2) ~ ( 1/x )^{alpha_h} \approx t( 1/x )^{2.31 \sqrt{\alpha_s N_c/(2pi}} This result is valid for all flavors. We also give an estimate of how much of the proton's spin may reside at small x and what impact this has on the so-called ``spin crisis.'' This work would help one better understand longitudinal polarization data to be obtained at the proposed Electron-Ion Collider (EIC).
-
Center for Functional Nanomaterials Seminar
"Amyloid Self-Assembly and Sequence-Dependent Interactions with Plasmonic Nanoparticles"
Presented by Shih-Ting (Christine) Wang, Imperial College London, United Kingdom
Thursday, January 19, 2017, 2 pm
CFN, Bldg 735, Conference Room A, 1st FloorHosted by: ''Oleg Gang''
Nanoparticles (NPs) have been used to inhibit or modulate the peptide fibrillation as a potential therapeutic strategy and to understand the molecular mechanisms of amyloid diseases. Particularly, gold nanoparticles (AuNPs) have been widely used to study peptide/inorganic NP interactions due to the tunable size, surface and plamonic properties. In this talk, I will present the study of interaction of AuNPs with islet amyloid polypeptide (IAPP), which features in type 2 diabetes pathogenesis by self-assembly into fibrils and peptide-induced disruption of cell membranes. Amyloid fibrils share a distinct β-sheet structure, with the structural diversity controlled by the amino acid sequence. To elucidate the key mechanisms of amyloid self-assembly and provide unique viewpoints on the interactions with NPs, polymorphic fibril structures will firstly be discussed using amyloidogenic peptides that are designed based on the IAPP sequence. The observed amyloid fibrillation and hydrogelation controlled by the peptide structure also led to a proposed relationship between amyloid structure and self-assembly behaviour. Next, I will present the systematic study of IAPP/AuNP interactions, in which the strong binding is initiated by the metal-binding sequence in the hydrophilic peptide domain. Structural transition accelerated in a NP size-dependent manner also implies a facet-dependent IAPP/AuNP interaction. Based on these findings, liquid cell transmission electron microscopy was used for direct visualisation of the dynamic growth of AuNPs in presence of IAPP fibrils. The results show growth of branch(star)-shaped AuNPs in the presence of IAPP fibrils, suggesting a preferred nucleation site for Au binding and subsequent growth on the amyloid template.
-
RIKEN Lunch Seminar
"Vector mesons and chiral symmetry restoration"
Presented by Fabian Rennecke, Heidelberg University
Thursday, January 19, 2017, 12:30 pm
Building 510, Room 2-160Hosted by: 'Hiromichi Nishimura'
Vector mesons play a prominent role for the detection of chiral symmetry restoration in the quark-gluon plasma since their in-medium modifications are directly observable in dilepton spectra. However, a direct connection between their in-medium modifications and chiral symmetry restoration remains elusive. To shed some light on this, I will first address the question how chiral symmetry breaking and the light (vector) mesons emerge from the underlying quark-gluon dynamics. Then, I will present preliminary results on the in-medium spectral functions of the rho and a1 mesons obtained from analytic continuation of Euclidean two-point functions.
-
Particle Physics Seminar
"Ultra-Fast Silicon Detector for precise timing at CMS"
Presented by Nicolo' Cartiglia, Torino
Thursday, January 19, 2017, 11 am
Small Seminar Room, Bldg. 510Hosted by: 'Alessandro Tricoli'
In this seminar I will first review the physics case for a hermetic timing detector for charge particles to be installed in CMS in the years 2024-25 in preparation of the High Luminosity upgrade of the LHC accelerator (HL-LHC). Then I will present the possible technologies currently under studies for the timing detector and then I will concentrate on explaining the basics principles of Ultra-fast Silicon Detectors and their performances. I will conclude with a brief outline of the future R&D steps for the construction of the timing detector.
-
Particle Physics Seminar - SB/BNL Joint Cosmo Seminar
"Hunting down systematics in modern galaxy surveys"
Presented by Mohammadjavad Vakili, NYU
Wednesday, January 18, 2017, 1:30 pm
Stony Brook UniversityWith the next generation of wide field galaxy surveys, both spectroscopic and photometric, we expect to achieve unprecedented constraints on the expansion history of the universe and the growth of structure. Maximizing the flow of information from these rich datasets to constraints on our physical models requires accurate characterization of systematic uncertainties. First, we present a method for estimation of covariance matrices of galaxy clustering measurements with spectroscopic surveys. We show that our method enables us to generate accurate galaxy mocks needed for BAO and RSD analyses on nonlinear scales. Then, we present the main challenges in extracting cosmological information from lensing measurements of deep imaging surveys. We show that employing novel techniques in estimation of the point spread function can keep this major systematic under control. Finally, we discuss various approaches for improvement of the photometric redshifts for the imaging surveys. We demonstrate how the precision and accuracy of photometric redshifts can be greatly enhanced if we take advantage of combining different datasets.
-
Physics Colloquium
"And yet they attract: superconductivity in the presence of strong repulsion"
Presented by Andre-Marie Tremblay, University of Sherbrooke, Quebec, Canada
Tuesday, January 17, 2017, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: ''Wenhu Xu''
Band theory and the BCS theory of superconductivity are two pillars of the quantum theory of solids. High-temperature superconductors belong to a family of materials where both of these, band theory and BCS, fail. Layered organic materials of the BEDT family are another example of materials that are hard to understand within conventional approaches. The root cause of these failures can be traced to strong electronic repulsion. I will start from the simplest model that takes into account the competition between kinetic and potential energy, the Hubbard model. I will show how cluster generalizations of dynamical mean-field theory for this model shed light on these problems. The interaction-induced metal-insulator transition (Mott transition) can serve as an organizing principle for the phase diagrams.
-
Nuclear Theory/RIKEN Seminar
"Going with the flow: solving sign problems in complex space"
Presented by Paulo Bedaque, University of Maryland
Friday, January 13, 2017, 2 pm
Small Seminar Room, Bldg. 510Hosted by: ''Heikki Mantysaari''
We discuss a new approach to solve the sign problem arising in the Monte Carlo evaluation of path integrals. It is based on deforming the contour of integration into complex space. We will argue that for conceptual and numeric reasons it may be advantageous not to use the steepest descent manifolds (thimbles). We will discuss a variety of algorithms and their application to field theories with a fermionic sign problem and to quantum mechanical models, including real time dynamics.
-
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
Friday, January 13, 2017, 1:30 pm
Seminar Room 2nd Floor Bldg 734Hosted 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.
-
Particle Physics Seminar
"The muon g-2 experiment at Fermilab"
Presented by Vladimir Tishchenko, BNL
Friday, January 13, 2017, 10 am
Small Seminar Room, Bldg. 510Hosted by: 'Xin Qian'
There exists a long-standing, intriguing, discrepancy between the BNL E821 measurement and the Standard Model (SM) prediction for the muon anomalous magnetic moment, $a_{\mu} \equiv (g-2)/2$, at the level of about three standard deviations ($3\sigma$). To test this discrepancy, a new muon $(g-2)$ experiment E989 at Fermilab will improve the experimental uncertainty by a factor of four. Providing that the central value remains unchanged, the new measurement would result into more than $5\sigma$ ``discovery-level'' deviation from the SM. The experiment at Fermilab will employ the original BNL storage ring with an intense new muon source and state-of-the-art detector systems. I will review the current status of the design of new components and upgrades that are required to achieve the challenging precision goal of the experiment.
-
Particle Physics Seminar
"Analysis Methods in Neutrino Experiments"
Presented by Dr. Thomas Junk, Fermilab
Thursday, January 12, 2017, 3 pm
Small Seminar Room, Bldg. 510Hosted by: ''Xin Qian''
Current and planned neutrino experiments address fundamental questions in the neutrino, astrophysical, nuclear, and new physics sectors with ambitious, large-scale facilities and detectors. Maximizing the sensitivity and physics reach of these experiments is the guiding principle for the design of the apparatus as well as the analysis techniques applied to infer results from the data. These experiments, however, pose challenges in this process: the data frequently have ambiguities and some quantities are not measurable, such as the momenta of outgoing neutrinos or recoiling nuclei. Detectors with high density and spatial granularity provide a large number of measured values for each event that must be sifted through to obtain even basic reconstructed quantities. The impact of the values of model parameters on the predicted event rates is not linear but is frequently oscillatory. Systematic uncertainties must be highly constrained in order to tease out small effects. To address these challenges, a variety of sophisticated techniques have been adapted from earlier experiments, such as well-established statistical methods and analysis techniques. New, innovative tools developed in other fields, such as deep-learning methods, are being applied to neutrino experiments. I will give a survey of some of the interesting developments being applied and planned for the future.
-
RIKEN Lunch Seminar
"Plasmon mass scale and linearized gauge field fluctuations in classical Yang-Mills theory"
Presented by Jarkko Peuron, University of Jyvaskyla
Thursday, January 12, 2017, 12:30 pm
Building 510, Room 2-160Hosted by: 'Heikki Mantysaari'
In this talk I discuss the determination of plasmon mass in classical real-time Yang-Mills theory on a lattice in 3 spatial dimensions. I compare 3 different methods to determine the plasmon mass : a hard thermal loop expression in terms of the particle distribution, an effective dispersion relation constructed from fields and their time derivatives, and by measuring oscillations between electric and magnetic field modes after artificially introducing a homogeneous color electric field. Due to plasma instabilities, small quantum fluctuations on top of the classical background may significantly affect the dynamics of the system. I argue for the need for a numerical calculation of a system of classical gauge fields and small linearized fluctuations in a way that keeps the separation between the two manifest. I derive and test an explicit algorithm to solve these equations on the lattice, maintaining gauge invariance and Gauss's law.
-
Physics Colloquium
"Searches for Decays of Heavy Higgs Boson to Gauge Bosons with the ATLAS detector"
Presented by Scott Snyder, BNL
Tuesday, January 10, 2017, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: 'Andrei Nomerotski'
Following the discovery of the Higgs boson in 2012, the ATLAS experiment at the LHC has been searching for signs of new physics related to the Higgs boson. One promising area is the seach for new, heavy Higgs-like scalars decaying to a pair of vector gauge bosons. This talk will summarize recent ATLAS searches for a heavy scalar decaying to two Z bosons, using the sqrt(s)=13 TeV data from Run 2
-
Nuclear Physics Seminar
"Phenomenology of Wigner distributions"
Presented by Andrei Belitsky, Arizona State University
Tuesday, January 10, 2017, 11 am
Small Seminar Room, Bldg. 510Hosted by: ''Oleg Eyser''
We overview physics of nucleon phase space distributions and diverse high energy processes where they are accessible with current and future machines.
-
Nuclear Theory/RIKEN Seminar
"Prompt atmospheric neutrino flux and forward charm production in proton-nucleus collisions"
Presented by Anna Stasto, Penn State
Friday, January 6, 2017, 2 pm
Small Seminar Room, Bldg. 510Hosted by: ''Heikki Mantysaari''
The discoveries of the extraterrestrial neutrino flux by IceCube renewed interest in the precise evaluation of the background neutrinos which are produced in the atmosphere due the cosmic ray interactions. One of the most relevant processes at high energies is the charm and beauty production in proton-nucleus collisions which needs to be evaluated at very high energies where small x effects may become important. I will discuss a recent calculation of the forward charm production in pp and pA, and compare results from different models which include small x effects due to resummation and saturation. Comparison with the LHC data will be presented and nuclear effects on light nuclei will also be discussed. Finally, I will show the resulting prompt neutrino flux and its uncertainties and discuss the potential improvements.
-
Center for Functional Nanomaterials Seminar
"DNA Assembled Nanoparticle Clusters for Nanomedicine"
Presented by Liangcan He, University of Colorado Boulder
Monday, December 19, 2016, 1:30 pm
CFN, Bldg 735, Conference Room A, 1st FloorHosted by: ''Oleg Gang''
In this talk, I will describe the use of nucleic acids to assemble different types of nanocrystals for theranostic applications. In the first part, I will talk about our work on coupling gold nanoparticles (AuNPs) and gold nanostars (AuNSs) to silica-coated upconverting nanoparticles (UCNPs) and their effect on photoluminescence. The experimental and simulation studies showed that the orientation and distance of the UCNP with respect to the core and arms of the gold nanostructures played a significant role in photoluminescence. Also, the AuNS-UCNP assemblies were able to cause rapid gains in temperature of the surrounding medium enabling their potential use as a multi-therapy agent. Then, photodynamic therapy (PDT) was induced by embedding singlet oxygen photosensitizers in mesoporous silica shells on the UCNPs. It showed the Au-UCNP clusters with optimized plasmon resonance and compositions could provide both in vitro imaging contrast and combined cell killing through simultaneous photothermal (PTT) and photodynamic (PDT) therapy under NIR light photoexcitation. In addition to the Au-UCNP studies, I will also describe our recent efforts on building well-defined core-satellite porphyrinic metal-organic framework (MOF)-UCNP assemblies by DNA templating. In this work, UCNPs were well organized around a centrally located MOF nanoparticles. Under NIR irradiation, the emitted light from the assembled UCNPs excited each core MOF NP to produce singlet oxygen (1O2) at significantly greater amounts than that produced from simply mixing UCNPs and MOF NPs, demonstrating their promise as theranostic photodynamic agents. In the second part, I will briefly introduce my graduate work in the Ph.D. study on noble metal nanoparticles-MOFs hybrid materials for SERS detecting and multifunctional drug delivery vehicles.
-
Nuclear Theory/RIKEN Seminar
"Proton fluctuations and multi-particle rapidity correlations"
Presented by Kevin Dusling, PRL
Friday, December 16, 2016, 2 pm
Small Seminar Room, Bldg. 510Hosted by: 'Heikki Mantysaari'
The effect of intrinsic fluctuations of the proton saturation momentum scale on event-by-event rapidity distributions in small systems is explored. Saturation scale fluctuations generate an asymmetry in the single particle rapidity distribution in each event resulting in genuine n-particle correlations. We introduce a color domain model that naturally explains the centrality dependence of the two-particle rapidity correlations recently measured by ATLAS, constraining the probability distribution of saturation scale fluctuations in the proton. Predictions for n=4, 6 and 8 particle rapidity correlations find that the four- and eight-particle cumulant change sign at intermediate multiplicities, a signature which could be tested experimentally.
-
Nuclear Physics Seminar
"Evidence for light-by-light scattering in 5.02 TeV Pb+Pb collisions with the ATLAS detector at the LHC"
Presented by Mateusz Dyndal, DESY
Tuesday, December 13, 2016, 11 am
Small Seminar Room, Bldg. 510Hosted by: 'Peter Steinberg'
I report evidence for light-by-light scattering, using 480ub^−1 of 5.02 TeV Pb+Pb collision recorded by the ATLAS experiment at the LHC. After background data at subtraction and analysis corrections, the cross section of gamma gamma-> gamma gamma process for photon transverse momentum, E_T > 3 GeV, photon pseudorapidity, |η| < 2.4, diphoton invariant mass greater than 6 GeV, diphoton transverse momentum lower than 2 GeV and diphoton aco- planarity below 0.01, has been measured to be 70 ± 20 (stat.) ± 17 (syst.) nb, which is in agreement with the SM prediction of 49 ± 10 nb.
-
Nuclear Theory/RIKEN Seminar
"Hydrodynamics, the gradient expansion and transient modes"
Presented by Michal Heller, Perimeter Institute
Friday, December 9, 2016, 2 pm
Small Seminar Room, Bldg. 510Hosted by: ''Heikki Mantysaari''
I will discuss recent developments at the interplay between hydrodynamic gradient expansion and transient modes in expanding plasma.
-
RIKEN Lunch Seminar
"Analytic Results for Color Glass In Space-Time Coordinates"
Presented by Rainer Fries, Texas A&M University
Thursday, December 8, 2016, 12:30 pm
Building 510, Room 2-160Hosted by: ''Heikki Mantysaari''
I will start by reviewing some previous results for the McLerran-Venugopalan model for nuclear collisions solved analytically in space-time coordinates. I will then discuss some recent work on initial angular momentum in the resulting Yang-Mills system, which leads to an interesting picture of gluon flow in the event plane. I will also describe further evolution of these results in fluid dynamics. Time permitting I will touch on ongoing efforts to construct an event generator based on analytic solutions.
-
Joint: YITP/HET
"Enhancing searches for beyond the Standard Model physics at the LHC"
Presented by Michele Papucci, Berkeley
Wednesday, December 7, 2016, 2:30 pm
YITP Seminar RoomIn this talk I'll present recent work on improving the capabilities for looking for new physics at the LHC, both for exotics BSM signals (hidden valleys) and for Dark Matter. I will also discuss soon to be publicly available tools for connecting LHC results with theoretical models.
-
Nuclear Theory/RIKEN Seminar
"Squeeze Out"
Presented by Ron Longacre, BNL
Wednesday, December 7, 2016, 11 am
Small Seminar Room, Bldg. 510Hosted by: '''Heikki Mantysaari'''
Squeeze out happen when the expanding central fireball flows around a large surface flux tube in a central Au-Au collision at RHIC. We model such an effect in a flux tube model. Two particle correlations with respect to the $v_2$ axis formed by the soft fireball particles flowing around this large flux tube is a way of measuring the effect.
-
Nuclear Physics Seminar
"Quarkonium and Open Heavy Flavor productions at collider energies in Small-x formalism"
Presented by Kazuhiro Watanabe, Old Dominion University/Jefferson Lab
Tuesday, December 6, 2016, 11 am
Small Seminar Room, Bldg. 510Hosted by: 'Oleg Eyser'
Heavy quark pair production in high energy proton-nucleus (pA) collisions provides valuable information on the gluon saturation dynamics at small-x of a heavy nucleus. Nowadays, large amounts of data of quarkonium, open heavy flavor, and decay lepton accumulated by RHIC and LHC enable us to examine the calculations in Small-x formalism or Color Glass Condensate (CGC). Essentially, the calculations of heavy quark pair production have been based on the Small-x/CGC framework at leading order (LO) with the running coupling Balitsky-Kovchegov equation (rcBK) which includes a subset of next-to-leading order (NLO) correction. A main difference between pp and pA collisions is the choice of the initial saturation scale in the rcBK equation. The recent theoretical computations have gradually clarified the gluon saturation effect in pA collision by comparing with data on the transverse momentum spectrums and the nuclear modification factors measured at RHIC and LHC. In this talk, we will review the recent studies of heavy quark pair production in the Small-x/CGC framework and discuss the relevant topical issues. Furthermore, we will discuss the Sudakov implementation in Small-x formalism which has received attention in recent years. I will show that the Sudakov effect on top of the saturation effect is indeed indispensable for Upsilon production.
-
Nuclear Theory/RIKEN Seminar
"Renormalization-group flow of the effective action of cosmological large-scale structures"
Presented by Stefan Flörchinger, Heidelberg
Friday, December 2, 2016, 2 pm
Small Seminar Room, Bldg. 510Hosted by: '''Heikki Mantysaari'''
The large scale structure of the universe forms a particular type of fluid which is governed by the properties of dark matter. I discuss how one can derive renormalization group equations for the effective action that describes the statistical properties of this fluid. Taking into account in particular effective viscosity and sound velocity terms leads to an improved framework to determine density and velocity power spectra.
-
CFN Colloquium
"The emergence of hybrid-perovskites for low-cost, high-efficiency optoelectric devices"
Presented by Aditya D. Mohite, Los Alamos National Laboratory
Thursday, December 1, 2016, 4 pm
CFN, Bldg 735, Seminar Room, 2nd FloorHosted by: ''''Matthew Sfeir''''
Hybrid (inorganic--organic) perovskites have demonstrated an extraordinary potential for clean sustainable energy technologies and low--cost optoelectronic devices such as solar cells; light emitting diodes, detectors, sensors, ionic conductors etc. In spite of the unprecedented progress in the past six years, one of the key challenges that exist in the field today is the large degree of processing dependent variability in the structural and physical properties. This has limited the access to the intrinsic properties of hybrid perovskites and led to to multiple interpretations of experimental data. In addition to this, the stability and reliability of devices has also been strongly affected and remains an open question, which might determine the fate of this remarkable material despite excellent properties. In this talk, I will describe our recently discovered approach for thin--film crystal growth as a general strategy for growing highly crystalline, bulk--like thin--films of both three--dimensional (3D) and layered two--dimensional (2D) hybrid perovskites that overcomes the above issues by allowing access to the intrinsic charge and energy transport processes within the perovskite thin--films and results in reproducible and stable high performance optoelectronic devices.
-
Condensed-Matter Physics & Materials Science Seminar
"Complexity in Spin-Frustrated Rock-Salt Manganites"
Presented by Alexandros Lappas, Institute of Electronic Structure and Laser, Foundation for Research & Technology, Greece
Thursday, December 1, 2016, 1:30 pm
ISB Bldg. 734, Conf. Rm. 201 (upstairs)Hosted by: 'Emil Bozin'
Complexity in transition metal oxides is the outcome of simultaneously active electron degrees of freedom (spin-charge-orbital) and their evolution under the restrictions imposed by the geometry of the underlined crystal lattice. Consequently, the materials' response to competing states requires that we assess structural correlations across a wide range of length and time scales. Taking advantage of cutting-edge structural facilities accessed at neutron [1, 2], synchrotron X-ray [3] and electron microscopy [4] labs we address current limitations in understanding the crystallographic structure of layered rock-salt type triangular-lattice manganites of the AMnO2 type (A= Na, Cu). The unexpected coexistence of long- and short-range magnetic correlations [3, 5] due to two major opposing effects (elastic vs. magnetic exchange) of similar magnitude, lead to nearly equivalent, competing structural phases enabling infinitesimal quenched disorder to locally lift the differing degree of inherent frustration in the parent AMnO2 phase. These manganites provide a paradigm of a rarely observed nanoscale inhomogeneity in an insulating spin system, an intriguing complexity of competition due to geometrical frustration. The dramatic impact of topology and site-disorder on frustrated magnetism is further demonstrated by the hydrated variant of the NaMnO2 antiferromagnet, which gives way to a strongly interacting spin-glass state, indicative of the subtle balance of competing processes in multivalent two-dimensional systems [6]. [1] M. Giot et al., Phys. Rev. Lett. 2007, 99, 247211. [2] C. Vecchini et al., Phys. Rev. B 2010, 82, 094404. [3] A. Zorko et al., Nat. Commun. 2014, 5, 3222. [4] A.M. Abakumov et al., Chem. Mater. 2014, 26, 3306. [5] A. Zorko et al., Sci. Rep. 2015, 5, 9272. [6] I. Bakaimi et al., Phys. Rev. B 2016, 93, 184422.
-
HET/RIKEN Seminars
"Heavy meson decays to light resonances"
Presented by Luka Leskovec, University of Arizona
Wednesday, November 30, 2016, 2 pm
Small Seminar Room, Bldg. 510Hosted by: ''Mattia Bruno''
Lattice QCD calculations of electroweak decays with single, strong-interaction-stable hadrons in the initial and final state have recently reached a high level of precision. Many phenomenologically important decays, however, involve hadronic resonances, and their naive analysis on the lattice leads to uncontrolled systematic errors. Recent theoretical developments in the finite-volume treatment of $1 \to 2$ transition matrix elements now enable us to perform rigorous lattice calculations of electroweak decays to light resonances such as the $\rho$. After presenting the Briceno-Hansen-Walker-Loud formalism, I will discuss our numerical implementation for the $D\to\rho \ell \nu$ and $B\to\rho \ell \nu$ decays, where we aim to quantify the effect of the unstable nature of the $\rho$. Our calculations are performed on a gauge ensemble with 2+1 flavors of clover fermions with a pion mass of ~320 MeV and a lattice size of ~3.6 fm.
-
Physics Colloquium
"Isolated quantum systems in extreme conditions: From heavy-ion collisions to ultracold quantum gases"
Presented by Juergen Berges, University of Heidelberg
Tuesday, November 29, 2016, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: ''Rob Pisarski''
Isolated quantum systems in extreme conditions can exhibit characteristic common properties despite dramatic differences in key parameters such as temperature, density, field strength and others. The existence of universal regimes, where even quantitative agreements between seemingly disparate physical systems can be observed, drives a remarkable convergence of research activities across traditional lines of specialization. I will describe the concerted research efforts by the recently established Heidelberg Collaborative Research Center ISOQUANT in collaboration with BNL and discuss recent developments concerning the thermalization dynamics of non-Abelian plasmas and ultracold atoms.
-
Nuclear Physics Seminar
"Accessing Gluon Polarization with Di-jets: Present and Future"
Presented by Brian Page, BNL
Tuesday, November 29, 2016, 11 am
Small Seminar Room, Bldg. 510Hosted by: 'Oleg Eyser'
Despite extensive theoretical and experimental effort, a detailed understanding of how the proton spin is built up from the spins and orbital angular momenta of its constituents remains elusive. Polarized fixed-target deep inelastic scattering data has constrained the contribution from quark and anti-quark helicities to be roughly 30% for parton momentum fractions greater than 10^-3, while inclusive jet and $\pi^0$ asymmetry results from the STAR and PHENIX experiments at RHIC have placed strong constraints on the gluon helicity contribution for momentum fractions greater than 0.05. This talk will detail the extension of STAR inclusive jet measurements to correlated di-jet measurements, which better constrain the initial partonic kinematics. Recently released di-jet asymmetry results from STAR will be presented and the status of future measurements will be discussed. Di-jet asymmetry measurements will also play an important role in constraining the gluon helicity contribution to the proton spin at a future Electron-Ion Collider, and the prospects for such measurements will be outlined.
-
Condensed-Matter Physics & Materials Science Seminar
"X-ray Photon Correlation Spectroscopy at Large Angles"
Presented by Mark Sutton, McGill University
Tuesday, November 22, 2016, 1:30 pm
ISB Bldg. 734, Conf. Room 201 (upstairs)Hosted by: 'Mark Dean'
Xray photon correlation spectroscopy (XPCS) has proven to be a powerful way to study time correlations in equilibrium systems. The straight forward extension to two-time correlations has also proven very useful. To date, most XPCS work has been done using small-angle x-ray scattering (SAXS). As with conventional x-ray diffraction, the information in disordered Bragg peaks (large angle scattering) often contains more information but it can be harder to interpret. In this talk, I will discuss several results using large angle XPCS which explore some of the complications and the resulting extra information obtained.
-
Condensed-Matter Physics & Materials Science Seminar
"Probing the magnetic structure of EuPtIn4 via x-ray resonant magnetic scattering"
Presented by Jose Renato Mardegan, Deutsche Elektronen-Synchrotron (DESY), Germany
Tuesday, November 22, 2016, 11 am
ISB Bldg. 734, Seminar Rm. 201 (upstairs)Hosted by: ''Ian Robinson''
The search for fascinating materials with interesting electronic and magnetic properties has led to an enormous development in diverse areas of condensed matters physics. In particular, the Indium-rich materials containing rare-earth elements can host exotic physical phenomena emerging from the competition and/or cooperation of several physical mechanisms such as the Ruderman-Kittel-Kasuya-Yosida (RKKY) magnetic interaction, heavy fermion (HF) behavior, crystalline electric field (CEF) and Kondo effects[1,2].Since the magnetic ordering and the screening of f-electrons have an important role in the ground state properties of these materials, the magnetic structure determination can be a powerful tool to understand how the moments of the magnetic ions are interacting among each other. In this sense, x-ray resonant magnetic scattering (XRMS) technique was employed to solve the magnetic structure at low temperature of the new intermetallic EuPtIn4 compound. At the resonant energy of the Eu ion (7617 eV – L2 edge), magnetic incommensurate (ICM) reflections with propagation vector type (1/2, 1/2, τ) with τ ~ 0.427 were observed. Temperature and magnetic field dependence performed at the magnetic reflections reveal an AFM coupling with a Néel temperature TN = 13.1 K and a spin flop transition above 3 T, respectively. In addition, we do not observe any magnetic anomalies related to a second phase transition as suggested in the previously reported macroscopic measurements [3,4]. The ICM phase observed at low temperature is due to geometric frustration of the Eu ions in which the RKKY exchange interaction cannot be simultaneously satisfied. Although the EuPtIn4 compound displays similar properties to a heavy fermion compound such as exotic magnetic structure and enhancement of Sommerfeld coefficient, further investigation must be performed in this new series of materials.[1] Z. Fisk, et al., Proc. Natl. Acad. Sci. USA 92, 6663 (1995).[2] P. Coleman, Handb
-
Nuclear Physics Seminar
"Chromodynamic Rutherford Scattering?"
Presented by John Dainton, Cockcroft Insitute, University of Liverpool
Tuesday, November 22, 2016, 11 am
Small Seminar Room, Bldg. 510Hosted by: ''Oleg Eyser''
It is asserted that precision measurements of exclusive processes in high-luminosity electron-hadron interactions are the way forward in understanding hadron physics in Nature. Such processes involve the control of more than one scale and thereby enable experimental analysis in terms of phenomenology which can then challenge theoretical calculation in specific ways and on which it will be possible to build a full understanding of chromodynamic mechanism. The presentation is built on initial steps in an on-going analysis of published measurements of exclusive meson production at the HERA ep collider. It already can be seen to indicate that the assertion could well be well justified with precision measurements in the future in a high luminosity electron hadron collider.
-
Particle Physics Seminar
"The Short Baseline Neutrino program: laying the groundwork for DUNE"
Presented by Georgia Karagiorgi, Columbia University
Tuesday, November 22, 2016, 9:30 am
Small Seminar Room, Bldg. 510Hosted by: '''Xin Qian'''
The Short Baseline Neutrino (SBN) Program comprises three liquid argon time projection chamber detectors which are planning to study neutrinos from the Booster Neutrino Beamline at Fermilab, at three different locations close to the neutrino production. The trio of detectors will be able to perform precise neutrino cross section measurements, and search for short-baseline neutrino oscillations and other non-standard effects, addressing pressing questions in the field of neutrino oscillations. The SBN detectors also share the same detector technology as the future, O(100) times larger detector that will be employed for the Deep Underground Neutrino Experiment. They therefore provide a testbed for R&D and for demonstrating the liquid argon TPC technology and its scalability. This seminar will highlight selected physics and R&D opportunities with SBN.
-
Condensed-Matter Physics & Materials Science Seminar
"Tracking chemical reactions with time-resolved x-ray spectroscopic techniques"
Presented by Tadese Abebaw Assefa, European XFEL Laboratory, Germany
Monday, November 21, 2016, 1:30 pm
ISB Bldg. 734, Conf. Rm. 201 (upstairs)Hosted by: ''Ian Robinson''
Transition metal compounds play a significant role in many chemical and biologically relevant processes. Hereby charge transfer, ligand detachment and attachment processes are fundamental ingredients, which often determine the outcome of a given chemical reaction. We investigated aqueous ferrocyanide ([FeII(CN)6]4-) ions, which undergoes charge transfer and ultrafast ligand dissociation upon irradiation of 266 and 355 nm laser light. Time-resolved (TR) x-ray absorption and emission spectroscopies (XAS and XES) deliver information about structural and electronic changes in real-time implemented to follow the chemical reaction. Synchrotron-based studies are limited with 100ps time resolution enables us to disentangle simultaneous photoproducts formed after 266 nm laser excitation. Furthermore, we investigated the ultrafast ligand dissociation of aqueous ferrocyanide ions upon irradiation of 355 nm laser light at the x-ray Free Electron Laser facility (SACLA, Japan). Based on a comparison of the simulated pre-edge peaks of 1s→3d transition with the experimental data, we concluded that the reaction pathway commences via ligand detachment resulting pentacoordinated intermediate complex ([FeII(CN)5]3-), followed by the formation of the long-lived photoaquated complex ([FeII(CN)5(H2O)]3-). The ligand detachment and attachment process takes 12.43 ± 5.77 ps. TR XES results also reveal spin state change in the intermediate state. Combining these findings we interpret the consecutive steps of ligand exchange mechanism for ferrocyanide ions. Also, we characterise the molecular structure of photoexcited [FeII(terpy)2]2+ molecule via TR Extended X-ray absorption fine structure (EXAFS). The data analysis in energy space used two structural model expansions which are the representations of DFT predicted 5E and 5B2 quintet high spin states. After statistical evaluation of the two models, the 5E high spin state model is in better agreement with experimental data. The ener
-
Nuclear Theory/RIKEN Seminar
"Phase structure and dynamics of dense QCD"
Presented by Armen Sedrakian, Frankfurt
Friday, November 18, 2016, 2 pm
Small Seminar Room, Bldg. 510Hosted by: ''''Heikki Mantysaari''''
In the first part of the talk I will discuss recent computations of the transport coefficients of dense QCD from the Kubo formalism on the basis of a two-flavor model of QCD. The second part of the talk will discuss the properties of compact stars featuring color superconducting phases of dense QCD. This will include modeling of massive compact stars, neutrino cooling of such stars, and possible signatures of a phase transition within the QCD phase diagram in the X-ray data from the young neutron star in Cassiopea A.
-
Particle Physics Seminars- SB/BNL Joint Cosmo Seminar
"A more precise and accurate route from sky images to cosmological constraints"
Presented by Gary Bernstein, University of Pennsylvania
Thursday, November 17, 2016, 3 pm
Small Seminar Room, Bldg. 510Hosted by: ''Anze Slosar''
Current (e.g. DES) and future (e.g. LSST, Euclid) experiments aim to convert multiband images of the sky into precise constraints on cosmological models, neutrino masses, and modifications of general relativity. This standard path for this inference involves making point estimates of the galaxies' redshifts (from observed colors) and weak gravitational lensing distortions (from observed morphologies), then combining these into various cross-correlations and other summary statistics that are compared to numerical simulations of the Universe. These estimators require a slew of empirical corrections to various biases, and have yet to demonstrate accuracies sufficient to reduce biases below systematic errors. I describe two steps to greatly simplify this process and eliminate the need for simulation-based calibration of estimators: first, a practical means to estimate the joint posterior probability of a galaxies' redshift and line-of-sight lensing; second, a method to sample from the posterior distribution of all mass distributions and cosmologies conditional on the galaxy density and lensing data. The main advantages of the new scheme include improved lensing and photo-z accuracy (to the required part-per-thousand level), recovery of non-Gaussian information that is lost in the usual 2-point summary statistics, and correct propagation of uncertainties (including photo-z uncertainties) into the cosmological inferences.
-
Nuclear Theory/RIKEN Seminar
"Quantum-field-theoretical approach to shear and bulk relaxation times"
Presented by Alina Czajka, McGill
Thursday, November 17, 2016, 12:30 pm
Building 510, Room 2-160Hosted by: ''Heikki Mantysaari''
The shear and the bulk relaxation times are important ingredients of the second order hydrodynamics whose success in heavy ion phenomenology is unquestioned. Unlike viscosites themselves, field theoretical calculations of the relaxation times are hard to come by in literature, especially for the bulk relaxation time. In this talk, we report two field-theoretical analyses involving the shear and the bulk relaxation time. First, by carefully examining the analytic structure of the stress-energy tensor response functions, we have been able to derive, for the first time, a Kubo formula involving both the shear and the bulk relaxation times. Second, by evaluating the Kubo formula within the massless scalar theory, we have so far been able to calculate the shear relaxation time in a simple form. We will then show how this calculation can be extended to calculate the bulk relaxation time as well.
-
Physics Colloquium
"Low-energy Precision Physics and the Role of Lattice QCD"
Presented by Harmut Wittig, University of Mainz
Tuesday, November 15, 2016, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: 'Peter Petreczky'
The particle content of the Standard Model has been completely established following the discovery of the Higgs boson. While the Standard Model describes all known phenomena in accelerator-based experiments, many important questions are left unanswered. In this talk I describe several attempts to detect signals for physics beyond the Standard Model using precision experiments at low energies. Special attention is given to the anomalous magnetic moment of the muon and the role of lattice QCD in quantifying the hadronic uncertainties in its theoretical prediction.
-
Nuclear Physics Seminar
"Is there a low p_T anomaly in the pion momentum spectrum at LHC?"
Presented by Pasi Huovinen, University of Wroclaw
Tuesday, November 15, 2016, 11 am
Small Seminar Room, Bldg. 510Hosted by: 'Oleg Kjeld'
The low p_T part of the pion spectrum measured by the ALICE collaboration has turned out to be very difficult to reproduce using conventional fluid dynamical approaches. In this talk I discuss how the finite width of rho mesons affects the yield of rhos and the distribution of pions originating from rho decays, and how inclusion of the finite width in the description of resonances may help to explain the low p_T pion data.
-
Particle Physics Seminar: SB/BNL Joint Cosmo Seminar
"Revealing CII Emission with LSS Cross-correlations"
Presented by Anthony Pullen, NYU
Thursday, November 10, 2016, 3 pm
Small Seminar Room, Bldg. 510Hosted by: '''''Anze Slosar'''''
The CII emission line tends to be the brightest line in star-forming galaxies, making it an ideal tracer of large-scale structure. Through the method of intensity mapping, astronomers hope to map CII emission at cosmological redshifts and large volumes, making CII and unprecedented probe of cosmology and reionization. However, the various models of the expected CII emission are highly uncertain by orders of magnitude, limiting our ability to predict how well potential CII surveys could probe large-scale structure. In this talk, I will present our measurement of excess emission from large scales at redshift z=2.5 potentially attributable to CII emission. This excess emission was measured by cross-correlating the 545 GHz broad-band microwave map from the Planck satellite and high-redshift quasars from the Sloan Digital Sky Survey. I will also discuss future opportunities with CII intensity mapping.
-
Environmental & Climate Sciences Department Seminar
"Observational constraints on mixed-phase clouds imply higher climate sensitivity"
Presented by Ivy Tan, Yale Univ.
Thursday, November 10, 2016, 11 am
Conference Room Bldg 815EHosted by: 'Robert McGraw'
Mixed-phase clouds are comprised of both liquid droplets and ice crystals. For a given total water content, mixed-phase clouds with higher liquid water contents are optically thicker and therefore more reflective to sunlight compared to those with higher ice water contents. This is due to the fact that liquid droplets tend to be smaller in size and more abundant than ice crystals in Earth's atmosphere. Given the ubiquity of mixed-phase clouds, the ratio of liquid to ice in these clouds is expected to be important for Earth's radiation budget. We determine the climatic impact of thermodynamic phase partitioning in mixed-phase clouds by using five pairs of simulations run with CAM5/CESM. Of the five pairs of simulations, the thermodynamic phase partitioning of two of the simulations were constrained to better agree with observations from CALIPSO. The other three pairs of simulations include a control simulation, as well as an upper and lower bound simulation with maximally high and low amounts of mixed-phase cloud liquid fractions. An analysis of the simulations shows that a negative "cloud phase feedback" that occurs due to the repartitioning of cloud droplets and ice crystals under global warming is weakened when mixed-phase clouds initially contain a higher amount of liquid. Simulations that exhibited weaker cloud phase feedbacks also had higher climate sensitivities. The results suggest that an unrealistically strong cloud phase feedback leading to lower climate sensitivities may be lurking in the many climate models that underestimate mixed-phase cloud liquid fractions compared to observations.
-
Particle Physics Seminar
"An improved ultracold neutron bottle for measuring the neutron lifetime"
Presented by Dr. E. Adamek
Thursday, November 10, 2016, 10 am
Small Seminar Room, Bldg. 510Hosted by: '''Xin Qian'''
The neutron beta decay lifetime is an important parameter in theories of weak interaction and big bang nucleosynthesis. To this end, many experiments over the past several decades have sought to improve the precision of this value. Ultracold neutrons, or UCN, are neutrons with extremely low energies which can be contained by material walls; these have provided us with a useful tool in measuring the neutron lifetime. The most recent set of experiments have demonstrated a 6sigma discrepancy between two lifetime values, each obtained using a different method of measurement. The UCNtau experiment at Los Alamos Neutron Science Center, is a bottling experiment which is designed to hold UCN within a 600 liter magnet-lined bowl to store the neutrons through magnetogravitational trapping. The open topped nature of the storage vessel allows for detectors to be lowered into the UCN volume to take in-situ measurement of the surviving UCN after varying storage times. This talk will cover newly presented results from the most recent UCNtau experiment data.
-
Physics Colloquium
"Skyrmions and Nuclei"
Presented by Nick Manton
Tuesday, November 8, 2016, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: 'Robert Pisarski'
Nuclear forces are mediated by pions. As pions are light compared to nucleons and other mesons, they are treated as approximate Goldstone bosons in an effective field theory (EFT) with spontaneously broken SO(4) chiral symmetry. Generically, the nonlinear field equations of EFT have topological soliton solutions called Skyrmions, which we identify as the intrinsic structures of nucleons or larger nuclei. The quantum states of the unit-winding, spherical Skyrmion represent protons and neutrons with spin half. Skyrmions of many higher winding numbers are also known, having beautiful symmetries, and sometimes showing alpha-particle or other clustering. The classical solutions have definite location, orientation, and pion field orientation, so we quantize the collective coordinates to obtain states with definite momentum, spin and isospin. A Skyrmion's symmetry restricts its allowed spin/isospin combinations (Finkelstein—Rubinstein constraints). The recent inclusion of vibrational degrees of freedom has helped to create a reasonable model for Oxygen-16 and its excited states.
-
Nuclear Physics & RIKEN Theory Seminar
"Glue spin from lattice QCD"
Presented by Yi-Bo Yang, University of Kentucky
Friday, November 4, 2016, 2 pm
Small Seminar Room, Bldg. 510Hosted by: '''Heikki Mantysaari'''
I will present the result of the glue spin in proton from the lattice QCD simulation, and also the renormalization and matching issues. The lattice calculation is carried out with valence overlap fermions on 2+1 flavor DWF gauge configurations on four lattice spacings and four volumes including an ensemble with physical values for the quark masses. The glue spin $S_G$ in the $\overline{\text{MS}}$ scheme is obtained with the 1-loop perturbative matching. I will also discuss the generic strategy and possible difficulties of calculating the glue helicity on the lattice, from the large momentum effective theory to the lattice simulations.
-
Condensed-Matter Physics & Materials Science Seminar
"Surface X-ray Diffraction for Operando Characterization of Chemical Reactions on Surfaces""
Presented by Roberto Felici, Istituto SPIN - CNR, Italy
Friday, November 4, 2016, 11 am
ISB Bldg. 734, Sem. Rm. 201 (upstairs)Hosted by: ''''Ian Robinson''''
X-rays are an ideal probe for studying structural properties of matter and, thanks to the brilliance of synchrotron sources, they are also employed to determine the atomic structure and morphology of surfaces and interfaces. Surface x-ray diffraction has been originally developed to determine the static structure of surfaces. However with the development of x-ray sources, detectors and analysis tools it is now possible to characterise in detail processes which occur at surfaces. Aim of this talk is to present recent results obtained at the id03 surface diffraction beamline of the ESRF dealing with the in-situ characterization of the structure and morphology of a catalyst during a surface reaction. Examples will deal with heterogenous catalytic oxidation of CO on single crystal surfaces /1,2/ and supported nanoparticles /3/ References 1 R. van Rijn et al., Phys. Chem. Chem. Phys. 13 (2011) 13167 2 B.L. Hendriksen et al., Nat. Chem. 2 (2010) 730 3 O. Balmes, et al., Phys. Chem.Chem. Phys. 14 (2012) 4796
-
RIKEN Lunch Seminar
"Form Invariance, Topological Fluctuations and Mass Gap of Yang-Mills Theory"
Presented by Yachao Qian, Stony Brook University
Thursday, November 3, 2016, 12:30 pm
Building 510, Room 2-160Hosted by: ''Hiromichi Nishimura''
We study the quantum Yang-Mills theory in the presence of topologically nontrivial backgrounds. The topologically stable gauge fields are constrained by the form invariance condition and the topological properties. Obeying these constraints, the known classical solutions to the Yang-Mills equation in the 3- and 4-dimensional Euclidean spaces are recovered, and the other allowed configurations form the nontrivial topological fluctuations at quantum level. Together, they constitute the background configurations, upon which the quantum Yang-Mills theory can be constructed. We demonstrate that the theory mimics the Higgs mechanism in a certain limit and develops a mass gap at semi-classical level on a flat space with finite size or on a sphere.
-
Nuclear Physics Seminar
"Photon-tagged jet production in 5.02 TeV Pb+Pb and pp"
Presented by Peter Steinberg, BNL
Tuesday, November 1, 2016, 11 am
Small Seminar Room, Bldg. 510Hosted by: ''Jia Jiangyong''
Nuclear collisions which produce a high transverse momentum (p_T) prompt photon offer a useful way to study the dynamics of the hot, dense medium produced in these events. Because photons do not carry color charge, they are unaffected by the hot, dense medium. Thus, the outgoing photon serves as a tag of the initial parton flavors, and measures the initial parton pT before they are quenched by their passage through the medium In 2015, ATLAS sampled 0.49 nb-1 and 26 pb-1 of Pb+Pb and pp data at 5.02 TeV, respectively, with a high-level photon trigger that selects p_T>25 GeV photons with high efficiency. The larger prompt photon cross-section and integrated luminosity with respect to 2.76 TeV data allow for new, differential studies of photon-jet correlations. In this talk, ATLAS results on photon-jet azimuthal and pT balance will be presented using pT > 60 GeV photons and R=0.4, pT > 30 GeV jets. Double-differential distributions of the jet-to-photon p_T ratio, x_Jg, and of the azimuthal difference, $\Delta\phi$, will be presented as a function of photon p_T and event centrality.
-
C-AD Accelerator Physics Seminar
"The REDTOP Experiment: Rare Eta Decays with a TPC for Optical Photons"
Presented by Dr. Corrado Gatto, FNAL and INFN
Friday, October 28, 2016, 10 am
Large Conference Room Bldg. 911BHosted by: '''Wolfram Fischer'''
The eta meson is almost unique in the particle universe since it is a Goldstone boson and the dynamics of its decay are strongly constrained. Because the eta has no charge, decays that violate conservation laws can occur without interfering with a corresponding current. The integrated eta meson samples collected in earlier experiments have been less than 1e8 events, limiting considerably the search for such rare decays. A new experiment, REDTOP, is being proposed at the proton booster of Fermilab with the intent of collecting more than 1e12 triggers/year for studies of rare eta decays. Such statistics are sufficient for investigating several symmetry violations, and for searches for new particles beyond the Standard Model. The physics program, the accelerator systems and the detector for REDTOP will be discussed during the seminar.
-
Condensed-Matter Physics & Materials Science Seminar
"Driven Dirac Materials"
Presented by Alexander Balatsky, Los Alamos National Laboratory
Thursday, October 27, 2016, 1:30 pm
Bldg. 734, ISB Seminar Rm. 201 (upstairs)Hosted by: 'Robert Konik'
Dirac Materials exhibit nodes in the spectra that result in the strong energy dependence of the Density of States (DOS). Collective many body instabilities in Dirac Materials are controlled by the dimensionless DOS. Hence the driven and nonequilibrium Dirac Materials offer a platform for investigation of collective instabilities of Dirac nodes via controlled tuning of the coupling constants with drive. I will present the results of investigation of the many body instabilities, like excitonic instabilities, in driven Dirac Materials. Recent optical pump experiments are consistent with the creation of long lived states away from equilibrium in Dirac Materials.
-
RIKEN Lunch Seminar
"Hybrid approach to relativistic heavy-ion collisions at the RHIC BES energies"
Presented by Chun Shen, BNL
Thursday, October 27, 2016, 12:30 pm
Building 510, Room 2-160Hosted by: '''Hiroshi Oki'''
Using a hybrid (viscous hydrodynamics + hadronic cascade) framework, we model the bulk dynamics of relativistic heavy-ion collisions at the RHIC BES collision energies, including the effects from non-zero net baryon current and its dissipative diffusion during the evolution. The framework is in full 3+1 dimension which allows us to study the non-trivial longitudinal structure and dynamics of the collision systems, for example, the baryon stopping/transport. The collision energy dependence of hadronic chemistry, identified particle spectra, anisotropic flows, and HBT radii is studied from 200 GeV to 19.6 GeV. Effects of breaking boost-invariance, net-baryon current, and its related diffusion on hadronic observables will be addressed. Finally, flow prediction for recent d+Au collisions at the BES energies will be presented within the same framework.
-
Special Nuclear Theory/RIKEN seminar
"A new relativistic viscous hydrodynamics code for high-energy heavy-ion collisions"
Presented by Chihi Nonaka, Nagoya University, Japan
Wednesday, October 26, 2016, 11 am
Small Seminar Room, Bldg. 510Hosted by: ''Chun Shen''
Relativistic hydrodynamic simulations play a key role in exploring the QGP bulk property and the QCD phase transition from analyses of high-energy heavy-ion collisions at RHIC and LHC. From the intensive study based on relativistic viscous hydrodynamic models with event-by-event initial fluctuations, we can extract detailed information of the bulk feature of the QGP such as transport coefficients and the QCD equations of states. In the quantitative analyses of the QGP property, high-precision numerical treatment on the hydrodynamic calculation is important. Recently, we developed a new 3+1 dimensional relativistic viscous hydrodynamics code in Cartesian coordinates. In the algorithm, we use a Riemann solver based on the two-shock approximation which is stable under existence of large shock waves. We extend the algorithm in Cartesian coordinates to that in Milne coordinates so that we can efficiently apply it to the analyses of relativistic heavy-ion collisions. We check the correctness of the numerical algorithm by comparing numerical calculations and analytical solutions in various problems for ideal and viscous fluids. The new numerical scheme is stable even with small numerical viscosity, which is very important to discuss the physical viscosities at RHIC and LHC.
-
Physics Colloquium
"From Stars to Nuclei and Back: Our Cosmic Origin and the Exascale Challenge to Find It"
Presented by Tony Mezzacappa, University of Tennessee
Tuesday, October 25, 2016, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: 'Peter Petreczky'
We learn in elementary school that the elements in the Periodic Table are the building blocks of our world, including our very bodies. But from where do the elements come? This is among the most basic questions we can ask, yet the precise answer remains elusive. We witness the cycle of life in our daily lives, everywhere on Earth. This is no less true in the Universe. With the exception of the lightest elements such as hydrogen and helium, elements are made in stars. As stars evolve and die, these elements pepper the interstellar medium, from which new stars, and planets, – in particular, our solar system – form. We understand the essential elements of this cycle – from stellar birth, life, and death, to the formation of the elements, to the formation of new stars and planets including those elements, to ultimately the origin of our solar system and life on Earth given those elements. But pieces of the puzzle are missing. We do not yet understand how certain stars that are factories for many of the elements, die, nor do we know the precise origin of half the elements heavier than iron, although we have narrowed down the list of possible sites. Today's colloquium will focus on the death of massive stars in catastrophic explosions known as core collapse supernovae. Such supernovae provide the lion's share of the elements between oxygen and iron, and are considered a potential site for the origin of half the elements heavier than iron. Arguably, they are the single most important source of elements in the Universe. Such supernovae present us with a general relativistic, radiation magneto-hydrodynamic – i.e., a multi-physics – environment to model. Further richness and complexity is added by the fact that the macroscopic evolution of such a system is governed in no small part by the high-density, neutron-rich, nuclear matter at the core of the supernova and by the microscopic interaction of radiation in the form of neutrinos with th
-
Nuclear Physics Seminar
"Recent Experimental Results on QCD Factorization Breaking of Nonperturbative Functions"
Presented by Joe Osborn
Tuesday, October 25, 2016, 11 am
Small Seminar Room, Bldg. 510Hosted by: 'Jin Huang'
In the last two decades the study of nucleon structure has shifted from a one-dimensional picture to exploring the dynamic three-dimensional structure of partons within the nucleon. In the transverse-momentum-dependent framework, nonperturbative parton distribution functions (PDFs) and fragmentation functions (FFs) explicitly carry dependence on partonic transverse momentum rather than only the collinear momentum of the parton with respect to the hadron or produced hadron with respect to the fragmenting parton. The recent interest in the transverse structure of the nucleon has largely been motivated by the novel phenomenological consequences that have been predicted for transverse-momentum-dependent nonperturbative functions. Contrary to the collinear framework, certain transverse-momentum-dependent PDFs are predicted to be process dependent. Additionally, factorization breaking has been predicted in hadronic collisions where a final-state hadron is measured and the observable is sensitive to nonperturbative transverse momentum. This prediction has the interesting quantum mechanical consequence that partons are correlated with each other across the bound state hadrons, rather than being identified with individual PDFs and FFs. Recent results from the PHENIX experiment at the Relativistic Heavy Ion Collider will be shown which investigate effects that are predicted to be sensitive to the nonperturbative factorization breaking.
-
Condensed-Matter Physics & Materials Science Seminar
"Creating Spatially Ordered States in Monolayer Graphene"
Presented by Abhay Pasupathy, Columbia University
Friday, October 21, 2016, 1:30 pm
ISB Bldg. 734, Conf. Rm. 201 (upstairs)Hosted by: 'Cedomir Petrovic'
Electrons in graphene at the Fermi level have chirality or handedness that arises from the honeycomb structure in real space. This chirality is responsible for many of the fascinating electronic properties of graphene such as Klein tunneling. In this talk, I will describe two related scanning tunneling microscopy experiments that probe the chiral nature of the electronic states in graphene. First, I will describe an experiment where we observe the chiral symmetry of graphene to be broken, resulting in a bond-ordered phase called Kekule order. I will show that this new phase in monolayer graphene can be induced by adatoms on the surface of graphene which interact electronically with each other. In a related experiment, I will describe the electronic structure of graphene in the presence of a circular potential well that separates the sheet into p (hole) and n (electron) doped regions. Electrons in these wells spend a finite amount of time before transitioning out of the well, resulting in quasibound states that can be measured in scanning tunneling spectroscopy. Due to the chirality of the electrons in graphene, the transition probabilities at the p-n junction are governed by the physics of Klein tunneling, which can be understood from the details of the energies and wavefunctions of the quasibound states observed in experiment.
-
Particle Physics Seminar
"Large area GEM detectors with zigzag readouts"
Presented by Aiwu Zhang, Florida Institute of Technology
Thursday, October 20, 2016, 3 pm
Small Seminar Room, Bldg. 510Hosted by: 'Xin Qian'
Gaseous Electron Multiplier (GEM) detectors have been widely studied and applied in many experiments. The so called zigzag readout has been studied for reading out large area GEM detectors for tracking purposes. Using of the zigzag readout can significantly reduce number of electronic channels and hence the cost of a detector while still preserving good spatial resolution on a detector. In this presentation, I will first briefly review the GEM detectors and their applications, then I will focus on the R&D activities on GEM detectors with zigzag readout for tracking at a future electron ion collider (EIC), I'll also cover some potential applications of large area GEM detectors and the zigzag readout for other experiments.
-
RIKEN Lunch Seminar
"Chiral magnetic effect and anomalous transport from real-time lattice simulations"
Presented by Niklas Mueller, Heidelberg University
Thursday, October 20, 2016, 12:30 pm
Building 510, Room 2-160Hosted by: '''Hiroshi Oki'''
We present a first-principles study of anomaly induced transport phenomena by performing real-time lattice simulations with dynamical fermions coupled simultaneously to non-Abelian SU(Nc) and Abelian U(1) gauge fields. Investigating the behavior of vector and axial currents during a sphaleron transition in the presence of an external magnetic field, we demonstrate how the interplay of the chiral magnetic and chiral separation effect leads to the formation of a propagating wave. We further analyze the dependence of the magnitude of the induced vector current and the propagation of the wave on the amount of explicit chiral symmetry breaking due to finite quark masses. Further we perform simulations using overlap-fermions for the first time in real-time, showing that in the classical statistical regime they can be related to the Wilson formulation.
-
Nuclear Physics Seminar
"Phase diagram of the strongly interacting matter in an effective field theory approach"
Presented by Gyorgy Wolf
Tuesday, October 18, 2016, 11 am
Small Seminar Room, Bldg. 510Hosted by: 'Oleg Eyser'
In the framework of an SU(3) (axial)vector meson extended linear sigma model with additional constituent quarks and Polyakov loops, we investigate the effects of (axial)vector mesons on the chiral phase transition. The parameters of the Lagrangian are set at zero temperature and we use a hybrid approach where in the effective potential the constituent quarks are treated at one-loop level and all the mesons at tree-level. We have four order parameters, two scalar condensates and two Polyakov loop variables and their temperature and baryochemical potential dependence are determined from the corresponding field equations. We investigate the thermodynamics of the system, and at zero temperature we compare our results with lattice calculations. We calculate th phase diagram and the scalar meson masses in the hot and dense medium.
-
RIKEN Lunch Seminar
"Kibble-Zurek dynamics and universal off-equilibrium scaling of critical cumulants in the QCD phase diagram"
Presented by Raju Venugopalan, BNL
Thursday, October 13, 2016, 12:30 pm
Building 510, Room 2-160Hosted by: ''Hiroshi Oki''
We exploit the universality between the QCD critical point and the three dimensional Ising model to derive closed form expressions for non-equilibrium critical cumulants on the crossover side of the critical point. Novel expressions are obtained for the non-Gaussian Skewness and Kurtosis cumulants; our results reveal that they can differ both in magnitude and sign from equilibrium expectations. We show further that key elements of the Kibble-Zurek framework of non-equilibrium phase transitions can be employed to describe the dynamics of these critical cumulants. As a consequence, observables sensitive to critical dynamics in heavy-ion collisions are expressible as universal scaling functions and thereby provide powerful model independent guidance in searches for the QCD critical point.
-
Nuclear Physics Seminar
"Transverse polarization of Lambda/anti-Lambda in e+e- annihilation at Belle and the K-Long muon (KLM) system of Belle-II detector"
Presented by Yinhui Guan, Indiana University
Tuesday, October 11, 2016, 11 am
Small Seminar Room, Bldg. 510Hosted by: 'Oleg Eyser'
Spontaneous Lambda polarization has been observed in unpolarized pp collisions years ago while the precise mechanism behind it remains unknown. It is assumed that the so called polarizing Fragmentation Function(FF) plays a important role in this effect. The polarizing FF is of great interest not only because it is strongly connected to the spin structure of hadrons, but also it is chiral-even and the sign is possible to be unambiguously measured so it provides a unique opportunity to test the universality of the FFs. The large e+e- annihilation data sample collected by the Belle experiment at the KEKB storage ring allows a precision study of the production of transversely polarized hyperons and check our current understanding of the associated QCD dynamics. The measurement of transverse Lambda/anti-Lambda polarization in e+e- annihilation in the inclusive Lambda production processes at Belle will be presented and discussed. The Belle II detector and SuperKEKB, the upgrade of Belle detector and KEKB collider, are being constructed at the KEK laboratory in Tsukuba, Japan. The K-Long and muon system of Belle II, which provides the K-Long and muon identification, consists of an alternating sandwich iron plates and active detector elements located outside of the superconducting solenoid. The Belle KLM based on glass-electrode resistive plate chambers(RPC) has demonstrated good performance. However, the long dead time of the RPCs during the recovery of the electric field after a discharge significantly reduces the detection efficiency under high backgrounds fluxes. So the endcap RPCs and two inner layers of barrel RPCs will be retired and replaced with scintillators in Belle II. This talk will introduce the Belle-II detector, mainly KLM system and the related offline software, KLM alignment and the current status of cosmic ray test (CRT).
-
Condensed-Matter Physics & Materials Science Seminar
"X-ray Imaging via Bragg CDI: From Ultrafast Physics to Defect Dynamics"
Presented by Andrew Ulvestad, Argonne National Laboratory
Friday, October 7, 2016, 11 am
ISB Bldg. 734, Conf. Rm. 201 (upstairs)Hosted by: ''Ian Robinson''
Bragg coherent diffractive imaging is an emerging x-ray imaging technique capable of resolving both defect and ultrafast dynamics in nanocrystals with three-dimensional detail and nanometer resolution. This ability to study single nanocrystals in their reactive environments opens new insight into a broad range of materials science questions, including how to improve materials that convert heat into electricity, understanding degradation in advanced battery cathodes, and probing the structure-stability relationship in fuel cell catalysts. Here I will discuss Bragg CDI studies of phonon dynamics in Zinc Oxide and defect dynamics in thin film grains driven by temperature. Finally, I will touch on future directions for BCDI with the anticipated increase in coherent flux at upgraded synchrotrons.
-
RIKEN Lunch Seminar
"Complex spectrum of QCD at finite density"
Presented by Hiromichi Nishimura, RBRC
Thursday, October 6, 2016, 12:30 pm
Building 510, Room 2-160Hosted by: ''Hiroshi Oki''
We consider the effective action of the Polyakov loop at finite temperature and density. Using simple models, we show two novel manifestations of the sign problem in QCD: the non-hermitian transfer matrix and the complex saddle point. As a result the mass matrix associated with the Polyakov loop becomes complex, and it gives rise to damped oscillatory behavior in Polyakov loop correlation functions, which reflects oscillatory behavior in the quark-number density reminiscent of density-density correlation functions in liquids. The complex spectrum should be observable in lattice simulations of QCD and may provide a test for finite-density algorithms.
-
Center for Functional Nanomaterials Seminar
"Reversed Nanoscale Kirkendall Effect in Au-InAs Hybrid Nanoparticles"
Presented by Anatoly I. Frenkel, Department of Materials Science and Engineering, Stony Brook University / Chemistry Department, Brookhaven National Laboratory
Thursday, October 6, 2016, 11 am
Bldg 735, Conference Room AHosted by: ''Eric Stach''
Metal-semiconductor hybrid nanoparticles (NPs) have synergistic properties that have been exploited in photocatalysis, electrical, and optoelectronic applications. Rational design of hybrid NPs requires the knowledge of the underlying mechanisms of diffusion of the metal species through the nanoscale semiconductor lattice. One extensively studied process of diffusion of two materials across the nanoparticle surface is known as the nanoscale Kirkendall effect. There, an atomic species A with the lower diffusion rate enters the nanocrystal slower than the B species diffusing from the nanocrystal outward. As a result, voids are formed in B, providing an interesting avenue for making hollow nanocrystals. We used time-resolved X-ray absorption fine-structure spectroscopy, X-ray diffraction and electron microscopy to monitor the diffusion process of Au atoms through InAs nanocrystals in real time. In this system the diffusion rate of the inward diffusing species (Au) is faster than that of the outward diffusion species (InAs), which results in the formation of a crystalline metallic Au core surrounded by an amorphous, oxidized InAs shell with voids in it. These observations indicate that in hybrid Au-InAs NPs the rarely observed "reversed nanoscale Kirkendall effect" is in play. It presents a potentially new way to synthesize unique nanoscale core-shell structures.
-
Condensed-Matter Physics & Materials Science Seminar
"The numerical renormalization group as a viable multi-band impurity solver for dynamical mean-field theory"
Presented by Katharina Stadler, Ludwig-Maximilians-Universitaet Muenchen, ASC, Germany
Wednesday, October 5, 2016, 1:30 pm
Bldg. 734, ISB Conference Room 201 (upstairs)Hosted by: 'Gabi Kotliar'
In my talk I will present the numerical renormalization group (NRG) as a viable multi-band impurity solver for dynamical mean-field theory (DMFT). NRG offers unprecedented real-frequency spectral resolution at arbitrarily low energies and temperatures. It is thus perfectly suited to study "Hund metals" [1], which show - in experiments and theoretical DMFT calculations - puzzling behavior at unusually low energy scales, like Fermi-liquid behavior at low temperatures, a coherence-incoherence crossover with increasing temperature [2, 3] and fractional power laws for the imaginary part of the Matsubara self-energy in the incoherent regime, discovered already early on with continuous time quantum Monte Carlo (CTQMC) as DMFT solver [3]. I will explicitly demonstrate the advantages of NRG+DMFT in the context of a channel-symmetric three-band Anderson-Hund model on a Bethe lattice at 1/3 filling (with NRG exploiting the non-abelian SU(3) channel symmetry to reduce numerical costs) [4]. In contrast to CTQMC, our NRG+DMFT calculations finally settled the existence of a Fermi-liquid ground state. We further revealed new important insights: our real-frequency one-particle spectral function shows a coherence-incoherence crossover (driven by Hund J rather than Hubbard U) and strong particle-hole asymmetry, which leads to the above-mentioned apparent fractional power laws; two-stage screening, where spin screening occurs at much lower energies than orbital screening ("spin-orbital separation"); and zero-temperature spectral properties that are similar with or without DMFT self-consistency, in contrast to Mott-Hubbard systems, where the DMFT self-consistency opens a gap. A recent reformulation of NRG, called "interleaved NRG" (iNRG) [5, 6] allows to tackle more realistic models of Hund metals where channel symmetries are generally broken (for example, due to crystal field splitting).
-
Nuclear Physics Seminar
"EoSization in holgraphic shockwave collision"
Presented by Maximilian Attems, University of Barcelona
Tuesday, October 4, 2016, 11 am
Small Seminar Room, Bldg. 510Hosted by: 'Oleg Eyser'
Ever since fast hydrodynamization has been observed in heavy ion collisions the understanding of the very early non-equilbrium stage of such collisions has been a topic of intense research. We use the gauge/string duality to model the creation of a strongly coupled Quark-Gluon plasma in a non-conformal gauge theory. This study is the first non-conformal holographic simulation of a heavy ion collision. We extract new physics as compared to the conformal case such as the non-trivial equation of state and the presence of a sizeable bulk viscosity. Non-conformality gives rise to an increase of the relaxation times of the resulting plasma. Furthermore, if the bulk viscosity is large enough then the plasma becomes well described by hydrodynamics before the equilibrium equation of state becomes applicable. This time we refer to as the EoSization time. This EoSization process is a new non-conformal relaxation channel involving the evolution of energy density and average pressure. It is exciting to see this new channel for bulk viscsosity values well below QCD critical temperature estimates.
-
Environmental & Climate Sciences Department Seminar
"Viscous organic aerosol particles and water uptake: From observations of internal diffusion fronts in single, levitated particles to estimating kinetic limitations under atmospheric conditions"
Presented by Dr. Ulrich Krieger, Institut für Atmosphäre und Klima, Zürich, Switzerland
Friday, September 30, 2016, 11 am
Conference Room Bldg 815EHosted by: 'Robert McGraw'
Field measurements in the recent past have shown that secondary organic aerosol (SOA) particles are often amorphous glasses or highly viscous liquids under dry and/or cold conditions. Chemical and physical processes occurring in the interior of the aerosol particle and at the gas/particle interface are influenced by the viscous state in which condensed-phase diffusion is slows down considerably. I will discuss measurements of water diffusion in single, levitated aerosol particles for a number of model systems of SOA. In particular, I will show how Mie-resonance spectroscopy allows to "image" diffusion fronts within these particles and discuss atmospheric implications of kinetic limitations of water uptake.
-
Particle Physics Seminar
"Sterile Neutrino Search at Daya Bay"
Presented by Dr. Wei Tang, BNL
Friday, September 30, 2016, 10 am
Small Seminar Room, Bldg. 510Hosted by: ''Xin Qian''
Daya Bay recently updated the light sterile neutrino searching results with 621 days of data. The new analysis has 3.6 times of statistics, improved energy calibration as well as the reduced backgrounds compared to the previous publication. The resulting limits on sin22theta14 are improved by approximately a factor of two over previous results and constitute the most stringent constraints to date in the Delta m2_41 < 0.2 eV2 region. The result is combined with those from MINOS and Bugey-3 experiments to constrain oscillation into light sterile neutrinos. The three experiments are sensitive to complementary regions of parameter space, enabling the combined analysis to probe regions allowed by the LSND and MiniBooNE experiments in 3+1 neutrino framework. Stringent limits on sin22theta_mue are set over six orders of magnitude in the sterile mass-squared splitting Delta m2_41. In this talk, I will show details of the recent update sterile neutrino search at Daya Bay, the reproduction of Bugey-3's results and the combination of Daya Bay, Bugey-3 and MINOS results.
-
Particle Physics Seminar
"Simulating the large-scale structure in different density environments"
Presented by Chi-Ting Chiang, Stony Brook University
Thursday, September 29, 2016, 3 pm
Small Seminar Room, Bldg. 510Hosted by: '''Anze Slosar'''
Understanding structure formation is one of the most important issues in modern cosmology. In particular, in the era of big astronomical data, connecting observation and theory is crucial to improve precision cosmology, and possibly probe new physics. The observables of large-scale structure, such as galaxy number density, generally depend on the density of the environment. This dependence can traditionally be studied by performing gigantic cosmological N-body simulations and measuring the observables in different density environments. Alternatively, we can perform so-called ``separate universe simulations,'' in which the effect of the environment is absorbed into the change of the cosmological parameters. In other words, an overdense universe is equivalent to a positively curved universe, and the structure formation would change accordingly. In this talk, I will introduce the separate universe mapping, and present how the power spectrum and halo mass function changes in different density environments, which are related to the squeezed-limit bispectrum and the halo bias, respectively. I will also discuss our recent progress on extending this approach to multiple fluids such as dynamic dark energy and massive neutrinos.
-
Particle Physics Seminar
"Measurement of muon g-2 and EDM with ultra-cold muon beam at J-PARC"
Presented by Dr. Tsutomu Mibe, KEK
Thursday, September 29, 2016, 10 am
Small Seminar Room, Bldg. 510Hosted by: 'Xin Qian'
The J-PARC E34 experiment aims to measure the anomalous magnetic moment (g-2) and electric dipole moment (EDM) of the positive muon with a novel technique utilizing an ultra-cold muons accelerated to 300 MeV/c and a 66 cm-diameter compact muon storage ring without focusing electric field. This measurement will be complementary to the previous BNL E821 experiment and upcoming FNAL E989 experiment with the muon beam at the magic momentum 3.1GeV/c in a 14 m-diameter storage ring. In this talk, I'd like to discuss the present status and prospects.
-
Physics Colloquium
"Synthetic gene circuits: New research tools for quantitative biology"
Presented by Gabor Balazsi, Stony Brook U
Tuesday, September 27, 2016, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: 'Peter Petreczky'
Synthetic biology is a new interdisciplinary field that designs and builds artificial biological systems, using principles from physics, engineering, and mathematics. Recent success stories include the massive, low-cost synthesis of the anti-malaria drug artemisinin, and the construction of genetic switches, oscillators and logic gates. In my laboratory we build synthetic gene circuits and use them as new research tools to precisely perturb cells and watch how they respond. This way, we hope to develop a predictive, quantitative understanding of biological processes such as microbial drug resistance and cancer. We have developed an expanding library of synthetic gene regulatory circuits first in yeast, and then in cancer cells for this purpose. I will illustrate through a few examples how we can gain a deeper, quantitative understanding of microbial drug resistance and cancer using synthetic gene circuits.
-
Nuclear Physics Seminar
"Hadronization studies at HERMES"
Presented by Charlotte Van Hulse, University of the Basque Country
Tuesday, September 20, 2016, 11 am
Small Seminar Room, Bldg. 510Hosted by: 'Oleg Eyser'
The HERMES experiment at DESY, Hamburg, collected data using the 27.6 GeV HERA electron/positron beam incident on a variety of gaseous targets, among others transversely polarized and unpolarized hydrogen as well as unpolarized deuterium, neon, krypton, and xenon. From the data taken with hydrogen and deuterium targets, charge-separated kaon and pion multiplicities in semi-inclusive deep-inelastic scattering were extracted. These allow the study of the spin-independent fragmentation of quarks into the identified hadrons. Hadronization in the nuclear environment studied via the analysis of multiplicities provides additional qualitative information on the space-time evolution of hadron formation. From the analysis of the azimuthal distribution of the produced hadrons, spin effects in hadronization can be studied, in particular the Collins fragmentation function, which describes the formation of a transversely polarized quark into an unpolarized hadron. The latter fragmentation function can also be accessed independently analyzing semi-inclusive deep-inelastic scattering events using the transversely polarized hydrogen target. The study of two-pion and two-kaon production from this same data sample provides access to a series of di-hadron fragmentation functions, including those in which the transverse spin of the fragmenting quark is transferred to the relative orbital angular momentum of the hadron pair. An overview of the results of the mentioned analyses as well as their possible interpretations will be presented.
-
Condensed-Matter Physics & Materials Science Seminar
"Interplay of structure, magnetism and superconductivity in the 112 Fe based superconducting family"
Presented by Ni Ni, UCLA
Thursday, September 15, 2016, 1:30 pm
Seminar Room, 2nd Fl, ISB Bldg. 734Hosted by: ''Robert Konik''
Both cuprates and Fe-based superconductors, the two known high Tc superconducting families, show rich emergent phenomena near the superconductivity (SC). To understand the mechanism of unconventional SC, it is crucial to unravel the nature of these emergent orders. The 112 Fe pnictide superconductor (FPS), Ca1−xRExFeAs2 (CaRE112), shows SC up to 42 K, the highest bulk Tc among all nonoxide FPS. Being an exceptional FPS where the global C4 rotational symmetry is broken even at room temperature, it is important to extract the similarities and di?erences between 112 and other FPS so that critical ingredients in inducing SC in FPS can be ?ltered. In this talk, I will review current progress in the study of 112. The comparison between Co doped CaLa112 and Co doped 10-3-8 will be made and the importance of interlayer coupling will be discussed.
-
RIKEN Lunch Seminar
"Quark Polarization at Small x"
Presented by Matt Sievert, BNL
Thursday, September 15, 2016, 12:30 pm
Building 510, Room 2-160Hosted by: ''Hiroshi Oki''
Parton distribution functions in the small-x limit have long been known to be dominated by gluon bremsstrahlung produced in the BFKL and BK / JIMWLK evolution mechanisms. This small-x gluon cascade generates high color-charge densities, leading to the effective semi-classical theory known as the color-glass condensate (CGC). While this unpolarized small-x evolution has been thoroughly studied, the evolution of the polarized parton distributions is much less understood. Using modern CGC techniques, we calculate the small-x evolution equations for the helicity distribution of polarized quarks. This polarized small-x evolution is quite different from the unpolarized evolution, bringing in much more complicated dynamics which transfer spin to small x. Although the quark polarization at small x is initially suppressed, strong evolution corrections substantially enhance the amount of spin at small x. By solving our equations (numerically, in the large-Nc limit), we compute the asymptotic behavior of the quark helicity at small x, and we discuss the implications of this result for the outstanding Proton Spin Puzzle.
-
Physics Colloquium
"Transport in QCD: A Theorist's View"
Presented by Guy Moore, University of Darmstadt
Tuesday, September 13, 2016, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: ''Robert Pisarski''
After summarizing the role of hydrodynamics in QCD and heavy ion physics, I will focus on what we know, theoretically, about the transport coefficients which enter hydrodynamics. I will focus on shear viscosity and heavy quark diffusion. I will explain the problems and limitations of the theoretical tools we have, and how we hope to push them a little farther — and better characterize their weaknesses.
-
Nuclear Physics Seminar
"Finite-Size Scaling of Susceptibility and Non-Gaussian Fluctuations Near the QCD Critical Point"
Presented by Roy Lacey, Stony Brook University
Friday, September 9, 2016, 2 pm
Small Seminar Room, Bldg. 510Hosted by: 'Matthew Sievert'
A major experimental theme at the Relativistic Heavy Ion Collider (RHIC), is the the study of observables that could signal the location and character of the critical endpoint (CEP) – the end point of the first-order coexistence curve in the temperature vs. baryon chemical potential (T, μB) plane of the phase diagram for Quantum Chromodynamics (QCD). I will show that Finite-Size Scaling of measurements linked to both the susceptibility and critical fluctuations, lead to scaling functions which provide a potent tool for locating and characterizing the CEP. A recent estimate of the location of the CEP and the associated critical exponents used to assign the order of the transition and its universality class will be presented as well.
-
Nuclear Physics Seminar
"Current state of nPDFs, LHC and future possibilities"
Presented by Pia Zurita, Universidade de Santiago de Compostela, Spain, Spain
Thursday, September 1, 2016, 2 pm
2-160Hosted by: 'Thomas Ullrich'
In the last years, significant progress has been made in obtaining nuclear PDFs (nPDFs) from data. In addition to the theoretical improvements routinely used in modern extractions of free proton PDFs, the most recent determinations of nPDFs have move towards truly global QCD analyses of nuclear effects. Furthermore, the end of the Run at the LHC I has shown promising results for the improvement of our knowledge on the nuclear medium. In this talk I will discuss the current state of nPDFs, comparing the most recent determinations, and address the possible impact of LHC and future colliders' data on the nPDFs.
-
Condensed-Matter Physics & Materials Science Seminar
"The first-principles study of structural, electronic, and magnetic properties of strongly correlated materials: DFT+DMFT approach."
Presented by Hyowon Park, University of Illinois
Thursday, August 25, 2016, 3 pm
Bldg. 734, ISB Conference Room 201 (upstairs)Hosted by: ''Neil Robinson''
Strongly correlated materials including transitional metal oxides and heavy fermion materials exhibit novel structural, electronic, and magnetic properties. The first-principles study of these unusual properties requires a theoretical description that goes beyond density functional theory to treat strong correlation effects properly. In this talk, I will show that the density functional theory plus dynamical mean field theory (DFT+DMFT) method enables realistic and quantitative calculations of those properties in good agreement with experimental spectroscopic measurements. First, I will clarify the nature of the insulating phase in bulk rare-earth nickelates using DFT+DMFT and determine the structural and metal-insulator phase diagram. I will also present DFT+DMFT results of structural and electronic properties in artificially structured LaNiO3/LaAlO3 superlattices under strains. Calculation results of layer-resolved orbital polarization will be compared to recent X-ray absorption spectroscopy data and analyzed in terms of structural and quantum confinement effects. Finally, I will show the momentum and frequency dependent magnetic excitation spectra in CePd3 computed using DFT+DMFT and explain that the calculated spectra based on realistic band excitations are in good agreement with the inelastic neutron scattering data measured in this material.
-
Nuclear Physics Seminar
"Multiplicity Fluctuations in Dilute-Dense Scattering"
Presented by A. H. Mueller, Columbia University
Friday, August 19, 2016, 2 pm
Small Seminar Room, Bldg. 510Hosted by: 'Matthew Sievert'
The general features of the event-by-event fluctuations of the multiplicity of gluons produced in the scattering of a dilute "hadron" off a large nucleus are discussed. Analytic calculations are possible in "semi-realistic" circumstances.
-
Condensed-Matter Physics & Materials Science Seminar
"Controlling the metal-insulator transition in LaNiO3"
Presented by Frederick Walker, Yale University
Thursday, August 18, 2016, 1:30 pm
Bldg. 734, ISB Bldg., Conf Room 201 (upstairs)Hosted by: 'Mark Dean'
New materials are needed to advance electronic, optical and energy materials beyond current technology trends. Perovskite oxides can potentially meet these needs due to their flexibility and unique functional properties. In bulk materials, these properties are accessed through modifications of physical and electronic structure through cation substitution in the perovskite lattice. An even larger phase space of properties and functionalities is possible when these materials are combined in thin film heterostructure form using molecular beam epitaxy. The sensitivity of the resulting properties on interface structure often dominates device function. Uncovering a microscopic understanding of emergent properties at such interfaces is challenging due to the small volume of material present. In this talk, we show how a combination of first principles theory and experiment can be used to develop a non-volatile, three terminal switch. The device is implemented by using the perovskite LaNiO3 as a conducting channel and a ferroelectric gate. The approach to developing this switch involves synchrotron x-ray characterization of picoscale structural distortions for LaNiO3 heterostructures, including LaNiO3-vacuum, LaNiO3-band insulator, and LaNiO3-ferroelectric. The consequences of the picoscale distortions are strong modulations of the measured electronic transport as a function of interface and ferroelectric polarization direction. Quantitative comparisons of the structure with first principles theory show excellent agreement. Theory provides an understanding of how the picoscale distortions at the interface result in changes in orbital occupation and band properties of both the nickelate and ferroelectric. These insights inspire new principles for designing ferroelectric heterostructures that show record non-volatile resistance modulations.
-
Special Nuclear Theory Seminar
"Scalar mesons in low-energy QCD and probing their properties within generalized linear sigma model"
Presented by Amir Fariborz, SUNY Institute of Technology at Utica
Tuesday, August 9, 2016, 11 am
Small Seminar Room, Bldg. 510Hosted by: 'Rob Pisarski'
Unlike the light pseudoscalar mesons, understanding the properties of light scalar mesons (particularly, their quark substructure) is known to be quite nontrivial. Scalar mesons are important from the theoretical point of view because they are effectively the Higgs bosons of QCD and induce chiral symmetry breaking, and therefore, are probes of the QCD vacuum. Scalars are also important from a phenomenological point of view, as they are crucial intermediate states in Goldstone boson interactions away from threshold; in a range of energy that is too high for a chiral perturbation theory framework, and too low in the context of the perturbative QCD. The physics of scalar mesons has a great impact on our understanding of important issues in strong interactions such as the diquarks, glueballs, hybrids, violation of isospin, low energy hadron phenomenology, instantons, and final-state interaction of pseudoscalar mesons. Moreover, physics of scalar mesons can provide significant insights outside its immediate focus of low-energy QCD such as, for example, in studies of decay Ds to f0(980) e+ ve or decay Bs to J/psi f0(980) measured by LHCb. In this talk, the status of the scalar mesons will be briefly reviewed and the generalized linear sigma model of low-energy QCD for understanding their properties will be presented. Specifically, the underlying symmetries (and their breakdown) for designing the generalized linear sigma model, as well as various contacts with experiment for fixing the free paremeters of the model will be discussed in some details. Several predictions for various low-energy processes as well as the application of this model to studies of heavier meson decays will be given, and directions for further extensions of the model will be discussed.
-
Nuclear Physics Seminar
"Polarization phenomena in the Drell-Yan process"
Presented by Werner Vogelsang, University of Tübingen
Friday, August 5, 2016, 2 pm
Small Seminar Room, Bldg. 510Hosted by: 'Matthew Sievert'
We present calculations of next-to-leading order corrections to the cross section and the single-longitudinal spin asymmetry for W boson production at RHIC. We also discuss decay lepton angular distributions in the Drell-Yan process at hadron colliders and in fixed-target experiments.
-
Particle Physics Seminar
"Study of the detection of supernova neutrinos"
Presented by Hanyu Wei, Tsinghua University
Friday, August 5, 2016, 10 am
Small Seminar Room, Bldg. 510Hosted by: 'Xin Qian'
A core-collapse supernova explosion would release an enormous amount of neutrinos, the detection of which could yield answers to many questions of supernova dynamics and neutrino physics. The collective neutrinos from all the past supernovae all over the universe (supernova relic neutrinos) are also observable, and their detection would provide us an insight of the stellar evolution and cosmology. In this talk, I will first introduce the supernova burst neutrinos as well as supernova relic neutrinos. Then, i will present the design, characteristics, and sensitivity of an online trigger system of supernova burst neutrinos at Daya Bay. I will also present a search for supernova burst neutrinos at Daya Bay using about 600 days of data. At last, a sensitivity study of the discovery potential for supernova relic neutrinos with a slow liquid scintillator will be presented, which is highly recommended to kilo-ton-scale detectors.
-
Particle Physics Seminar
"KamLAND-Zen and NuDot: The Future of Liquid Scintillator Detectors"
Presented by Lindley Winslow, MIT
Thursday, August 4, 2016, 3 pm
Small Seminar Room, Bldg. 510Hosted by: ''Xin Qian''
Large liquid-scintillator-based detectors have proven to be exceptionally effective for low energy neutrino measurements due to their good energy resolution and scalability to large volumes. The addition of directional information using Cherenkov light and fast timing would enhance the scientific reach of these detectors, especially for searches for neutrino-less double-beta decay. NuDot is a 1m3 prototype detector that will demonstrate this technique using fast photodetectors and eventually quantum-dot doped liquid scintillator. The ultimate goal is a measurement of two neutrino double-beta decay with direction reconstruction.
-
RIKEN Lunch Seminar
"Photon-jet Ridge at RHIC and the LHC"
Presented by Amir Rezaeian, The Federico Santa Maria Technical University
Thursday, August 4, 2016, 12:30 pm
Building 510, Room 2-160Hosted by: ''Hiroshi Oki''
I will talk about inclusive prompt photon and photon-jet production in p+A collisions at RHIC and the LHC. In particular, I show that photon-jet correlations in the Color Glass Condensate (CGC) picture exhibit long-range azimuthal collimation at near-side for low transverse momenta of the produced photon and jet in high-multiplicity events. These ridge-like features are strikingly similar to the observed ridge effect for di-hadron correlations at RHIC and the LHC. I show that correlations in the relative rapidity and the relative azimuthal angle between pairs of prompt photon and jet strongly depend on the gluon saturation dynamics at small-x kinematics and such measurements can help to understand the true origin of the observed di-hadron ridge in p+A collisions, and address whether the ridge is a universal phenomenon for all two particle correlations at high energy and high multiplicity events.
-
Center for Functional Nanomaterials Seminar
"Perovskite Photovoltaics and g-ray Radiation Detectors Research Highlights"
Presented by Deidra R. Hodges, Ph.D., University of Texas at El Paso
Wednesday, August 3, 2016, 11 am
CFN, Bldg 735, Conference Room A, 1st FloorHosted by: '''''Mircea Cotlet'''''
Perovskite Photovoltaics: Renewable energies are one of the most important components of the global new energy strategy. Utilizing the power of the sun is one of the most viable ways to solve the foreseeable world's energy crisis. With increasing attention toward carbon-neutral energy production, solar electricity, or photovoltaic (PV) technology, is the object of steadily growing interest. The International Energy Agency's technology roadmap estimates that by 2050, PV will provide ~ 11% of all global electricity production & avoid 2.3 gigatonnes of CO2 emissions per year. A new solar cell material has evolved with transformative potential with laboratory efficiencies of 19.7%. Perovskite absorber materials are very inexpensive to synthesize & simple to manufacture, making them an extremely commercially viable option. Solar cell efficiencies of devices using these materials have increased from 3.8% in 2009 to a certified 20.1% in 2015, making this the fastest-advancing solar cell technology to date. These devices are also known for their high photon absorptivity, ideal direct band gaps with superior carrier charge transports, & cost-effective modes of fabrication scalability. Gama-ray Radiation Detectors: Cadmium zinc telluride (Cd1-xZnxTe or CZT), a ternary semiconductor material is well suited for good charge collection efficiency & high energy resolution room temperature x- & gamma (γ) -ray radiation detectors. In addition, these detectors can be small in size & have fast timing characteristics. Key semiconductor material properties required for high efficiency, & high energy resolution radiation detectors operable at room temperature are a high atomic number, ideal bandgap & low leakage current, high carrier mobility-lifetime (µτ) product to ensure complete charge collection, & high-purity, homogenous, & defect-free. CZT is recognized as one of the leading materials for fabrication.
-
Nuclear Physics Seminar
"Azimuthal anisotropy and the distribution of linearly polarized gluons in DIS dijet production at high energy"
Presented by Adrian Dumitru, Baruch College
Friday, July 29, 2016, 2 pm
Small Seminar Room, Bldg. 510Hosted by: 'Matthew Sievert'
High Pt Dijet production in ep/eA DIS at small x (high energy) involves the expectation value of a trace of four Wilson lines, i.e. the quadrupole. At leading power the isotropic part can be expressed as the conventional Weizsacker-Williams gluon distribution. On the other hand, the distribution of linearly polarized gluons determines the amplitude of the ~ cos(2phi) anisotropy of the transverse momentum imbalance. I shall also discuss the operator that determines the next-to-leading power correction, its expectation value in a Gaussian theory (at large Nc), and the resulting .
-
Particle Physics Seminar
"Modeling electron- and neutrino-nucleus scattering in kinematics"
Presented by Vishvas Pandey, Ghent University
Thursday, July 28, 2016, 3 pm
Small Seminar Room, Bldg. 510Hosted by: ''Thomas Ullrich''
The accelerator-based neutrino-oscillation program, aimed for the measurement of oscillation parameters and observing the leptonic CP violation, is moving full steam ahead. However, the recent measurements have revealed unexpected and interesting neutrino interaction physics, and exposed the inadequacy of the relativistic Fermi gas (RFG) based Monte-Carlo generators (in describing neutrino-nucleus scatterings) resulting in large systematic uncertainties. A more detailed and careful neutrino-nucleus modeling, covering the whole experimental kinematical space, is inevitable in order to achieve the unprecedented precision goal of the present and future accelerator-based neutrino-oscillation experiments. In this talk, I will present a microscopic Hartree-Fock (HF) and continuum random phase approximation (CRPA) approach to electroweak scattering off nuclei from low energy (threshold) to the intermediate energy region. As a necessary check to test the reliability of this approach, I will first present a electron-nucleus (^12 C, ^16 O, ^40 Ca) cross section comparison (in the kinematics range of interest) with the data to validate the model. Then, I will present flux-folded (anti)neutrino cross section calculations and comparison with the measurements of MiniBooNE and T2K experiments. I will draw special attention to the contribution emerging from the low-energy nuclear excitations, at the most forward scattering bins, in the signal of MiniBooNE and T2K experiments and their impact on the non-trivial differences between muon-neutrino and electron-neutrino cross sections. These effects remain inaccessible in the (current) relativistic Fermi-gas (RFG) based Monte-Carlo generators.
-
Nuclear Physics Seminar
"Transport Functions from Fluid/Gravity Correspondence"
Presented by Michael Lublinsky, Ben-Gurion University
Friday, July 22, 2016, 2 pm
Small Seminar Room, Bldg. 510Hosted by: 'Matthew Sievert'
Transport coefficients in two systems are addressed via holographic methods originating from the AdS/CFT. The first system is a neutral conformal fluid. In linearised hydrodynamics, beyond shear viscosity, all order gradient expansion can be efficiently resummed into two momenta-dependent transport coefficient functions. The second system is an e/m current coupled via chiral anomaly to an axial U(1) current. The anomaly-free all order transport coefficients are resummed into three momenta-dependent functions, the diffusion function and two conductivities. Anomaly-induced transport, resummed to all orders, generalises the chiral-magnetic effect (CME) and related phenomena. Novel, anomaly-induced non-linear effects will be presented too.
-
Particle Physics Seminar
"Results from the Search for eV-Sterile Neutrinos with IceCube"
Presented by Dr. Carlos Arguelless Delgado, Massachusetts Institute of Technology
Thursday, July 21, 2016, 3 pm
Small Seminar Room, Bldg. 510Hosted by: ''Xin Qian''
The IceCube neutrino telescope at the South Pole has measured the atmospheric muon neutrino spectrum as a function of zenith angle and energy. Using IceCube's full detector configuration we have performed a search for eV-scale sterile neutrinos. Such a sterile neutrino, motivated by the anomalies in short-baseline experiments, is expected to have a significant effect on the $\bar{\nu_\mu}$ survival probability due to matter induced resonant effects for energies of order 1 TeV. This effect makes this search unique and sensitive to small sterile mixings. In this talk, I will present the results of the IceCube sterile neutrino search.
-
NSLS-II Friday Lunchtime Seminar Series
"Effect of Hydrophobic and Hydrophilic Silica Nano Particles on the Dynamics of Phospholipid Films, an XPCS Investigation"
Presented by Luigi Cristofolini, University of Parma, Italy
Friday, July 15, 2016, 12 pm
NSLS-II Bldg 744 (LOB 4), room 156Hosted by: 'L. Carr, S. Chodankar and B. Ocko'
-
Particle Physics Seminar
"MicroBooNE: marking a Nu era in Precision Neutrino Physics"
Presented by Dr. Sowjanya Gollapinni, KSU
Friday, July 15, 2016, 10 am
Small Seminar Room, Bldg. 510Hosted by: 'Jyoti Joshi'
The past few years have brought several remarkable neutrino-related discoveries and experimental anomalies indicating that these elusive particles might hold clues to some of the most profound questions in particle physics such as matter-antimatter asymmetry and the possibility of additional low-mass neutrino states. Further exploration of these clues require technological advances in neutrino detection. Liquid Argon Time Projection Chambers (LArTPCs) are imaging detectors that present neutrino interactions with the detail of bubble chambers, but with an electronic data acquisition and processing. Various efforts are ongoing at Fermi National Accelerator Laboratory (Fermilab) to develop this intriguing technology. MicroBooNE is a 170 ton LArTPC which recently started collecting data with Fermilab's Booster Neutrino Beam. In addition to addressing the recent low-energy electromagnetic anomaly observed by the MiniBooNE experiment, the exceptional particle identification capability of MicroBooNE will make it possible for the first time to measure low-energy (~1 GeV) neutrino cross-sections in argon with high precision thereby providing invaluable inputs to develop nuclear models needed for future long-baseline neutrino oscillation experiments. MicroBooNE is also leading the way for an extensive short-baseline neutrino physics program at Fermilab and also serves as a R&D project towards a long-baseline multi-kiloton scale LArTPC detector. This talk will start by giving a brief overview of LArTPC efforts at Fermilab, followed by a description of the MicroBooNE experiment, its current status and first physics results along with some future projections.
-
Particle Physics Seminar
"Physics with Taus at ATLAS"
Presented by Sarah Demers
Thursday, July 14, 2016, 3 pm
Small Seminar Room, Bldg. 510Hosted by: '''Michael Begel'''
Tau leptons are notoriously difficult particles to work with in the environment of a hadron collider due to their short lifetime and heavy enough mass for semi-hadronic decay. In this talk I will present the physics motivation for working with taus in spite of the challenges. And I will describe the work my group is involved with, from the first measurement of tau polarization at a hadron collider, to Higgs-tagging and searches for heavy, exotic particles. I will also describe the landscape for physics with taus at ATLAS as we look into Run2 and beyond.
-
RIKEN Lunch Seminar
"CME in Chiral Viscous Hydrodynamics"
Presented by Shuzhe Shi, Indiana University
Thursday, July 14, 2016, 12:30 pm
Building 510, Room 2-160Hosted by: 'Hiroshi Ohki'
Anomalous chiral transport processes, with the notable examples of Chiral Magnetic Effect (CME) and Chiral Magnetic Wave (CMW), are remarkable phenomena that stem from highly nontrivial interplay of QCD chiral symmetry, axial anomaly, and gluonic topology. The heavy ion collisions, in which topological fluctuations generate chirality imbalance, and very strong magnetic fields $|\vec{\bf B}|\sim m_\pi^2$ are present during the early stage of such collisions, provide a unique environment to study these anomalous chiral transport processes. Significant experimental efforts have been made to look for signals of CME and various other signals of anomalous chiral transport effects in heavy ion collisions. Crucial for such efforts, is the theoretical development of quantitative simulations based on hydrodynamics that incorporates chiral anomaly, implements realistic initial conditions and properly accounts for possible backgrounds. We will introduce our recent progress to understand CME qualitatively, based on a 2+1D viscous hydrodynamics framework
-
Nuclear Physics Seminar
"Modeling chiral criticality and its consequences for heavy-ion collisions"
Presented by Gabor Almasi, GSI
Friday, July 8, 2016, 2 pm
Small Seminar Room, Bldg. 510Hosted by: 'Matthew Sievert'
Fluctuations of conserved charges are important observables that offer insight into the phase structure of strongly interacting matter. Around critical points, such as the chiral critical endpoint of QCD, higher order cumulants of the relevant quantities show universal behavior. The universal behavior of baryon number cumulants can be studied in effective models that lie in the same universality class as QCD. Such a model is for example the Quark Meson model. In my talk I discuss what one can learn from effective field theory studies of fluctuations and present my results obtained using the Functional Renormalization Group method in the Quark Meson model.
-
Particle Physics Seminar
"Dark Matter in the Cosmos-The Hunt to find it in the Laboratory"
Presented by John D. Vergados
Thursday, July 7, 2016, 3 pm
Small Seminar Room, Bldg. 510Hosted by: 'Michael Begel'
Matter constitutes 30% of the energy content of the Universe. The remaining 70% is what is called dark energy, which exhibits unusual repulsive gravitational interactions. On the matter sheet, only 5% is of known nature, i.e. matter such as found in atoms, in stars, in planets etc. From observations on all astrophysical and cosmological scales we know that most of it, i.e. 25%, is dark matter (DM) of unknown nature. The nature of DM is one of the most important open problems in science. The ongoing hunt for DM is multi-pronged and interdisciplinary involving cosmology and astrophysics, particle and nuclear physics as well as detector technology. In this talk we will focus on the direct detection of the dark matter constituents, the so called weakly interacting massive particles (WIMPs), in underground labs. The detection consists of measuring the energy deposited in the detector by the recoiling nucleus, after its elastic collision with a WIMP (spin independent or spin induced). In obtaining the event rates one needs models about the WIMP interaction and density in our vicinity as well as its velocity distribution. No events have so far been observed, only exclusion plots on the nucleon cross sections have been obtained, which will be discussed. Since the expected rates are very small and the usual experimental signature is not different from that of the backgrounds, we will discuss some special signatures that might aid in the analysis of the experiments such as the time dependence of the signal (modulation effect) and the option of inelastic scattering, possible in some special targets, by detecting γ-rays following the de-excitation of the nucleus.
-
RIKEN Lunch Seminar
"Kondo effect in QCD"
Presented by Sho Ozaki, Keio University
Thursday, June 30, 2016, 12:30 pm
Building 510, Room 2-160Hosted by: ''Hiroshi Oki''
In condensed matter physics, Kondo effect is known as an enhancement of electrical resistance of impure metals with decreasing temperature/energy. This phenomenon is the first known example of asymptotic freedom in physics, which is found well before the discovery of that of QCD. Kondo effect is caused by the combination of the following ingredients: In addition to the existence of a heavy impurity, (i) Fermi surface, (ii) quantum fluctuations (loop effects), (iii) non-Abelian nature of interaction (e.g. spin-flip interaction in the case of condensed matter physics). In this talk, I will discuss Kondo effect realized in QCD. We found the characteristic behavior of Kondo effect in quark matter with heavy quark impurity. There, the color exchange interaction mediated by gluons plays the role of the third condition (iii) for the appearance of Kondo effect. Furthermore, we found a novel type of Kondo effect induced by strong magnetic fields. In addition to the fact that the magnetic field dose not affect the color degrees of freedom, dimensional reduction to 1+1 dimensions and degenerate quarks in lowest Landau level play essential role for the magnetically induced QCD Kondo effect.
-
Physics Colloquium
"Solving the World's Problems on the Back of a Cocktail Napkin"
Presented by Lawrence Weinstein, Old Dominion University
Tuesday, June 28, 2016, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: ''''Robert Pisarski''''
Why don't we all drive electric cars? Does it really matter if you don't recycle that plastic water bottle? If the Sun were made of gerbils, would the Earth be incinerated? How can we answer these questions without relying on experts? This talk will cover the principles of estimating, introduce the "Goldilocks" categories of answers, and then look at some of the big (and small) questions of our time, including: Paper or plastic? Gasoline or electric cars? Should we pee before flying?
-
Nuclear Physics Seminar
"Two Photon Exchange and the Proton Form Factor Problem"
Presented by Lawrence Weinstein, Old Dominion University
Tuesday, June 28, 2016, 11 am
Small Seminar Room, Bldg. 510Hosted by: 'Oleg Eyser'
The electromagnetic form factors of the proton as measured by polarized and unpolarized electron scattering experiments differ by up to a factor of three at large momentum transfer. Calculations show that this discrepancy can be reconciled by treating the interaction in 2nd Born Approximation, i.e., including two photon exchange (TPE). While calculation of TPE effects is highly model dependent, these effects can be measured directly by comparing elastic electron-proton and positron-proton scattering. Three experiments, TPE at Jefferson Lab, VEPP-3 at Novosibirsk, and OLYMPUS at DESY, measured this. VEPP-3 and OLYMPUS used alternating monochromatic e+ and e- beams in storage rings; TPE created a tertiary mixed simultaneous e+/e- beam covering a wide range of energies. This talk will present the proton form factor problem, the experimental effort to measure the positron-electron ratio (with special emphasis on the Jefferson Lab experiment), and the results.
-
Nuclear/Riken Theory Committee
"On Pressure Isotropization in Heavy-Ion Collisions"
Presented by Bin Wu, The Ohio State University
Friday, June 24, 2016, 2 pm
Small Seminar Room, Bldg. 510Hosted by: ''Soeren Schlichting''
In this talk, I would like to start with a brief introduction to non-equilibrium quantum field theory in the Schwinger-Keldysh formalism. This formalism provides a systematic way to study isotropization and other time-dependent non-equilibrium (and equilibrium) phenomena in heavy-ion collisions. I shall first discuss the foundation of classical field approximations (CSA), which is an important tool to study the evolution at very early stages. It is, however, found to be non-renormalizable. This helps us understand better the applicability of such an approximation. it is now well-known that isotropization can not be established before the breakdown of the CSA. We then use another approximation, the quasi-particle approximation (the Boltzmann equation), to study the isotropization in a scalar field theory. Our result shows explicitly the importance of quantum effects. Motivated by these observations, we have been studying whether the isotropization can be reached before the dense system of gluons, produced in the collisions of two big nuclei, becomes too dilute to be studied perturbatively in the Schwinger-Keldysh formalism. Some preliminary results shall be reported.
-
Physics Colloquium
"Sterile Neutrinos as the Origin of Dark and Baryonic Matter"
Presented by Mikhail Shaposhnikov, EPFL
Tuesday, June 21, 2016, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: 'Robert Pisarski'
I will discuss how three sterile neutrinos alone can simultaneously explain neutrino oscillations, the observed dark matter, and the baryon asymmetry of the Universe without new physics above the Fermi scale. The experimental prospects to search for these particles will be outlined.
-
Nuclear Physics Seminar
"The Quest for the Origin of the Proton's Sea"
Presented by Paul Reimer, Argonne National Lab
Tuesday, June 21, 2016, 11 am
Small Seminar Room, Bldg. 510Hosted by: 'Oleg Eyser'
The proton is a composite particle in which the binding force is responsible for the majority of its mass. To understand this structure, the distributions and origins of the quark-antiquark pairs produced by the strong force must be measured. The SeaQuest collaboration is using the Drell-Yan process to elucidate antiquark distributions in the proton and to study the modification of these distributions when the proton is held within a nucleus. Preliminary results based on a fraction of the anticipated final data set will be presented.
-
Nuclear Physics Seminar
"Lattice constraints on the thermal dilepton and photon rate"
Presented by Olaf Kaczmarek, Bielefeld University
Friday, June 17, 2016, 2 pm
Small Seminar Room, Bldg. 510We estimate the dilepton and photon production rate from an SU(3) plasma at temperatures of about 1.1 Tc to 1.5 Tc. Lattice results for the vector current correlator at zero and non-zero momenta are extrapolated to the continuum limit and analyzed with the help of phenomenological and perturbative input for the corresponding spectral functions. We compare our results with NLO weak-coupling results, hydrodynamics, and a holographic model. At vanishing invariant mass we extract the photon rate which for k>3T is found to be close to the NLO weak-coupling prediction. For k
-
Environmental & Climate Sciences Department Seminar
"High-Resolution Photography of Clouds from the Surface: Retrieval of Cloud Optical Depth down to Centimeter Scales"
Presented by Stephen Schwartz, Environmental and Climate Sciences Department
Thursday, June 16, 2016, 11 am
Conference Room, Bldg 815EInitial results are presented of a analysis of high resolution photographs of clouds at the ARM SGP site in July, 2015. A commercially available camera having 35-mm equivalent focal length up to 1200 mm (nominal resolution as fine as 6 µrad, which corresponds to 12 mm for cloud height 2 km) is used to obtain a measure of zenith radiance of a 40 m x 40 m domain as a two-dimensional image consisting of 3456 x 3456 pixels (12 million pixels). Downwelling zenith radiance varies substantially within single images and between successive images obtained at 4-s intervals. Variation in zenith radiance found on scales down to about 10 cm is attributed to variation in cloud optical depth (COD). Attention here is directed primarily to optically thin clouds, COD less than roughly 3. A radiation transfer model used to relate downwelling zenith radiance to COD and to relate the counts in the camera image to zenith radiance, permits determination of COD and cloud albedo on a pixel-by-pixel basis. COD for thin clouds determined in this way exhibits considerable variation, for example, an order of magnitude within the 40 m domain examined here and 50% over a distance of 1 m. An alternative to the widely used areal or temporal cloud fraction, denoted radiative cloud fraction, also evaluated on a pixel-by-pixel basis, is introduced. This highly data-intensive approach, which examines cloud structure on scales 3 to 5 orders of magnitude finer than satellite products, opens new avenues for examination of cloud structure and evolution.
-
C-AD Accelerator Physics Seminar
""Design Considerations for the 1.3GHz SRF Cavity for ARIEL at TRIUMF""
Presented by Dr. Philipp Kolb, BNL
Wednesday, June 15, 2016, 4 pm
Bldg. 911B - Large Conf. Rm. Rm A202"The Advanced Rare IsotopE Laboratory (ARIEL) at TRIUMF will triple the available rare isotope beam (RIB) time for experiments. The major part of ARIEL is the 50 MeV, high intensity cw eLINAC based on 1.3GHz SRF cavities. An eventual addition to the eLINAC is a recirculating beam line to allow FEL-ERL operation in addition to the RIB production beam. To avoid multipass beam break-up (BBU), the design of the SRF cavity had to be modified to reduce the shunt impedance of dipole higher order modes (HOM). Work on the cavity design and HOM load measurements will be shown as well as results of the vertical and horizontal cavity tests."
-
Condensed-Matter Physics & Materials Science Seminar
"Quantiative Determination of the the Fluctuations Leading to Superconductivity in Cuprates"
Presented by Chandra Varma, University of California, Riverside
Tuesday, June 14, 2016, 1:30 pm
ISB Bldg. 734, Conf. Rm. 201 (upstairs)Hosted by: 'Peter D. Johnson'
I will report on Laser based ARPES of unprecedented accuracy and stability (taken by the group of Xingjiang Zhou, IOP, Beijing), together with a method of analysis suggested by me (and carried out with the group of Han-Yong Choi, Asia Pacific Center for Theoretical Physics, Korea), to quantitatively extract the e↵ective frequency and momentum dependent interactions of fermions in both the full symmetry (normal) and the d-wave (pairing) symmetry in a family of cuprates. The results are remarkably simple. The principal interactions are of the form: I(k, k',w)~g0 [(1−cos(20k)cos(20'k)]F(w) They are separable functions of momentum and frequency, the first part is the repulsive part and the second part is the attractive d-wave part. F(w) is nearly constant with an upper-energy cutoff of about 0.4eV. The dimensionless coupling constant g0 ~ 0.15. These results were predicted in a theory of superconductivity and of the strange metal phase by quantum-critical fluctuation of loop-currents. They also rule out several alternatives proposed. I will also comment on the normal state and superconductivity in the Fe-based compounds.
-
Nuclear Physics Seminar
"Measurement of high-mass muon pairs from ultraperipheral lead-lead collisions with the ATLAS detector at the LHC"
Presented by Peter Steinberg, BNL
Tuesday, June 14, 2016, 11 am
Small Seminar Room, Bldg. 510Hosted by: 'Oleg Eyser'
Exclusive dimuon pairs with invariant mass Mμμ>10 GeV have been measured in ultra-peripheral lead-lead collisions at √sNN=5.02 TeV, using an integrated luminosity of 515 μb−1 taken with the ATLAS detector at the LHC in 2015. These very low-multiplicity interactions were recorded using an experimental trigger requiring a muon, low total transverse energy recorded in the calorimeter system, gaps at forward angles, and a reconstructed track. Events are selected to have no-other final state particles than a pair of opposite-sign dimuons. The cross section for dimuon pairs in Pb+Pb collisions is presented as a function of pair mass (Mμμ) and pair rapidity (Yμμ) and is well-described by calculations of Pb+Pb→Pb(*)+Pb(*)+μ+μ− using STARLIGHT 1.1 calculations. These data will improve the understanding of the strong electromagnetic fields surrounding the nucleus, which enable future UPC measurements utilizing these high energy probes.
-
Nuclear Seminar
"Generalizations of relativistic hydrodynamics"
Presented by Piotr Surowka, Harvard
Friday, June 3, 2016, 2 pm
Small Seminar Room, Bldg. 510Hosted by: 'Yi Yin'
Recent developments have shown that relativistic Landau and Lifshitz hydrodynamics does not possess the most general structure. It has to generalized to account for new phenomena. I will show how to do that in two directions. One will include parity-odd transport contributions connected to anomalies, the other will capture a dissipative fluid coupled to non-Abelian degrees of freedom such as color currents or spin currents. I will mention possible applications to quark-gluon plasma and condensed matter systems.
-
Nuclear Seminar
"Global Hyperon Polarization in Semicentral Heavy Ion Collisions Measured by STAR"
Presented by Mike Lisa, Ohio State University
Tuesday, May 31, 2016, 11 am
Small Seminar Room, Bldg. 510Hosted by: 'Oleg Eyser'
Non-central collisions between ultra-relativistic heavy ions involve thousands of h-bar of angular momentum. Some of this angular momentum may be transferred to the quark-gluon plasma through shear forces that generate a vortical substructure in the hydrodynamic flow field. Understanding this fundamental femtoscopic substructure may be crucial, as we move beyond boost-invariant scenarios and rely more on sophisticated three-dimensional viscous models of the plasma. The vortical nature of the system is expected to polarize the spins of hadrons that eventually emerge. Lambda and Anti-Lambda hyperons, which reveal their polarization through their decay topology, should be polarized similarly in the direction of the system's angular momentum. These same collisions are also characterized by dynamic magnetic fields with magnitude as large as 10^{14} Tesla. Magnetic effects have been the focus of intense study in recent years due to their relevance to the Chiral Magnetic Effect (CME) and other novel phenomena. A splitting between Lambda and Anti-Lambda polarization may signal a magnetic coupling and provide a quantitative estimate of the field strength at freeze out. Physically, this strength depends on the conductivity of the QGP. The STAR Collaboration has made the first observation of global hyperon polarization along the direction of the angular momentum in non-central Au+Au collisions at Beam Energy Scan energies. Our preliminary results indicate that the QGP created at RHIC is the highest-vorticity fluid ever created in the laboratory. A magnetic splitting is hinted at, but the improved statistics and resolution achievable with future runs are required to make a definitive measurement of the magnetic field.
-
RIKEN Lunch Seminar
"Lefschetz-thimble path integral for studying the sign problem and Silver Blaze phenomenon"
Presented by Yuya Tanizaki, RBRC
Thursday, May 26, 2016, 12:30 pm
Building 510, Room 2-160Hosted by: 'Hiroshi Ohki'
Recently, Picard-Lefschetz theory gets much attention in the context of the sign problem, because it enables us to study the system with the complex classical action nonperturbatively by employing the semiclassical analysis. In this seminar, after its brief introduction, I will apply it to the one-site Hubbard model. This model has a severe sign problem, which looks quite similar to that of the finite-density QCD at low temperatures. By solving this model using the Lefschetz-thimble path integral, we are trying to understand the structure of the sign problem of finite-density QCD. Especially, I give a qualitative picture (or speculation) about the early-onset problem of the baryon number density, called the baryon Silver Blaze problem. The complex Langevin method will also be discussed if time allows.
-
High Performance Computing and Programming Event
"OpenACC and GPU Hands-on workshop"
Presented by Presented by NVIDIA instructor Bob Crovella
Wednesday, May 25, 2016, 8:30 am
Stony Brook UniversityNVIDIA and the Institute for Advanced Computational Science (IACS) at Stony Brook University are pleased to be organizing a 2-day High Performance Computing and Programming event. Presented by NVIDIA instructor Bob Crovella, the workshop will introduce programming techniques using OpenACC and will include topics such as optimization and profiling methods for GPU programming.
-
Nuclear Physics Seminar
"Exploring the Neutron Spin Structure"
Presented by Matt Posik, Temple University
Tuesday, May 24, 2016, 11 am
Small Seminar Room, Bldg. 510Hosted by: 'Oleg Eyser'
Jefferson Lab experiment E06-014, performed in Hall A, made measurements of the double-spin asymmetries and absolute cross sections in both the DIS and resonance regions by scattering longitudinally polarized electrons at beam energies of 4.74 and 5.89 GeV from a longitudinally and transversely polarized 3He target. Through these measurements various aspects of the neutron spin structure were investigated. The g2 nucleon spin-dependent structure function contains information beyond the simple parton model description of the nucleon. It provides insight into quark-gluon correlations and a path to access the confining local color force a struck quark experiences just as it is hit by the virtual photon due to the remnant di-quark. The quantity d2, a measure of this local color force, has its information encoded in an x2 weighted integral of a linear combination of spin structure functions g1 and g2 and thus is dominated by the valence-quark region at large momentum fraction x. To date, theoretical calculations and experimental measurements of the neutron d2 differ by about two standard deviations. Therefore E06-014 made a precision measurement of this quantity. The polarized quark distributions were also investigated through measurements of the virtual photon-nucleon asymmetry A1^n, the structure function ratio g1/F1, and quark ratio (delta d+delta d_bar)/(d+d_bar). The E06-014 results for the spin structure functions (g1,g2) on 3He, dn2, An1, (delta d+delta d_bar)/(d+d_bar), and our extractions of the neutron color electric and magnetic forces will be presented.
-
High Performance Computing and Programming
"OpenACC and GPU Hands-on workshop"
Presented by Presented by NVIDIA instructor Bob Crovella
Tuesday, May 24, 2016, 8:30 am
Stony Brook UniversityNVIDIA and the Institute for Advanced Computational Science (IACS) at Stony Brook University are pleased to be organizing a 2-day High Performance Computing and Programming event. Presented by NVIDIA instructor Bob Crovella, the workshop will introduce programming techniques using OpenACC and will include topics such as optimization and profiling methods for GPU programming.
-
Nuclear Theory/RIKEN Seminar
"The jet quenching parameter q-hat, and its relation to the TMDPDF"
Presented by Abhijit Majumdar, Wayne State University
Friday, May 20, 2016, 2 pm
Small Seminar Room, Bldg. 510Hosted by: '''Soeren Schlichting'''
Based on prior work by the JET collaboration, the importance of the factorization and scale evolution of the jet quenching parameter q-hat will be outlined. This will turn out to be important for both phenomenological extractions of q-hat as well as for first principle determinations on the lattice. I will argue that for jets at RHIC and LHC, q-hat does not lie within the range of Bjoerken-x where small x effects would be considered to be dominant. Given this situation, q-hat will be found to be an integral over an operator product separated in both light-cone and transverse distance, but somewhat different from a ``traditional'' TMDPDF. This new distribution will be studied at Next-to-Leading Order and the fate of non-standard divergences discussed.
-
Particle Physics Seminar
"Searches for New Physics in boosted diboson topologies at ATLAS"
Presented by Carmacho Toro, University of Chicago
Thursday, May 19, 2016, 3 pm
Small Seminar Room, Bldg. 510Hosted by: 'Michael Begel'
The large increase in collision energy that the LHC reached in Run 2 provides an unprecedented opportunity to search for new physics beyond the Standard Model (SM). Various extensions of the SM predict the existence of heavy resonances at the TeV scale, which couple predominantly to the Higgs and electroweak gauge bosons. At high resonance masses the hadronic decay products of these energetic bosons tend to be highly collimated and the usual identification techniques fail to disentangle the decay products of our bosons. In this seminar I will describe the jet-substructure techniques explored by ATLAS analyses and present the results of the ATLAS searches using Run-2 data.
-
RIKEN Lunch Seminar
"Kosterlitz-Thouless transition and chiral rotation in external electromagnetic field"
Presented by Gaoqing Cao, Fudan University
Thursday, May 19, 2016, 12:30 pm
Building 510, Room 2-160Hosted by: ''Daniel Pitonyak''
In 2+1 dimensional system, the most important phase transition should be of the Kosterlitz-Thouless (KT) type. We determined the KT transition temperature T_KT as well as the mass melting temperature T^* as a function of the magnetic field. It is found that the pseudogap domain T_KT < T < T^* is enlarged with increasing strength of the magnetic field. The influence of a chiral imbalanceμ_5 was also studied. We found that even a constant axial chemical potential μ_5 can lead to inverse magnetic catalysis of the KT transition temperature in 2+1 dimensions. This is actually the de Haas—van Alphen oscillation. Furthermore, we studied the QCD vacuum structure under the influence of an electromagnetic field with a nonzero second Lorentz invariant I_2=E·B. We showed that the presence of I_2 can induce neutral pion (π_0) condensation in the QCD vacuum through the electromagnetic triangle anomaly. Within the frameworks of chiral perturbation theory at leading small-momenta expansion as well as the Nambu—Jona-Lasinio model at leading 1/Nc expansion, a universal dependence of the π_0 condensate on I_2 was found. The stability of the π_0-condensed vacuum is also discussed.
-
HET/RIKEN Seminar
"Higgs Pair Production in Extensions of the Standard Model"
Presented by Ramona Groeber, Roma Tre
Wednesday, May 18, 2016, 2 pm
Small Seminar Room, Bldg. 510Hosted by: 'Pier Paolo Giardino'
Higgs pair production is not only interesting as a probe of the trilinear Higgs self-coupling, but beyond the Standard Model physics can influence the Higgs pair production cross section in many different ways, for example by new couplings, new loop particles or new resonances. In this talk, I will address the question whether we could see for the first time deviations from the Standard Model in Higgs pair production assuming that no deviations were seen before. Furthermore, for certain models I will show how higher order corrections influence the cross section.
-
Condensed-Matter Physics & Materials Science Seminar
"Equilibrium States and Dynamics of Spin Assemblies in Magnetic Thin Films, Heterostructures and Nanostructured Entities"
Presented by Ramesh B. Budhani, Indian Institute of Technology Kanpur
Tuesday, May 17, 2016, 11 am
Building 480, Conference RoomHosted by: 'Lijun Wu'
The orientation of spin assemblies in ferromagnetic thin films and nanostructures can take a variety of shapes depending on the relative strength of factors contributing to their magnetic free energy. These factors are derived from the direct quantum mechanical exchange between the electronic spins or those mediated by impurities, and those associated with the size, shape, crystallographic structure, strain, dipolar interactions and external fields. Here we present three cases where the orientational dynamics has been studied as functions of temperature, magnetic field strength and the elapsed time after acquiring a particular configuration. These studies are based on magnetic force microscopy and bulk magnetometry measurements on strain epitaxial films of La0.67Ca0.33MnO3, and lithographically patterned submicron size ring assemblies of permalloy and Co/Pd multilayers, which also form artificial spin ices. Towards the end of this lecture we will discuss interface driven magnetic and electronic phenomena in magnetic thin films.
-
Condensed-Matter Physics & Materials Science Seminar
"Dirac Materials"
Presented by Alexander Balatsky, Los Alamos National Laboratory
Monday, May 16, 2016, 11 am
ISB Bldg. 734, Conf. Rm. 201 (upstairs)Hosted by: 'Peter D. Johnson'
Discoveries of superfluid phases in 3He, high Tc superconductors, graphene and topological insulators have brought into focus materials where quasiparticles are described by same Dirac equation that governs behavior of relativistic particles. I will discuss how this class of materials, called Dirac materials, exhibits unusual universal features seen in numerous realizations: Klein tunneling, chiral symmetries and impurity resonances. Goal of this talk is to explore these similarities and discuss the unique role of symmetries that protect Dirac spectrum and possible routes to generate gaps due to many body instabilities. We will also discuss ongoing investigation of the symmetries of Dirac materials, quantum imaging, and means to control their properties. At the end we will propose to use modern tools to design artificial Dirac Materials. One example would be the design Bosonic Dirac materials that host bosonic Dirac excitations, something that would not be possible in particle physics.
-
Nuclear Theory/RIKEN Seminar
"Evolution of the jet opening angle distribution in holographic plasma"
Presented by Andrei Sadofyev, MIT
Friday, May 13, 2016, 2 pm
Small Seminar Room, Bldg. 510Hosted by: ''Soeren Schlichting''
Energetic jets are particularly interesting probes of QGP created in heavy ion collisions. Recently a lot of progress was made in attempting to describe the jet evolution in holography. In this talk I'll present an application of a simple dual model to study the jet substructure starting with energy and angle distributions from pQCD. In particular I will show that there are two competing effects: (1) each individual jet widens as it propagates through plasma; (2) the final jet opening angle distribution becomes narrower since wider jets lose more energy and less likely to survive. So, the mean opening angle for jets with a given energy can easily shift toward smaller angles, even while every jet in the ensemble broadens.
-
Particle Physics Seminar
"Muon antineutrino oscillations at T2K"
Presented by Jordan Myslik, University of Victoria
Thursday, May 12, 2016, 3 pm
Small Seminar Room, Bldg. 510Hosted by: 'Xin Qian'
The T2K ("Tokai to Kamioka") experiment is a long-baseline neutrino oscillation experiment in Japan. A beam of muon neutrinos or muon antineutrinos is produced at the Japan Proton Accelerator Research Complex (J-PARC) in Tokai. The unoscillated neutrino flux is measured by the near detector complex 280 m from the proton target, and the oscillated neutrino flux is measured by the far detector, Super-Kamiokande, 295 km away. Using a beam of muon neutrinos, T2K has performed precise measurements of muon neutrino disappearance, and discovered muon neutrino to electron neutrino oscillation by measuring electron neutrino appearance. Since the summer of 2014, T2K has been taking data using a beam of muon antineutrinos, and has released the results of both a muon antineutrino disappearance analysis and an electron antineutrino appearance analysis, both using antineutrino beam data up to the summer of 2015. This talk will discuss these analyses, going into detail about the role played by the near detector, and looking at future directions.
-
RIKEN Lunch Seminar
"The Functional Renormalization Group Method and Delayed Magnetic Catalysis"
Presented by Stefan Rechenberger, University of Darmstadt
Thursday, May 12, 2016, 12:30 pm
Building 510, Room 2-160Hosted by: ''Daniel Pitonyak''
This talk will start with a very general introduction to the Functional Renormalization Group method, a powerful non-perturbative tool which can be applied to various problems. The second part of the talk will demonstrate this by discussing the influence of an external magnetic field on the chiral phase transition in the theory of strong interaction. The Functional Renormalization Group analysis shows that, driven by gluon dynamics, the chiral critical temperature decreases for small values of the magnetic field. For large values of the external field, however, the phase transition temperature increases.
-
HET/RIKEN Seminar
"Axions and Topology"
Presented by Simon Mages, Forschungszentrum Juelich
Wednesday, May 11, 2016, 2 pm
Small Seminar Room, Bldg. 510Hosted by: ''Tomomi Ishikawa''
This talk will be centered around the calculation of the high temperature topological susceptibility in QCD. It will provide some background on our motivation from cosmology and particle physics, which is the dependence of axion physics on non-perturbative QCD. I will show our recent results on the quenched high temperature topological susceptibility and discuss difficulties with this conventional approach, which render dynamical studies unfeasible. I will also present our new approach based on formulating QCD on a non-orientable manifold, which is a promising candidate to solve issues related to topological freezing and the divergence of autocorrelations when approaching the continuum limit.
-
Nuclear Theory/RIKEN seminar
"Fluid dynamics for the anisotropically expanding quark-gluon plasma"
Presented by Dennis Bazow, The Ohio State University
Friday, May 6, 2016, 2 pm
Small Seminar Room, Bldg. 510Hosted by: ''Soeren Schlichting''
Local momentum anisotropies become large in the early stages of the quark-gluon plasma created in relativistic heavy-ion collisions, due to the extreme difference in the longitudinal and transverse expansion rates. In such situations, fluid dynamics derived from an expansion around an isotropic local equilibrium state is bound to break down. Instead, we subsume the slowest nonhydrodynamic degree of freedom (associated with the deviation from momentum isotropy) at leading order defining a local anisoptropic quasi-equilibrium state, thereby treating the longitudinal/transverse pressure anisotropy nonperturbatively. Perturbative transport equations are then derived to deal with the remaining residual momentum anisotropies creating a complete transient effective theory called viscous anisotropic hydrodynamics. This approach has been shown to dramatically outperform viscous hydrodynamics in several simplified situations for which exact solutions exits but which share with realistic expansion scenarios the problem of large dissipative currents. We will discuss the present status of applying viscous anisotropic hydrodynamics to the phenomenological description of the quark-gluon plasma in realistic expansion scenarios.
-
Particle Physics Seminar
"Probing the Nature of Neutrinos with Double Beta Decay"
Presented by Liang Yang, University of Illinois at Urbana-Champaign
Thursday, May 5, 2016, 3 pm
Small Seminar Room, Bldg. 510Hosted by: 'Xin Qian'
Understanding fundamental properties of neutrinos is of compelling interest to the nuclear and particle physics community. The discovery of neutrino oscillations is one of our first hints of physics beyond the Standard Model. Searching for neutrinoless double decay can provide key insights into the neutrino mass generation mechanism and put stringent constraints on the absolute neutrino mass scale. Such a rare decay, if exists, would signify the Majorana nature of neutrinos and the non-conservation of lepton number. In the past decade, large ultra-low background liquid xenon detectors have emerged as a promising technology that can push the neutrinoless double beta decay search to unprecedented sensitivity. In this talk I will describe recent results and prospects of current generation experiment EXO-200, as well as the R&D program for future tonne scale detector nEXO.
-
RIKEN Lunch Seminar
"Vorticity in heavy-ion collisions and cold atoms"
Presented by Xu-Guang Huang, Fudan University
Thursday, May 5, 2016, 12:30 pm
Building 510, Room 2-160Hosted by: ''Daniel Pitonyak''
Vorticity describes the local rotation of the fluid. I will talk about our recent study of the event-by-event generation of flow vorticity in heavy-ion collisions. Several special properties of the vorticity in heavy-ion collisions will be discussed, e.g., the impact parameter dependence, the collision energy dependence, the spatial distribution, the event-by-event fluctuation of the magnitude and azimuthal direction. Vorticity can drive vector and axial current in chiral quark-gluon plasma via the chiral vortical effect. I will discuss the collective gapless mode, the chiral vortical wave, emerging from CVE and its experimental implications in heavy-ion collisions. Finally, I will consider the rotating trapped cold atomic gases and show that when there is a Weyl spin-orbit coupling such cold atomic gases provide a desktop simulator of the chiral magnetic effect and chiral separation effect.
-
Physics Colloquium
"eRHIC Machine Design"
Presented by Thomas Roser, BNL
Tuesday, May 3, 2016, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: 'Robert Pisarski'
With the addition of a 20 GeV polarized electron accelerator to the existing Brookhaven Relativistic Heavy Ion Collider (RHIC), the world?s only high energy heavy ion and polarized proton collider, a future eRHIC facility will be able to produce polarized electron-nucleon collisions at center-of-mass energies of up to 145 GeV and cover the whole science case as outlined in the Electron-Ion Collider White Paper and endorsed by the 2015 Nuclear Physics Long Range Plan with high luminosity. The presentation will describe the eRHIC design concepts and recent efforts to reduce the technical risks of the project.
-
High Tc Superconductor Seminar
"Cooper-like paring and energy gap induced by ion electronic polarizability"
Presented by Yizhak Yacoby, Racah Institute of Physics, Hebrew University, Israel
Monday, May 2, 2016, 1:30 pm
Bldg. 734, ISB Conference Room 201 (upstairs)Hosted by: ''Ron Pindak and Ivan Bozovic''
We propose a model of Cooper-like pairing induced by the large ion polarizabilities of O2- in Bismutates and Cuprates and As3- and Se2- in the iron pnictides*. We show that the electrical potential field induced by a charge carrier contains in its vicinity pockets of negative potential causing charge carriers to attract each other. Using this model we calculate the approximate pairing and gap energies showing they are compatible with the gap energies measured in high-Tc superconductors. Furthermore we show that the isotope effect, coherence length, and the gap energy dependence on doping are consistent with those observed in high-Tc systems. * Work done in collaboration with Yakov Girshberg
-
Nuclear Theory/RIKEN Seminar
"Going with the flow: sign problem, Lefschetz thimbles and beyond"
Presented by Gokce Basar, University of Maryland
Friday, April 29, 2016, 2 pm
Small Seminar Room, Bldg. 510Hosted by: '''Soeren Schlichting'''
Monte Carlo method, a robust way of studying field theories and many body systems, suffers from the sign problem when the action is complex. This includes an important set of problems such as most field theories, including QCD, and strong correlated electronic systems at finite density, as well as computation of real time quantities like transport coefficients. I will show that lifting the path integration to a complex manifold provides a way to ameliorate the sign problem, and introduce a new algorithm for carrying on such a computation. I will give some quantum mechanical examples with severe sign problems, including finite density of fermions and real time observables where Monte Carlo simulations can be profitably performed by this method. Finally I will discuss the 3+1d Bose gas with nonzero chemical potential.
-
Particle Physics Seminar
"Higgs' invisible branching fraction at the LHC"
Presented by Tae Min Hong, University of Pennsylvania
Thursday, April 28, 2016, 3 pm
Small Seminar Room, Bldg. 510Hosted by: 'Michael Begel'
Does the Higgs have a large invisible branching fraction? Two approaches are presented. The first is an indirect constraint of the invisible branching fraction using precision Higgs couplings measurements. The second is a direct search of invisible decays. In particular, I will discuss in detail two of ATLAS's results: the H -> WW in VBF, which is one of the strongest inputs for the couplings and the evidence for VBF Higgs production, and the H -> invisible in VBF, which gives the strongest direct limit. Comparisons with CMS's results are made.
-
RIKEN Lunch Seminar
"Solving QCD2"
Presented by Alexei Tsvelik, BNL
Thursday, April 28, 2016, 12:30 pm
Building 510, Room 2-160Hosted by: 'Daniel Pitonyak'
We study a (1+1)-dimensional version of the famous Nambu-Jona-Lasinio model of Quantum Chromodynamics (QCD2) both at zero and finite chemical potential. We use non- perturbative techniques (non-Abelian bosonization and Truncated Conformal Space Approach). At zero chemical potential we describe a formation of fermion three-quark (nucleons and ?-baryons) and boson (two-quark mesons, six-quark deuterons) bound states and also a formation of a topo- logically nontrivial phase. When the chemical potential exceeds the critical value, the model has a rich phase diagram which includes phases with density wave and superfluid quasi-long-range (QLR) order and also a phase of a baryon Tomonaga-Luttinger liquid (strange metal). The QLR order results as a condensation of scalar mesons (the density wave) or six-quark bound states (deuterons).
-
HET/RIKEN Seminar
"Heavy Higgs Resonance Dip"
Presented by Sunghoon Jung, SLAC
Wednesday, April 27, 2016, 2 pm
Small Seminar Room, Bldg. 510Hosted by: ''Cen Zhang''
We discuss overlooked resonance shapes of heavy Higgs bosons that arise from the resonance-continuum interference with a complex phase. They include pure resonance dips and nothingness. We derive conditions under which they are produced and we modify narrow width approximation suitable for them. We then discuss how MSSM heavy Higgs searches at the LHC can be challenged and changed.
-
Physics Colloquium
"Neutrino Physics and Mass from Cosmology"
Presented by Marilena Loverde, Stony Brook University
Tuesday, April 26, 2016, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: 'Robert Pisarski'
Cosmic background neutrinos are nearly as abundant as cosmic microwave background photons, but their mass, which determines the strength of their gravitational clustering, is unknown. Neutrino oscillation data gives a strict lower limit on neutrino mass, while cosmological datasets provide the most stringent upper limit. Even if the neutrino masses are the minimum required by oscillation data, their gravitational effects on structure formation will nevertheless be detectable in — and in fact required to explain — data within the next decade. I will discuss the physical effects of the cosmic neutrino background on structure formation and present a new signature that may be used to measure neutrino mass with large galaxy surveys.
-
Center for Functional Nanomaterials Seminar
"Disordered water phases from ambient to ultrahigh pressure"
Presented by Roberto Car, Princeton University
Tuesday, April 26, 2016, 11 am
CFN, Bldg. 735, 2nd Fl. Seminar RoomHosted by: 'Deyu Lu'
Center for Functional Nanomaterials Special Seminar Disordered water phases from ambient to ultrahigh pressure Roberto Car Princeton University Tuesday, April 26, 2016 11:00 a.m. CFN, Bldg. 735, 2nd floor Seminar Room The unusual properties of water, including the thermodynamic anomalies of the liquid, the existence of more than one amorphous ice form, and the abnormal mobilities of the water ions, derive from the tetrahedral network of hydrogen bonds that hold the molecules together. Under applied pressure the topology of the network changes but local tetrahedrality is preserved as the system explores a variety of different phases until at extreme pressure the molecules dissociate into ions and the hydrogen bonds collapse. Modern ab-initio simulations provide a unifying picture of these processes. In this talk, I will review recent progress in these studies stressing connections between theory, simulation, and experiment. Bio Roberto Car of Princeton University is Ralph W. Dornte professor for chemistry with a simultaneous appointment at the Material Sciences Institute of the university. He is a professor in the Theory Department, of the Fritz Haber Institute of the Max Planck Society. His research focus is theory and numerical simulation (classical and quantum) of condensed and molecular systems. He studied physics and attained a doctorate in 1971 in nuclear technology at the Politecnico di Milano. After being professor for physics at SISSA in Trieste (1984-1991), and at University of Geneva (1991-1999) he joined Princeton University in 1999. In 2007, a birthday symposium was held at ICTP. He received the Aneesur Rahman prize in computational physics. The Aneesur Rahman Prize is the highest honor given by the American Physical Society for work in computational physics.
-
C-AD Accelerator Physics Seminar
Presented by Malek Haj Tahar, BNL
Friday, April 22, 2016, 4 pm
Large Conference Room, Bldg. 911B, Rm. A202"The problem of nuclear waste continues to raise lots of concerns of whether the nuclear power should continue when the issue of how to deal with its waste has not yet been resolved. After reviewing the history of the nuclear waste problem in the United States of America and other countries, the question of how to remediate this problem is tackled and several options discussed. The focus is on the Accelerator Driven System option, a hybrid technique combining a particle accelerator with a subcritical core. The scope includes technical considerations from the proton accelerator and up to the reactor core."
-
Particle Physics Seminar
"New constraints on cosmic inflation from the Keck Array"
Presented by Chris Sheehy, University of Chicago
Thursday, April 21, 2016, 3 pm
Small Seminar Room, Bldg. 510Hosted by: 'Anze Slosar'
The Keck Array, part of the BICEP/Keck program of small aperture cosmic microwave background (CMB) telescopes, is currently taking data at the South Pole in Antarctica. The goal of the BICEP/Keck program is to detect the B-mode pattern in the CMB's polarized anisotropy that would be a signature of cosmic inflation, or, barring a detection, to set upper limits that rule out some of the most favored theoretical scenarios. Previous results from BICEP2 and the Keck Array that detected B-modes at high significance consisted of data taken only at 150 GHz, and which could therefore not conclusively distinguish between a cosmological vs. galactic origin for the signal. A subsequent joint analysis with the Planck satellite collaboration that invoked their comparatively noisy but multifrequency maps revealed a large component of the signal to be from polarized thermal emission of galactic dust. In this talk, I will present the results from the first year of observations with Keck's new 95 GHz receivers. These results set the most stringent limits on cosmic inflation to date and mark the point at which CMB polarization now constrains inflation better than any other data set.
-
RIKEN Lunch Seminar
"Color fluctuation phenomena in high energy hadron & photon-A collisions"
Presented by Mark Strikman, Penn State University
Thursday, April 21, 2016, 12:30 pm
Building 510, Room 2-160Hosted by: ''Daniel Pitonyak''
Compositeness of the bound states and the Lorentz slowing down of high energy interactions in QED and QCD lead to emergence of new coherent phenomena. We focus on the phenomena related to the fluctuations of the strength of interaction (color fluctuations phenomena). First we consider gross violations of the Glauber model for centrality dependence of production of the leading jets in pA scattering predicted earlier within QCD and recent evidence for this phenomenon from the studies of hard pA collisions at the LHC and dAu collisions at RHIC. Color fluctuations also explain a large suppression of the cross section of coherent vector meson photoproduction as compared to the Glauber model observed recently in the ultraperipheral collisions at LHC. We outline perspectives of future studies of the color fluctuation phenomenon in ultraperipheral heavy ion collisions at the LHC and electron - nucleus colliders.
-
Environmental & Climate Sciences Department Seminar
"Improved Tandem Measurement Techniques for Gas Phase Nanoparticle Analysis"
Presented by Vivek Rawat, University of Minnesota
Wednesday, April 20, 2016, 11 am
Conference Room, Bldg 815EHosted by: 'Jian Wang'
Non-spherical, chemically inhomogeneous nanoparticles are encountered in a number of natural and engineered environments, including combustion systems, reactors used in gas-phase materials synthesis, and in ambient air. To better characterize these complex nanoparticles, tandem measurement techniques are well suited, in which analytes are characterized by two orthogonal properties (e.g. size and mass). Tandem measurement techniques have been applied in a number of situations; however, there are still a considerable number of fundamental developments needed to advance these approaches. Specifically, new instrument combinations (with existing instruments) and appropriate data inversion routines need to be developed to determine combined two-dimensional mass-size distribution functions, pure mass distribution and for mobility-mass analysis for sub 2-nm clusters (ions). With this motivation, we first develop and apply a data inversion routine to determine the number based size-mass distribution function (two dimensional distribution) from tandem differential mobility analyzer-aerosol particle mass analyzer (DMA-APM) measurements, while correcting for multiple charging, instrument transfer functions and other system efficiencies. This two dimensional distribution can be used to calculate the number based size distribution or the mass based size distribution. We employ this technique to analyze various spherical and non-spherical nanoparticles and examine the validity of this approach by comparing the calculated size distribution functions and mass concentrations with direct measurements of these quantities. In a second study, we utilize a transversal modulation ion mobility spectrometer (TMIMS) coupled with a mass spectrometer (MS) to study vapor dopant induced mobility shifts of sub 2 nm ion clusters. Isopropanol vapor is introduced into the TMIMS, shifting the mobilities of ions to varying extents depending on ion surface chemistry, which provides an improved separa
-
Physics Colloquium
"The nature of the composite fermion in quantum Hall liquids"
Presented by Dam Thanh Son, University of Chicago
Tuesday, April 19, 2016, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: 'Robert Pisarski'
The quantum Hall liquids are some of the most nontrivial strongly interacting states of matter. Experiments have established the existence of the composite fermion as an effective degree of freedom of quantum Hall systems near half filling. A long-standing problem of existing theories of the composite fermion is the lack of particle-hole symmetry of the lowest Landau level. I will describe how the particle-hole symmetry took a central role in recent theoretical discussions of the fractional quantum Hall effect; in particular, how a recent synthesis, motivated by the physics of graphene and topological insulators, has lead to a new understanding of the low-energy quasiparticle of the half-filled Landau level. According to the new picture, the composite fermion is a Dirac particle, with a gauge but non-Chern-Simons interaction. Distinctive consequences of the new proposal are outlined.
-
Nuclear Theory/RIKEN seminar
"Vorticular fluid and Lambda Polarization in High-energy Heavy-ion Collisions"
Presented by Xin-Nian Wang, LBNL/CCNU
Friday, April 15, 2016, 2 pm
Small Seminar Room, Bldg. 510Hosted by: ''Soeren Schlichting''
The strongly coupled quark-gluon plasma created in high-energy heavy-ion collisions has rich vortical structures that are caused by global total orbital angular momentum and transverse evolution of longitudinal flow. Fermions (quarks in sQGP phase and baryons in the hadronic phase) in such a vorticular fluid are naturally polarized due to spin-orbital. I will discuss both local and global quark polarization and how one can use the lambda polarization in the final state to study the vortical structure and constrain the transport properties of sQGP.
-
Particle Physics Seminar
"Nuclear reactor antineutrinos, hard to detect but with a traceable lineage."
Presented by Alejandro Sonzogni, BNL
Thursday, April 14, 2016, 3 pm
Small Seminar Room, Bldg. 510Hosted by: 'Xin Qian'
The antineutrino spectrum from nuclear reactors can be calculated using the so-called "summation method", which requires precise knowledge of the fission yield and decay properties of the about 1000 radionuclides produced in a reactor following the fission of the actinide fuel. Alternatively, the antineutrino spectra can also be calculated using the "conversion method", which relies on precisely measured electron spectra. We have recently updated both decay and fission data that enabled us to a) identify the nuclides that contributes the most at different energy regions, b) derive a systematic of the IBD cross section integrated spectra as function of Z and A, similar to that of beta-delayed neutrons, c) asses if an excess of antineutrinos observed at around 5.5 MeV can be discerned using nuclear data.
-
Center for Functional Nanomaterials Seminar
"Sub-50 fs Photophysics and Photochemistry of Transition Metal Complexes and Polyhalomethanes"
Presented by Sergey Mikhailovich Matveev, Bowling Green State University
Monday, April 11, 2016, 1:30 pm
CFN, Bldg. 735, 1st floor conf. rm. AHosted by: 'Mircea Cotlet'
Lowest energy electronic excited states (LEES) in transition metal complexes are the states most relevant for practical photophysical and photochemical processes. We investigated relaxation dynamic of two systems – copper chloride dianion with strong Jahn-Teller effect and hexabromoiridate dianion with spin-spin coupling, utilizing 2000 nm near-IR femtosecond (100 fs) pump-probe spectroscopy. In both systems, the Franc- Condon excited states of the transition metal complexes undergo internal conversion to the ground electronic states, but with significantly different lifetimes (55 fs and 360 ps, respectively), despite the fact that the metal-centered states are separated by the same energy gap (~5000 wavenumbers) from the respective ground state. This difference is explained by presence of a conical intersection between the first excited electronic and the ground states in the Cu(II) system due to strong Jahn-Teller linear distortion whereas the involved potential energy surfaces for the Ir(IV) complex are nested directly one above another. Another project under consideration is the ultrafast mechanisms of polyhalomethanes on the example of diiodomethane. This molecule has a tractable number of degrees of freedom, and, therefore, has served in literature as a model system for bond dissociation processes in both gas and condensed phases. In this work we implemented the state-of-the-art ultrafast (~35 fs) transient absorption experiment (supported by the most accurate multireference quantum chemical methods) to understand the UV photodissociation mechanism of methylene iodide molecules. We discovered previously unsuspected photochemical pathway in the UV photochemistry of methylene iodide, in which electronically excited molecules, rather than simply dissociate, undergo direct ~50-fs isomerization through a conical intersection into isomeric species. Host: Mircea Cotlet
-
Particle Physics Seminar
"Dark Matter Search Results from PICO-2L"
Presented by Chanpreet Amole, Queen's University, SNOLAB
Thursday, April 7, 2016, 10 am
Small Seminar Room, Bldg. 510Hosted by: 'Xin Qian'
New data are reported from a second run of the 2-liter PICO-2L C3F8 bubble chamber with a total exposure of 129 kg-days at a thermodynamic threshold energy of 3.3 keV. These data show that measures taken to control particulate con-tamination in the superheated fluid resulted in the absence of the anomalous back-ground events observed in the first run of this bubble chamber. One single nuclear-recoil event was observed in the data, consistent both with the predicted background rate from neutrons and with the observed rate of unambiguous multiple-bubble neutron scattering events. The chamber exhibits the same excellent electron-recoil and alpha decay rejection as was previously reported. These data provide the most stringent direct detection constraints on WIMP- proton spin-dependent scattering to date for WIMP masses < 50 GeV/c2.
-
'Science on Tap'
"A Conversation With Paul Sorensen"
Presented by Paul Sorensen, Brookhaven Lab
Tuesday, April 5, 2016, 7 pm
Stony Brook Yacht ClubHosted by: ''Alan Alda Center for Communicating Science''
Paul Sorensen recreates the birth of the universe, smashing the nuclei of gold atoms together with such extreme violence that they melt into a cosmic soup that hasn't existed since the universe was a microsecond old. In conversation with Stony Brook University's journalism professor, Steven Reiner, Sorensen will bring to vivid life the epic endeavor to create in Brookhaven National Laboratory's atom smasher minute specks of the hottest matter ever made on Earth, and tell us what these fleeting fireballs may reveal about the origin of everything, including ourselves.
-
Physics Colloquium
"Hunting for WIMPs in Panda Land"
Presented by Xiangdong Ji, University of Maryland
Tuesday, April 5, 2016, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: ''''Robert Pisarski''''
Weakly interacting massive particles (WIMPs), with properties similar to those of a heavy neutrino, have been a leading candidate for the 27% dark matter in the Universe. Direct detection experiments by detecting the nuclear recoils from elastic scattering of WIMPs with atomic nuclei have made huge strides in the last decade, improving the sensitivity by some five orders of magnitude. In this talk, I will describe the results from an adventure of searching for WIMPs with the PandaX, currently the most sensitive running liquid xenon dark matter detector, in the world's deep underground lab in the high mountains, western China.
-
Nuclear Theory/RIKEN seminar
"Studying Nucleons in Soliton Models"
Presented by Song Shu, Stonybrook University
Friday, April 1, 2016, 2 pm
Small Seminar Room, Bldg. 510Hosted by: ''Soeren Schlichting''
Both chiral solitons and confined solitons are discussed at finite temperatures and densities in effective models. Based on the solitons the nucleon properties are studied in thermal medium. The nucleon mass in medium is carefully calculated. It is showed that the chiral solitons could even survive after the chiral phase transition, while confined solitons collapse after the system is deconfined.
-
Particle Physics Seminar
"Milicharge: A Proposal"
Presented by Ben Kaplan, New York University
Thursday, March 31, 2016, 3 pm
Small Seminar Room, Bldg. 510Hosted by: ''Michael Begel''
I will present the status of the MilliQan experiment, a milli-charged particle detector we propose to install at LHC P5. The experiment would be commissioned during the next LHC shutdown in a service tunnel ~30m above the CMS interaction point, behind ~15m of rock. I will present the theoretical motivation for building the detector, its proposed experimental design, and the expected sensitivity to milli-charged particles.
-
RIKEN Lunch Seminar
"Sphalerons Far From Equilibrium and Associated Phenomena"
Presented by Mark Mace, Stony Brook University
Thursday, March 31, 2016, 12:30 pm
Building 510 Room 2-160Hosted by: 'Daniel Pitonyak'
In this talk, I will present a first computation of sphalerons in the glasma; the highly occupied, weakly coupled gluon dominated pre-equilibrium matter created at early times after an ultra-relativistic heavy ion collisions. The sphaleron transition is a well known ingredient in the generation of anomalous vector current from a strong external magnetic field, the so-called Chiral Magnetic Effect. We perform classical-statistical real-time lattice simulations to study the dynamics of these topological transitions; simplifying our description by employing SU(2) gauge fields and neglecting the longitudinal expansion for this first study. I will show that the non-equilibrium sphaleron transition rate is time dependent and non-Markovian, in addition to being dominant in comparison to the thermal equilibrium sphaleron transition rate. In addition, we can measure the scaling and separation of physical scales in analogy to those from thermal equilibrium, in order to parameterize this rate and understand the approach to equilibrium. I will then demonstrate that it is the magnetic screening length, which we extract non-perturbatively, that controls this rate. Additionally, I will briefly mention studies of related anomalous transport effects that we plan on studying using this first principles classical-statistical real-time lattice technology.
-
Condensed-Matter Physics & Materials Science Seminar
"Topological Insulators and Dirac Semimetals - Recent Progress in New Materials"
Presented by Robert J. Cava, Princeton University
Thursday, March 31, 2016, 10 am
Large Seminar Room, Bldg. 510Hosted by: ''Peter D. Johnson''
"New materials give new properties" describes the goal of our solid state chemistry research program. This goal would be much easier to attain if there was a reliable way to predict the stability of an unknown non-molecular solid, then predict what its properties would be, then make it as a real material and then finally test it, but unfortunately that is not the case; establishing such a process is the grand challenge in contemporary solid state chemistry, and so we have to operate differently. Our discussions with experimental and theoretical physicists teach us about current issues in the electronic and magnetic properties of matter, and our chemistry background teaches us how to think about crystal structures and bonding; our work is about trying to put these two cultures together to find new materials. In this talk I will describe some of our recent results in Topological Insulators and Dirac and Weyl Semimetals.
-
Physics Colloquium
"Quark-Gluon Plasma: An Old and New Phase of Quantum Matter"
Presented by Jinfeng Liao, Indiana University
Tuesday, March 29, 2016, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Robert Pisarski
The use of fire was instrumental for human civilization. Early conception of varied phases of matter as well as transitions among them, perhaps developed from e.g. burning wood and heating water. Those ancient pursuits continue into the modern quest for understanding the structure of matter under extreme conditions: what's the phase of matter when heated to unprecedented temperature? The answer to this question relies upon our understanding of the strong nuclear force, which is described by quantum chromodynamics (QCD). First principle calculations of QCD predict that the normal nuclear matter, when heated to be hot enough, will change into a new phase of matter called the quark-gluon plasma (QGP). In fact, the QGP was an old phase of matter that occupied the early universe shortly after the Big Bang. Today, such primordial droplets of QGP can be re-created repeatedly and measured precisely in relativistic heavy ion collisions (often called the Little Bangs). Remarkable discoveries have been made at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC) that together reveal the QGP as a nearly perfect quantum liquid with superior opaqueness. We will discuss a number of novel properties of QGP. In particular we will highlight the recent progress on how certain unusual transport phenomena stemming from microscopic chiral anomaly, which is intrinsically quantum mechanical, could manifest themselves in the macroscopic QGP fluid. A very brief survey will be given on the theoretical developments, the experimental search in heavy ion collisions, as well as the recent exciting progress of such physics in Dirac and Weyl semimetals.
-
Condensed-Matter Physics & Materials Science Seminar
"Phase transitions in strongly correlated systems from diagrammatic multi-scale methods"
Presented by Andrey Antipov, University of Michigan
Thursday, March 24, 2016, 1:30 pm
Bldg. 734, ISB Conf. Rm. 201 (upstairs)Hosted by: ''Alexei Tsvelik''
The dynamical mean field theory (DMFT) has become the standard tool in describing strongly correlated electron materials. While it captures the quantum dynamics of local fields, it neglects spatial correlations. To describe e.g. anti-ferromagnetism, unconventional superconductivity or frustration a proper treatment of non-local correlations is necessary. Diagrammatic multi-scale approaches offer an elegant option to accomplish this: the difficult correlated part of the system is solved using a non-perturbative many-body method, whereas 'easier', 'weakly correlated' parts of the problem are tackled using a secondary perturbative scheme. Here we employ such a method, the dual fermion approach, to problems of charge and spin ordering in Falicov-Kimball and Hubbard models by constructing a systematic diagrammatic extension on top of DMFT. Near the critical point model we study the interplay between charge and spin excitations and long-range fluctuations. We show that such multi-scale approach is indeed capable of capturing the non mean-field nature of the critical point of the lattice model and correctly describes the transition to mean-field like behavior as the number of spatial dimensions increases. Our numerical method is available as a freely distributed open-source code.
-
Special RIKEN/HET Seminar
"Axion Phenomenology from Unquenched Lattice QCD"
Presented by Guido Martinelli, Rome University
Thursday, March 24, 2016, 11 am
Large Seminar Room, Bldg. 510Hosted by: '''Hiroshi Oki'''
We investigate the topological properties of Nf = 2 + 1 QCD with physical quark masses, both at zero and finite temperature. At zero temperature both finite size and finite cut-off effects have been studied by comparing the continuum extrapolated results for the topological susceptibility χ with the predictions from chiral perturbation theory. At finite temperature, we explore a region going from Tc up to around 4Tc, where continuum extrapolated results for the topological susceptibility and for the fourth moment of the topological charge distribution are obtained. While the fourth moment converges to the dilute instanton gas prediction the topological susceptibility differs strongly both in the size and in the temperature dependence. This results in a shift of the axion dark matter window of almost one order of magnitude with respect to the instanton computation.
-
Physics Colloquium
"Flavor Physics for Non Experts : (A Theory) Overview"
Presented by Guido Martinelli, Rome University
Tuesday, March 22, 2016, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Robert Pisarski
The status of the Unitarity Triangle including the most recent results from LHC, will be presented. Different possibilities for detecting, in the quark sector, signals of physics beyond the Standard Model will be considered. The conclusion is that, even allowing for general New Physics loop contributions, the generalized Unitarity Triangle must be very close to the Standard Model one. Together with direct searches of new particles at LHC, this result strongly constraints models of New Physics.
-
Condensed-Matter Physics & Materials Science Seminar
"SU(N) symmetric tensor network simulations of strongly correlated quantum many-body systems"
Presented by Andreas Weichselbaum, Ludwig Maximilians University
Tuesday, March 22, 2016, 1:30 pm
Small Seminar Room, Bldg. 510Hosted by: ''Alexei Tsvelik''
Tensor network simulations have emerged as a powerful algebraic framework for the simulation of strongly correlated quantum many-body systems. Their great appeal lies in the fact that they are exact in that they do no rely on small parameters. They significantly extend exact diagonalization to much larger system sizes in (effective) 1D or 2D all the way to the thermodynamic limit. I will give a brief introduction based on the hugely successful methods such as the numerical renormalization group (NRG) or the density matrix renormalization group (DMRG) with focus on multi-orbital systems, both symmetric and non-symmetric. A versatile numerical tool in that respect is my recently developed tensor library QSpace that can efficiently deal with generic symmetry settings including SU(N). After a brief motivation via the prototypical symmetric multi-orbital system of iron impurities in gold or silver, I will present recent results on a dynamical mean-field theory (DMFT) study concerning the coherent-incoherent crossover in iron-pnictides, followed by recent work on the spin-1 Heisenberg kagome lattice and preliminary results on SU(N) spin ladders.
-
Condensed-Matter Physics & Materials Science Seminar
"From Molecular Beam Epitaxy to high magnetic field Quantum Oscillations"
Presented by Yoshiharu Krockenberger, NTT Basic Research Laboratories
Monday, March 21, 2016, 1:30 pm
Bldg.480 Conf. RmHosted by: 'Ivan Bozovic'
Cuprate superconductors present a major challenge in condensed matter physics not only due to their electron correlations but also due to their complex crystal structure. Complex crystal structures, i.e. various cations at various lattice positions, demand for the utmost caretaking when synthesizing them. In particular, Molecular Beam Epitaxy is the foremost versatile tool and technique that allows for the synthesis of such materials without the necessity to compromise on impurity phases. First, I introduce our custom designed Molecular Beam Epitaxy equipment which is empowered by e-guns, not effusion cells, and controlled by electron impact emission spectroscopy. After presenting several material systems I present high magnetic field quantum oscillation data on films synthesized by our Molecular Beam Epitaxy systems.
-
Nuclear Theory/RIKEN Seminar
"Duality, Dimensions and Reduction on the Lattice"
Presented by Joel Giedt, Rensselaer Polytechnic Institute
Friday, March 18, 2016, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Soeren Schlichting
Montonen and Olive found evidence that a duality could exist in Yang-Mills with adjoint scalars. In this scheme, the 't Hooft-Polyakov monopole forms a gauge triplet with the photon, leading to a theory equivalent to the Georgi-Glashow model but with magnetic charge replacing electric charge. The duality is believed to be realized in N=4 super-Yang-Mills. We are pursuing numerical, nonperturbative evidence for this S-duality using our lattice formulation. Two lines of approach are being taken, which I will discuss. First, we attempt to show that there is a value of the gauge coupling for which the W boson mass is equal to the monopole mass. Second, we are relating the 't Hooft loop to the Wilson loop at this self-dual coupling. On a somewhat unrelated topic, we also discuss the determination of anomalous dimensions on the lattice. In the dual gravitational picture these correspond to masses of fields in the bulk, so that some aspects of the gauge-gravity duality could be tested by such determinations. In particular in N=4 super-Yang-Mills there are predictions for the dimensions of non-protected operators at the self-dual point, based on the superconformal bootstrap.
-
Physics Colloquium
"Hot-dense Lattice QCD: Supercomputing Extreme Matter"
Presented by Swagato Mukherjee, BNL
Tuesday, March 15, 2016, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: 'Rob Pisarski'
I will discuss the role of supercomputing in revealing the phases and properties of the hot-dense quark-gluon matter created during relativistic heavy-ion collisions. I will present a brief overview of the recent achievements of ab-initio lattice Quantum Chromodynamiecs computations at non-zero temperatures and densities.
-
Condensed-Matter Physics & Materials Science Seminar
"Real-space Visualization of the Superconducting Proximity effect and Josephson tunneling on Nano-sized Pb thin film"
Presented by Howon Kim, Institute for Solid State Physics, University of Tokyo, Japan
Wednesday, March 9, 2016, 11 am
ISB Bldg. 734 Conf. Rm. 201 (upstairs)Hosted by: Kazuhiro Fujita
The proximity and Josephson effects are well-known phenomenon and widely used terms in superconductivity. Due to the recent advances in fabrication techniques those phenomenon has been extensively studied to give a new insight to the superconductor-based device applications. Nevertheless, many of these works addressed macroscopic properties of the samples, and thus local information is still missing. In this talk, I will discuss how we can realize the proximity effect and Josephson effect using scanning tunneling microscope at a nanometer scale. In the first part of the talk, we address how the local surface structure can influence on the proximity effect at the interface between superconducting two-dimensional Pb islands and a single-atomic-layer metal by performing local tunneling spectroscopy. From the spectroscopic mapping taken around the Pb-based S/N interface, we observed the gap at the Fermi energy, reminiscent of the superconducting gap, propagating into the metal region (proximity effect) and its depth decaying with the distance from the interface. Additionally, we observed that the propagation of the gap is terminated by the steps of the substrate and enhancement of the gap-depth in the area between the interface and the step edge. The experimental results are compared with the results of quasi-classical theory based on the Usadel equation. [1] The second part of the talk addresses atomic-scale S-S junctions by using scanning tunneling microscopy and spectroscopy. In our local conductance measurements between superconducting Pb islands on Si(111) or Ge(111) and Pb layers on the end of PtIr tip apex, we observed evolution of not only the normal-state conductance [2] but also a zero-bias peak (ZBP) from tunnel to atomic contact, which corresponds to the Josephson current, with a decrease in the tip-substrate distance on the different atomic sites on the surface crystalline lattice of the substrate. With a help of multiple Andreev reflectio
-
Environmental & Climate Sciences Department Seminar
"Plant respiration: lessons from high latitudes for ecosystem carbon balance modelling"
Presented by Paul P. Gauthier, Princeton University
Wednesday, March 9, 2016, 11 am
John Dunn Seminar Room, Bldg. 463Hosted by: Alistair Rogers
Climate-mediated changes in ecosystem C balance are accepted as an important component of the biosphere response to climate change. Plant respiration and photosynthesis are major drivers of this balance but our lack of understanding of the controls and constrains surrounding their interaction stalls our capacity to predict future ecosystem changes. Using a new O2 isotopes method for measuring leaf functional traits, I will present a new approach to estimate the rate of leaf respiration in the light and its biochemical origin in temperate and arctic plants. The role of plant respiration as a key player for plant adaptation will also be discussed in the context of plant respiration modelling.
-
RIKEN Lunch Seminar
"Investigation of anomalous dynamics and the Chiral Magnetic Effect far from equilibrium"
Presented by Niklas Mueller, University of Heidelberg
Thursday, March 3, 2016, 12:30 pm
Building 510, Room 2-160Hosted by: Daniel Pitonyak
We investigate the impact of the Adler-Bell-Jackiw axial anomaly on the real-time dynamics of gauge theories in the strong field regime. By studying and comparing Abelian gauge theories, such as QED, with non-Abelian systems, we try to clarify the role of topological properties and initial conditions relevant far from equilibrium. We show that the Abelian version of the Chiral Magnetic Effect, which has been predicted in the context of ultra-relativistic heavy ion collisions, can result in non-trivial experimental signatures, which could possibly be observed in future high-intensity laser experiments. Further I will report on recent investigations of chiral production mechanisms in strong non-Abelian gauge fields and I will discuss the influence of topological objects such as sphalerons, far from equilibrium. Moreover I will show first results of the studies we have undertaken since my arrival here at BNL and discuss how the combination of these studies might be used to shed more light on the role played by anomalies in the early stages of a heavy ion collision.
-
Physics Colloquium
"Detection of Gravitational Waves and the First Observation of a Binary Black Hole Merger"
Presented by Imre Bartos, Columbia University
Tuesday, March 1, 2016, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Peter Petreczky
On September 14th 2015 the gravitational wave signature of a binary black hole merger was detected by the LIGO observatories. This marks the beginning of a completely new era of modern physics, the dawn of gravitational-wave astrophysics. We will discuss the discovery, its impact and its consequences.
-
Nuclear Physics Seminar
"Beam Energy Dependence of the Third Harmonic of Azimuthal Correlations in Au+Au Collisions at RHIC"
Presented by Paul Sorensen, BNL
Tuesday, March 1, 2016, 11 am
Small Seminar Room, Bldg. 510Hosted by: Oleg Eyser
I will present results from a harmonic decomposition of two-particle azimuthal correlations measured with the STAR detector in Au+Au collisions for energies ranging from 7.7 GeV to 200 GeV. v3 is studied as a function of the pseudorapidity di erence between particle pairs. Non-zero v3 is directly related to the previously observed large- narrow- ridge correlations and has been shown in models to be sensitive to the existence of a low viscosity Quark Gluon Plasma (QGP) phase. For sufficiently central collisions, v3 persist down to an energy of 7.7 GeV suggesting that QGP may be created even in these low energy collisions. In peripheral collisions at these low energies however, v3 is consistent with zero. When scaled by pseudorapidity density of charged particle multiplicity per participating nucleon pair, v3^2 for central collisions shows a minimum near 20 GeV.
-
Particle Physics Seminar
"Observation of Gravitational Waves from a Binary Black Hole Merger by LIGO"
Presented by Sergey Klimenko, University of Florida
Monday, February 29, 2016, 3 pm
Large Seminar Room, Bldg. 510Hosted by: Erin Sheldon
On September 14, 2015 at 09:50:45 UTC the Laser Interferometer Gravitational-wave Observatory (LIGO) Hanford, WA, and Livingston, LA, observatories detected a strong coincident signal. The signal matches the waveform predicted by general relativity for the inspiral merger of a pair of black holes and the ringdown of the resulting single black hole. A century after the fundamental predictions of Einstein and Schwarzschild, the gravitational waves are captured. I will present the details of this observation and discuss the results.
-
Nuclear Theory/RIKEN Seminar
"Real time method of thermal field theory"
Presented by Samir Mallik, Saha Institute of Nuclear Physics
Friday, February 26, 2016, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Soeren Schlichting
I review the basic ideas of real time formulation of thermal field theory. Then I like to consider the following topics in this formulation: 1) thermal propagator for a scalar field 2) spectral representation of two-point functions for arbitrary fields 3) perturbation expansion 4) one-loop self -energy 5) dilepton production
-
Particle Physics Seminar
"Project 8: tritium decays, neutrino masses, and single-electron spectroscopy"
Presented by Prof. Ben Monreal, UC Santa Barbara
Friday, February 26, 2016, 10 am
Small Seminar Room, Bldg. 510Hosted by: Xin Qian
Beta decay kinematics are, in principle, sensitive to the absolute values of the neutrino masses. Many decades of work with tritium decay have shown m_nu to be in the range 0—2.0 eV; require improvement in spectrometer resolution, statistics, and systematics. The KATRIN experiment will push the limits of classical techniques to reach 0.2 eV sensitivity. The Project 8 is developing what we hope is the next step in beta electron spectroscopy; we can now perform precise electron energy measurements, in-situ in a low-pressure gaseous source, by cyclotron radiation energy spectroscopy (CRES). I will show recent results from the Project 8 prototype, including the first CRES measurements in krypton, and our path to first molecular tritum measurements and to a future large atomic tritium experiment.
-
Particle Physics Seminar
"Giant detectors in solution-mined salt caverns"
Presented by Prof. Ben Monreal, UC Santa Barbara
Thursday, February 25, 2016, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Xin Qian
Many of particle physics' most interesting observables (neutrinos, dark matter, proton decay) require detectors installed underground. In many cases, the constraints associated with mines—-limited roof spans, limited sites, safety, and excavation costs—- are beginning to limit the scope of our experiments. The energy and chemical industries have 100 years of experience with a different type of underground space: solution-mined salt caverns. These are obtained by drilling into large salt formations and dissolving the salt with water. The caverns obtained can be enormous, deep, stable and above all inexpensive—-but of course they have their own access and pressure constraints. In this talk, I will argue that a wide range of desirable detector technologies, including giant gas TPCs, might be deployed with these caverns. In particular, I will talk about an (untested) TPC gas mixture I devised with these caverns in mind, but which may prove useful in conventional labs too.
-
RIKEN Lunch Seminar
"Lambda_c - N interaction from lattice QCD"
Presented by Takaya Miyamoto, Yukawa Institute for Theoretical Physics, Kyoto University
Thursday, February 25, 2016, 12:30 pm
Building 510 Room 2-160Hosted by: Hiroshi Oki
Recently, a new approach to investigate hadron interactions in lattice QCD has been proposed[1] and developed extensively by the HAL QCD Collaboration[2]. This method can be easily applied to heavy baryon systems even though it is difficult to obtain experimental data of heavy baryons. We have investigated the interaction between Lambda_c and nucleon (N) from lattice QCD using the HAL QCD method. This is the first step to understand charmed-baryon interaction in lattice QCD. In this talk, we present the current status of our research project onLambda_c-N interactions as well as future prospects. This talk is based on PoS (LATTICE 2015) 090.
-
Nuclear Theory/RIKEN Seminar
"Lattice QCD investigations of quark transverse momentum in hadrons"
Presented by Michael Engelhardt, New Mexico State University
Friday, February 19, 2016, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Soeren Schlichting
An ongoing program of evaluating transverse momentum dependent parton distributions (TMDs) within lattice QCD is reviewed, summarizing recent progress with respect to several challenges faced by such calculations. These lattice calculations are based on a definition of TMDs through hadronic matrix elements of quark bilocal operators containing staple-shaped gauge connections. A parametrization of the matrix elements in terms of invariant amplitudes serves to cast them in the Lorentz frame preferred for a lattice calculation. Results presented include data on the naively T-odd Sivers and Boer-Mulders effects, as well as the transversity and a worm-gear distribution. Correlating quark transverse momentum with impact parameter, one can extract quark orbital angular momentum directly,including both the Ji as well as the Jaffe-Manohar definitions.
-
Nuclear/Riken Theory Seminar
"The Transverse Structure of the Nucleon"
Presented by Marc Schlegel, University of Tuebingen
Friday, February 19, 2016, 11 am
Small Seminar Room, Bldg. 510Hosted by: Soeren Schlichting
Perturbative QCD based on the Parton Model of the nucleon is a very successful theoretical approach to describe high-energy processes at particle accelerators and colliders. In particular, parton distribution functions are key ingredients of this approach and give information on the partonic substructure of the nucleon. As such they deliver a one-dimensional picture of how the parton momenta are distributed in the nucleon. In this talk extensions of the parton model are presented which provide access to more detailed information on the dynamics of partons in the nucleon. In particular observables involving transversely polarized nucleons are discussed. They can be described in terms of dynamical quark-gluon correlations which in turn can be studied at an Electron-Ion Collider. Another extension of the parton model takes into account the intrinsic transverse motion of the partons. In this approach - called Transverse Momentum Dependent (TMD) factorization - one can study three-dimensional distributions of the parton momenta. In addition, implications of the transverse motion of gluons in the nucleon will be discussed for LHC physics.
-
Particle Physics Seminar
"Weighing the Giants: Anchoring Cluster Cosmology"
Presented by Adam Mantz, SLAC National Accelerator Laboratory
Thursday, February 18, 2016, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Erin Sheldon
The gas mass fractions and the distribution in mass and redshift of the galaxy cluster population provide powerful probes of cosmology, constraining the cosmic matter density, the amplitude of the matter power spectrum, properties of dark energy, and the mass of neutrinos, among other parameters. Historically, these tests have been limited by the absolute accuracy of cluster mass determinations. Here, mass measurements from weak lensing have an advantage over estimates based on observations of the intracluster medium (ICM), because the former are nearly unbiased and can be straightforwardly tested against simulations. I will describe recent cosmological constraints obtained from an analysis of X-ray selected cluster samples, incorporating extensive gravitational lensing data from the Weighing the Giants project — the first cluster cosmology study to consistently integrate a lensing mass calibration, including a rigorous quantification of all systematic uncertainties. The results highlight the power and potential of galaxy clusters, which constrain both the expansion of the Universe and the growth of cosmic structure, and their complementarity with other probes such as type Ia supernovae, large-scale galaxy surveys, and the cosmic microwave background.
-
Physics Colloquium
"Physics opportunities at future circular colliders"
Presented by LianTao Wang, University of Chicago
Tuesday, February 16, 2016, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Robert Pisarski
Following the discovery of the Higgs boson, there has been a lot discussion about the next step in high energy physics. Among different options, a couple of newly proposed next generation circular colliders, including FCC at CERN and CEPC/SPPC in China, have attracted a lot of attention. Through preliminary studies in the past couple of years, an exciting picture of their physics capabilities has emerged. In this talk, I will give an overview on this topic, focusing on some of the most important questions in high energy physics they can help addressing
-
Nuclear Physics Seminar
"Precision Jet Physics to Probe Strong Dynamics"
Presented by Dr. Daekyoung Kang, Los Alamos National Laboratory
Tuesday, February 16, 2016, 11 am
Small Seminar Room, Bldg. 510Hosted by: Oleg Eyser
Jets produced in the high energy collision of quarks and gluons at colliders are bunches of collimated particles traveling along the same direction. Jet productions are extensively studied in various colliders in search for new physics beyond the standard model and as a probe of new state of matter like QGP. In this talk, I will discuss jet study at a high precision as a new tool to probe strong dynamics in electron-proton collider. As an example, I will show the new tool can be used to determine the strong coupling constant and to improve our understanding of nuclear structure such as a parton distribution function of proton. With new level of precision not previously available for jets, the jet physics will provide one of milestones at the early stage of future Electron-Ion collider.
-
Nuclear Theory/RIKEN Seminar
"Understanding the structure of hadrons through spin observables in hard-scattering processes"
Presented by Daniel Pitonyak, BNL
Friday, February 12, 2016, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Soeren Schlichting
Almost all of the visible matter in the universe is built from hadrons, which are composed of quarks and gluons. One of the main challenges in nuclear physics is to understand this complex internal structure. In this talk, I will discuss how hard-scattering processes that involve the spin of hadrons give us insight into aspects of their inner-workings that otherwise would be inaccessible. I will focus on phenomena that arise when hadrons carry spin transverse to their direction of motion, which allow us to examine them in 3D and analyze correlations between their quarks and gluons. I will also consider a new attempt to resolve the so-called "spin crisis" of how the proton gets its spin by looking at how much spin can be carried by small-x quarks and gluons.
-
Condensed-Matter Physics & Materials Science Seminar
"Berezinskii-Kosterlitz-Thouless-like transition in a highly underdoped La2-xSrxCuO4"
Presented by Dragana Popovic, NHMFL Tallahassee
Thursday, February 11, 2016, 1:30 pm
Bldg. 734, ISB Conf. Rm. 201 (upstairs)Hosted by: Cedomir Petrovic
In two-dimensional superconductors, the transition to the metallic state takes place via thermal unbinding of vortex-antivortex pairs, as described by the Berezinskii-Kosterlitz-Thouless (BKT) theory. The occurrence of the BKT transition in bulk underdoped samples of cuprate superconductors, which are highly anisotropic, layered materials, has been controversial. Therefore, the nature of the superconducting transition in highly underdoped thick films of La2-xSrxCuO4 has been investigated using the in-plane transport measurements. Both the temperature dependence of the paraconductivity above the transition and the nonlinear current-voltage (I-V) characteristics across it exhibit the main signatures of the BKT transition. Moreover, the quantitative comparison of the superfluid stiffness, extracted from the I-V data, with the renormalization-group results for the BKT theory, reveals a large value of the vortex-core energy, strongly suggesting that the relevant length scale controlling the BKT-like transition in this layered material involves a few coupled layers. Finally, measurements of the fluctuations of the resistance with time (i.e. noise) provide evidence for the critical slowing down of the dynamics and the onset of correlated behavior. The details of the observed dynamical critical behavior of the BKT transition and the role of disorder will be discussed.
-
Center for Functional Nanomaterials Seminar
"In situ studies of nucleation and growth of nanoparticles under realistic conditions"
Presented by Elena Schevchenko, Argonne National Laboratory
Monday, February 8, 2016, 11 am
Conference Room A, Bldg. 735Hosted by: Oleg Gang
The progress in colloidal synthesis allowed reaching a high degree of controls in synthesis of nanoparticles. As a result, nanoparticles come in many different shapes, sizes and compositions. Combining multiple components within individual nanoparticles or doping of nanoparticles are simple ways to control chemical and physical properties at nanoscale to obtain efficient catalysts and advanced energy conversion and storage systems. However the successful synthetic protocols are based on empirical rules based on numerous trials and errors and often the mechanism of nucleation and growth of nanoparticles remains unclear. I will present in situ study on the nucleation and growth kinetics and the temporal changes in the crystal structure of the metal dumbbell NPs (e.g. CoPt3/Au, Pt/Au and PtFe/Au). Using synchrotron small- and wide-angle X-ray scattering (SAXS/WAXS) techniques we were able to catch the transient stages of structural and volumetric changes of NPs. We found that in the early stage of the reaction intermediate core/shell heterostructure is formed prior to dumbbells. The transition of the core/shell into the dumbbell occurs via strain relaxation of the pseudomorphic Au shell resulting in the nucleation of a strain-free Au domain. I will discuss the formation and doping process of iron and iron oxide NPs in real time by in situ synchrotron X-ray absorption spectroscopy. In our study we revealed that the mass flow of the metal triggered by oxidation is responsible for the internalization of the dopant (molybdenum) adsorbed at the surface of the host iron NPs. The new oxidation induced doping mechanism allows control over the doping levels by varying the amount of dopant precursor. Our in situ studies also showed that the dopant precursor substantially changes the reaction kinetics of formation of iron and iron oxide NPs.
-
RIKEN Lunch Seminar
"Kinetic regime of hydrodynamic fluctuations"
Presented by Yukinao Akamatsu, Stony Brook University
Thursday, February 4, 2016, 12:30 pm
Building 510 Room 2-160Hosted by: Hiroshi Ohki
Hydrodynamics is an effective theory of systems close to equilibrium. It has been applied to description of fireballs created in the heavy-ion collisions. With growing interests in fluctuation of observables, theoretical identification of its origin is crucial. One of such origins is thermal fluctuation required by the fluctuation-dissipation theorem. In this talk, I will present a new insight into the thermal fluctuation of hydrodynamics by separating the hard and soft scales in a given background. As an illustration, we adopt the Bjorken expansion as a background. The kinetic description of hard modes allows us simple interpretation of renormalization, long-time tails, and fractional powers of derivative expansion.
-
Physics Colloquium
"The New Big Science: the Changing Research Ecology at US Materials Science Facilities"
Presented by Robert Crease, Stony Brook University and, Catherine Westfall, Michigan State University
Tuesday, February 2, 2016, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Robert Pisarski
"We talk about a phase shift that has taken place over the past few decades at US national labs, in which large-scale materials science accelerators rather than high-energy physics accelerators became marquee projects at most major basic research laboratories in the post-Cold War era, accompanied by important changes in the character and culture of the research ecosystem at these laboratories. We consider some features, periodization, funding, and challenges of this phase shift, known as the "New Big Science."
-
Nuclear Theory/RIKEN Seminar
"New aspects of QCD dynamics at high density: Jet evolution in the QGP and wave turbulence""
Presented by Yacine Mehtar-Tani, INT Seattle
Friday, January 29, 2016, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Soeren Schlichting
An essential feature of the parton shower that form a jet evolving in vacuum is color coherence that suppresses large angle soft gluon radiation and thus, ensuing the collimation of the jet. In the presence of dense QCD matter jet constituents suffer a rapid color randomization and thus an alteration of color coherence: as a result a medium-induced gluon cascade, that can be described by a classical Makovian process, develop at large angles with respect to the jet axis [3]. A remarkable phenomenon emerges from such a cascade: the energy spectrum (of jet constituents) exhibits a scaling behavior, akin to wave turbulence, characterized by a constant flow of energy from the forward energetic patrons towards low momentum gluons down to the temperature of the plasma where energy is dissipated [4]. This picture is in agreement with a recent CMS analysis of missing energy in asymmetric dijet events where the energy balance is recovered at large angles and very soft particles [5]. In the second part of the talk I will discuss radiative corrections to jet observables that were shown to exhibit large double logarithmic enhancements. Owing to a large separation of time scales we have shown that these large corrections can be reabsorbed in a renormalization of the jet-quenching parameter q^, preserving the probabilistic picture of the parton cascade [6]. This result leads us to question the standard viewpoints of the coupling of jets to the medium: the naive perturbative approach based on a leading order calculation and the AdS/CFT correspondence for strongly coupled plasmas. I will briefly invoke in the final part of my talk the various questions that remain to be addressed. Indeed, despite the recent progress much remains to be understood about jet fragmentation in a dense medium in order to construct a systematic and predictive approach to jet-quenching from first principles.
-
Nuclear Physics Seminar
"A Nuclear Physicist's Journey In Business: Lessons From the Front Office"
Presented by Daniel Magestro, Ph.D., International Institute for Analytics
Monday, January 25, 2016, 11 am
Large Seminar Room, Bldg. 510Hosted by: Oleg Eyser
Companies in every industry are continually increasing their usage of large data sets and advanced statistical methods to understand customers and markets, improve operations, and forecast future business needs. The corresponding business demand for skilled analytical talent and "data scientists" has created a large talent gap for many companies that is predicted to surpass 100,000 nationally. Much of the talent gap arises from the hybrid skill set needed by data scientists that combines problem solving, technical, and communication skills. I will argue that the uniquely broad skill set of research scientists, and particularly experimental physicists in large collaborations, can bridge the growing talent gap for truly innovative companies.
-
Particle Physics Seminar
"Cross correlations with CMB secondaries: constraining cosmological parameters and cluster astrophysics"
Presented by Nick Battaglia, Princeton University
Thursday, January 21, 2016, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Anze Slosar
High resolution CMB experiments, such as ACT, SPT, and the Planck satellite are making precision measurements of the secondary anisotropies caused by the thermal Sunyaev Zel'dovich (tSZ) effect from galaxy clusters. However, our ability to obtain cosmological information from this tSZ signal is limited by our theoretical understanding of the baryons in clusters and groups. I will discuss how cross-correlation methods are providing new windows into the messy "Gastrophysics" of the intracluster medium and the potential for these methods to constrain various cosmological parameters.
-
Physics Colloquium
"A bottom-up approach to modeling the sensory cortex"
Presented by Luca Mazzucato, Stony Brook University
Tuesday, January 19, 2016, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Robert Pisarski
In response to sensory stimulation, neurons can generate sequences of complex activation patterns. Yet, neurons in the sensory cortex are active even in the absence of overt sensory stimulation, producing a large amount of 'ongoing,' i.e. spontaneously generated, neural activity that is often indistinguishable from noise. Research in the last two decades suggests that ongoing neural activity may shed light on the architecture and dynamics of neural circuits. Here, I present a new framework encompassing both ongoing and stimulus-evoked neural activity, combining hidden Markov model analysis of neural recordings with biologically realistic models of cortical networks based on spiking neurons. This framework has been applied successfully to the sensory cortex and can be extended to other cortical systems. In the taste system, it has revealed new properties of single neurons and of neural populations, including a reduction of multi-stability and neural dimensionality in response to sensory stimuli, pointing to the existence of local neural clusters (yet to be experimentally confirmed). Using the analytical tools of effective mean field theory, one can explain these properties as emergent features of the network dynamics.
-
Particle Physics Seminar
"Search for Higgs Bosons produced in association with top quarks with the ATLAS detector"
Presented by Professor Vivek Jain, SUNY Albany
Thursday, January 14, 2016, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Ketevi Assamagan
Due to the large measured mass of the top quark, the Yukawa coupling of the top quark (yt) is much stronger than that of other quarks. The observation of the t¯tH production mode would allow for a direct measurement of this coupling, to which other Higgs production modes are only sensitive via loop effects. Since yt is expected to be close to unity, it is also argued to be the quantity that might give insight into the scale of new physics. Using various Higgs decay modes, we report on the status of this search using data collected with the ATLAS detector at 7 and 8 TeV collision energies.
-
RIKEN Lunch Seminar
"Confinement and Chiral symmetry breaking from an Interacting Instanton-dyon ensemble for 2 colors and Nf flavors"
Presented by Rasmus Larsen, Stony Brook University
Thursday, January 14, 2016, 12:30 pm
Building 510 Room 2-160Hosted by: Daniel Pitonyak
I will present numerical results based on an interacting ensemble of instanton-dyons, that explains the connection between chiral symmetry breaking and confinement. The instanton-dyons have the nice properties to behave as monopoles at low temperatures, and as instantons at high temperatures. We will see how the scaling behavior of the instanton-dyons creates a Polyakov loop dependent potential, which forces the Polyakov loop to the confining value as the density of dyons increases at lower temperatures. For 2 flavors we find that the dominating configuration in the ensemble exhibit a chiral symmetry transition at the same temperature as the confinement transition, within accuracy. The important factor in explaining confinement and chiral symmetry breaking is the density of the Instanton-dyons.
-
Physics Colloquium
"From neV to MeV: Short-Range Fermion"
Presented by Or Hen, Laboratory for Nuclear Science, MIT
Tuesday, January 12, 2016, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Robert Pisarski
The atomic nucleus is composed of two different kinds of fermions, protons and neutrons. If the protons and neutrons did not interact, the Pauli exclusion principle would force the majority fermions, usually neutrons, to higher average momentum. In this talk I will present results from high-energy proton and electron scattering experiments, which show that short-range interactions between the fermions form correlated, high-momentum, neutronproton pairs. Thus, in neutron-rich nuclei the probability of finding a highmomentum (k>kFermi) proton (a minority Fermion) is greater than that of a neutron (a majority Fermion). This has wide ranging implications for atomic, nuclear, atomic, and astro physics, including neutrino-nucleus interactions, the EMC effect, the NuTeV anomaly, the nuclear symmetry energy and more. This feature is universal for imbalanced interacting Fermi systems and can also be observed experimentally in two-spin states ultra-cold atomic gas systems.
-
Nuclear Physics Seminar
"Short-Range Correlations in Nuclei â€" Current Status and Future Perspectives"
Presented by Or Hen, Laboratory for Nuclear Science, MIT
Tuesday, January 12, 2016, 11 am
Small Seminar Room, Bldg. 510Hosted by: Oleg Eyser
Results from recent experiments show that short-range interactions between the fermions form correlated, high-momentum, neutron-proton pairs. These pairs account for 20% - 25% of the nucleons in medium and heavy nuclei and dominate the momentum distribution of nucleons above the Fermi momentum of the nucleus. The observed dominance of these Short-Range Correlated (SRC) pairs by neutron-proton pairs shows the dominance of the tensor part of the nucleon-nucleon interaction at short distances. Recent works have shown that the existence and nature of SRC pairs has wide ranging implications for atomic, nuclear and astro physics, including neutrino-nucleus scattering, the EMC effect, the NuTeV anomaly, the nuclear symmetry energy. In this talk I will present the use of hard exclusive reactions for the study of SRCs, and discuss several open questions for next-generation experiment to address. I will present an experimental program based on proton, electron, and neutrino beams that can run at Dubna, GSI, JLab, Fermilab and perhaps even at BNL. I will also discuss the possibility of studying SRC pairs and their partonic structure at an EIC, using the method of spectator tagging in Quasi-elastic and Deep-Inelastic kinematics.
-
Particle Physics Seminar
"Reactor Antineutrino Flux and Spectrum"
Presented by Mr. Chao Zhang, BNL
Thursday, January 7, 2016, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Xin Qian
Nuclear reactors are one of the most intense, pure, controllable, cost-effective, and well-understood sources of neutrinos. Reactors have played a major role in the study of neutrino oscillations, a phenomenon that indicates that neutrinos have mass and that neutrino flavors are quantum mechanical mixtures. Accurate knowledge of reactor antineutrino production was crucial for those reactor experiments to achieve their goals. With the newest measurements from Daya Bay, I will revisit our current understanding of reactor antineutrino flux and spectrum, and its implications to future experiments.
-
Condensed-Matter Physics & Materials Science Seminar
"Electron Transport through a Proximitized Nanowire"
Presented by Leonid Glazman, Yale University
Thursday, January 7, 2016, 1:30 pm
Bldg. 734, ISB Conf. Rm. 201 (upstairs)Hosted by: Alexei Tsvelik
Motivated by recent experiments on InAs nanowires with epitaxial Al we investigate the two-terminal conductance of a short proximitized nanowire. We identify the leading electron transport processes at zero applied magnetic field as well as at finite fields, which suppress the induced superconducting gap and drive the system towards the topological transition. In the conventional superconducting phase, the conductance is controlled by the sequential Cooper pair tunneling if the induced gap exceeds the charging energy of the nanowire, and by the elastic single-electron processes if the gap becomes smaller than the charging energy. The latter mechanism yields smaller values of the linear conductance and strongly asymmetric Coulomb blockade peaks, which may explain some experimental findings. Finally, we develop a quantitative theory for the conductance evolution across the transition into the topologically-nontrivial phase.
-
Physics Colloquium
"Search for hidden sector and invisible particles in the decay of the Higgs boson"
Presented by Ketevi Assamagan, BNL
Tuesday, January 5, 2016, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Peter Petreczky
The discovery of a Higgs boson at the LHC opens new research areas for instance the search for beyond-the-Standard-Model physics in the decays of the discovered Higgs boson. In events with large missing energy associated with jets, we search for the vector boson fusion production of the Higgs boson with forward jets, and the Higgs boson decays to invisible particles that result in large missing energy in the detector. An interpretation is done for the search for dark matter as a weakly interacting massive particle (WIMP) in the Higgs boson decays. We further carry out a statistical combination with other searches of Higgs boson decays to invisible particles to improve sensitivity. The current ATLAS exclusion limit combining all these searches is the best limit so far at the LHC on the invisible decay of the Higgs boson and the Higgs portal dark matter. In data events with four leptons in the final state, consistent with the decay of the Higgs boson to four leptons, we search for light-beyond-the-Standard-Model gauge boson Zdark that decay to a pair of same flavor and opposite sign leptons (electrons or muons): H -> Z(Zdark) Zdark -> 4l. The light gauge boson Zdark is predicted in extensions to the Standard Model to explain the muon g-2 anomaly and provide a candidate for dark matter.
-
RIKEN Lunch Seminar
"Baryon interactions from Lattice QCD by Luscher's finite volume method and HAL QCD method"
Presented by Takumi Iritani, Stony Brook University
Thursday, December 17, 2015, 12:30 pm
Building 510 Room 2-160Hosted by: Hiroshi Oki
Both Luscher's finite volume method and HAL QCD method are used to analyze the hadron-hadron interaction in lattice QCD. However, some systematic discrepancies are reported between them.For example, Luscher's method shows the bound states of both deuteron and di-neutron at the heavy pion mass,while these channels are scattering states from HAL QCD method. In this talk, to understand the deviations between them, we investigate the baryon interaction from both methods with the same lattice setups.From a systematic comparison of two methods, we clarify the problems in the previous studies. We also discuss the improvement of the analyses.
-
Physics Colloquium
"Experimental study of chiral and matter-antimatter symmetries at RHIC"
Presented by Aihong Tang, BNL
Tuesday, December 15, 2015, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Peter Petreczky
Symmetries and the physics laws that they dictate are fundamental in describing the physical world. In this talk I discuss two fundamental symmetries that are well suited to be studied at RHIC, namely, the chiral symmetry and the matter-antimatter symmetry. Under the hot and dense condition at RHIC, quarks and gluons are set free from protons and neutrons, making it feasible for the chiral symmetry to be restored. A restored chiral symmetry is a necessary requirement for the Chiral Magnetic Wave (CMW), a novel QCD phenomena, to propagate. The CMW has experimental consequences — it leads to the separation of elliptic flow between charged pions, which will be discussed in this talk. On the other hand, the abundantly produced antimatter at RHIC offers a unique opportunity to study the matter-antimatter symmetry. In particular the nuclear force between two antinucleons has not been measured previously, although the corresponding force for nucleons or nuclei has been well studied for decades. In this talk I will discuss the measurement of the nuclear force between two antiprotons and compare to that between protons. As direct information on the interaction between two antiprotons, one of the simplest systems of antinucleons, this result provides an elemental ingredient for understanding the structure of more complex antinuclear and their properties.
-
Nuclear Physics Seminar
"New surprises from RHIC-Spin: forward neutron transverse single spin asymmetry from p+A collisions from PHENIX"
Presented by Alexander Bazilevsky, BNL
Tuesday, December 15, 2015, 11 am
Small Seminar Room, Bldg. 510Hosted by: Oleg Eyser
A surprisingly large transverse single spin asymmetry (A_N) in forward neutron production was discovered during the first polarized proton RHIC run in 2002. It was immediately utilized for monitoring proton beam polarization in experimental collision regions at RHIC. Later it was shown that one pion exchange model for forward neutron production was successful to describe both cross section and A_N. RHIC new data from polarized proton on nucleus collisions from RHIC 2015 run brought new surprise - a strong dependence of the asymmetry on nucleus size (or charge). Results also were found to strongly depend on particle production in other rapidity regions, indicating that there might be multiple neutron production mechanisms generating single spin asymmetry.
-
Condensed-Matter Physics & Materials Science Seminar
"Soft mode branches, quantum central peak, and strong isotropic negative thermal expansion above a perovskite quantum phase transition"
Presented by Jason Hancock, University of Connecticut
Monday, December 14, 2015, 1:30 pm
ISB Conf. Room 201 (upstairs), Bldg. 734Hosted by: Mark Dean
The importance of perovskite-structured materials to modern science cannot be understated, as they harbor diverse behavior and landscape of novel competing and intertwined phases. The structural phases of perovskites are critical to defining the framework of electronic conduction and magnetic exchange pathways in this interesting and technologically relevant class of materials. Large, isotropic negative thermal expansion is known to exist in only a handful of materials, beginning with the discovery of ZrW2O8 in the 1990s. In 2010, perovskite fluoride ScF3 was discovered to have a similarly profound negative thermal expansion (NTE) effect, shrinking in response to heat over a 1000 K temperature window with a linear thermal expansion coefficient lower than -10-5/K. Another curious property of this material is the structural stability â€" ScF3 retains a simple cubic structure and four atom unit cell from cryogenic temperature to its high melting point of 1800 K. ScF3 material does not feature the interesting phase competition of electrons and spin enjoyed by many of its oxide and fluoride cousins and can be classified as an ionic insulator. However the superlative nature of the NTE effect has motivated us to dive deeply into the lattice dynamics using high energy resolution inelastic X-ray scattering on strain-free single crystals. Surprisingly, we find that an entire optical mode branch circumscribing the Brillouin zone boundary softens to nearly zero frequency as the temperature T approaches T=0. ScF3 at T=0 thus sits in extreme proximity to a quantum phase transition. We interpret this result in the context of better studied trifluorides and examine in detail the disorder phase diagram. In addition, concomitant with softening of the optic branch, a quasielastic "central peak" (CP) emerges and strengthens toward low temperature, further bolstering the identification of a T=0 phase transition. The CP phe
-
Nuclear Theory/RIKEN seminar
"Evolution of gluon TMDs: from small to moderate x"
Presented by Andrey Tarasov, Jefferson Lab
Friday, December 11, 2015, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Soeren Schlichting
Recently we obtained an evolution equation for gluon TMDs, which addresses a problem of unification of different kinematic limits. It describes evolution in the whole range of Bjorken x and transverse momentum k⊥. I plan to discuss this evolution equation and show how in different kinematic regimes it yields several well-known and some previously unknown results.
-
Particle Physics Seminar
"Kinematic weak lensing"
Presented by Eric Huff, Ohio State University
Thursday, December 10, 2015, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Erin Sheldon
Kinematic measurements hold some promise of dramatically enhancing the prospects of traditional weak lensing. In this talk I outline the method and describe how it eliminates or suppresses the effects of traditional weak lensing systematic errors arising from shear calibration, photometric redshifts, and intrinsic alignments. I also discuss what it would take to scale kinematic lensing up to a level competitive with other advanced dark energy probes.
-
Condensed-Matter Physics & Materials Science Seminar
"Magnetotransport in Weyl and Dirac Metals"
Presented by Gustavo Monteiro, Stony Brook University
Thursday, December 10, 2015, 1:30 pm
ISB Building, Room 201Hosted by: Alexei Tsvelik
Dirac (Weyl) metals are characterized by the linear dispersion of electron quasiparticles, with the Dirac (Weyl) point hidden inside a Fermi surface. In this talk, I will refer to the so-called chiral kinetic theory to describe within the same framework both the negative magnetoresistance caused by the chiral magnetic effect (CME) and quantum oscillations in the magnetoresistance (SdH effect) due to the existence of the Fermi surface in these materials. I will also argue about the role of Fermi arcs and their contribution for the SdH modes. At last, I will discuss the relevance of obtained results to recent measurements on Cd As .
-
RIKEN Lunch Seminar
"Phase structure of lattice QCD with Wilson and twisted-mass fermions including isospin breaking"
Presented by Derek Horkel, University of Washington
Thursday, December 10, 2015, 12:30 pm
Building 510 Room 2-160Hosted by: Hiroshi Oki
As the precision frontier of particle physics continues to develop, the field of lattice QCD has risen to the challenge. Modern lattice simulations, have increasingly included light non-degenerate up and down quark masses and electromagnetism. Previously answered questions about the vacuum structure of QCD on the lattice must be reexamined when these isospin breaking effects are included. If not careful, lattice practitioners may simulate in non-physical phases which cannot be extrapolated to the continuum limit. Using chiral perturbation theory, I will discuss where these non-physical phases can arise for Wilson and twisted mass fermions. I will also explain some of the complications which arise when tuning the up and down twisted quark masses to their critical values in the presence of electromagnetism.
-
Physics Colloquium
"What Stubs and Sparkles Will Tell Us About Exploding Stars"
Presented by Kate Scholberg, Duke University
Tuesday, December 8, 2015, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Peter Petreczky
When a massive star collapses at the end of its life, nearly all of the gravitational binding energy of the resulting remnant is released in the form of neutrinos. I will discuss the nature of the core-collapse neutrino burst and what we can learn about particle physics and about astrophysics from the detection of these neutrinos. I will cover supernova neutrino detection techniques in general, current supernova neutrino detectors, and prospects for specific future experiments.
-
Nuclear Physics Seminar
"Measurement of the transverse single-spin asymmetry in p+p->W±/Z0 at RHIC"
Presented by Salvatore Fazio, BNL
Tuesday, December 8, 2015, 11 am
Small Seminar Room, Bldg. 510Hosted by: Oleg Eyser
We present the measurement of the transverse single-spin asymmetry of weak boson production in transversely polarized proton-proton collisions at s√=500 GeV by the STAR experiment at RHIC. The measured observable is sensitive to the Sivers function, one of the transverse momentum dependent parton distribution functions, which is predicted to have the opposite sign in proton-proton collisions from that observed in deep inelastic lepton-proton scattering. These data provide the first experimental investigation of the non-universality of the Sivers function, fundamental to our understanding of QCD. The measured observable is also sensitive to the currently unconstrained Sivers function for the sea-quarks and to the evolution of the transverse-momentum dependent distribution functions.
-
Nuclear Theory/RIKEN Seminar
"Semi-classics, complex saddles and real path integrals"
Presented by Tin Sulejmanpasic, North Carolina State University
Friday, December 4, 2015, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Soeren Schlichting
I will discuss the use of semi-classics and instanton calculus and argue that, contrary to common wisdom, complex solutions of the equations of motion are a necessary ingredient of any semi-classical expansion. In particular, I will show that without the complex solutions semi-classical expansion of supersymmetric theories cannot be reconciled with supersymmetry. This has a natural interpretation in the Picard-Lefschetz theory.
-
RIKEN Lunch Seminar
"Sterile neutrino dark matter produced after the QCD phase transition"
Presented by Louis Lello, University of Pittsburgh
Thursday, December 3, 2015, 12:30 pm
Building 510 Room 2-160Hosted by: Daniel Pitonyak
Sterile neutrinos are SU(2) singlets that mix with active neutrinos via a mass matrix, its diagonalization leads to mass eigenstates that couple via standard model vertices. We study the production of sterile neutrinos in the early universe from pion decays shortly after the QCD phase transition in the absence of a lepton asymmetry. We introduce the quantum kinetic equations that describe their production, freeze out and decay and discuss the various processes that lead to their production in a wide range of temperatures assessing their feasibility as dark matter candidates. We consider the production of heavy neutrinos in the mass range < 140MeV from pion decay shortly after the QCD crossover including finite temperature corrections to the pion form factors and mass. We consider the different decay channels that allow for the production of heavy neutrinos showing that their frozen distribution functions exhibit effects from "kinematic entanglement" and argue for their viability as mixed dark matter candidates. We discuss abundance, phase space density and stability constraints and argue that heavy neutrinos with lifetime >1/H0 freeze out of local thermal equilibrium.
-
Physics Colloquium
"Exotic Hadrons"
Presented by Eric Swanson, University of Pittsburgh
Tuesday, December 1, 2015, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Peter Petreczky
A series of novel and unusual hadrons have been discovered since 2003. This talk will present an overview of these states with the purpose of learning what they reveal about the nonperturbative structure of Quantum Chromodynamics.
-
Nuclear Theory/RIKEN Seminar
"Transversity Distribution and Collins Fragmentation Functions with QCD Evolution"
Presented by Alexei Prokudin, Jefferson Lab
Friday, November 20, 2015, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Soeren Schlichting
We study the transverse momentum dependent (TMD) evolution of the Collins azimuthal asymmetries in e+eâˆ' annihilations and semi-inclusive hadron production in deep inelastic scattering (SIDIS) processes. All the relevant coefficients are calculated up to the next-to-leading logarithmic (NLL) order accuracy. By applying the TMD evolution at the approximate NLL order in the Collins-Soper-Sterman (CSS) formalism, we extract transversity distributions for u and d quarks and Collins fragmentation functions from current experimental data by a global analysis of the Collins asymmetries in back-to-back di-hadron productions in e+eâˆ' annihilations measured by BELLE and BABAR Collaborations and SIDIS data from HERMES, COMPASS, and JLab HALL A experiments. The impact of the evolution effects and the relevant theoretical uncertainties are discussed. We further discuss the TMD interpretation for our results, and illustrate the unpolarized quark distribution, transversity distribution, unpolarized quark fragmentation and Collins fragmentation functions depending on the transverse momentum and the hard momentum scale. We make detailed predictions for future experiments and discuss their impact.
-
HET/RIKEN Lunch Seminar
"Collider Phenomenology of the Right Handed Heavy Neutrinos"
Presented by Arindam Das, University of Alabama
Friday, November 20, 2015, 12 pm
Building 510 Room-2-160Hosted by: Amarjit Soni
We study the collider signature of pseudo-Dirac heavy neutrinos in the inverse seesaw scenario, where the heavy neutrinos with mass at the electro-weak scale can have sizable mixings with the Standard Model neutrinos, while providing the tiny light neutrino masses by the inverse seesaw mechanism. Based on a simple, concrete model realizing the inverse seesaw scenario, we fix the model parameters so as to reproduce the neutrino oscillation data and to satisfy other experimental constraints, assuming two typical flavor structures of the model and the different types of hierarchical light neutrino mass spectra. For completeness, we also consider a general parametrization for the model parameters by introducing an arbitrary orthogonal matrix and the nonzero Dirac and Majorana phases. We perform a parameter scan to identify an allowed parameter region which satisfies all experimental constraints. With the fixed parameters, we analyze the heavy neutrino signal at the LHC through trilepton final states with large missing energy and at the ILC through a single lepton plus dijet with large missing energy.
-
Brookhaven Women In Science (BWIS) Event
"Thousand Shades of Grey: From High School Intern to Medical Imaging Physics Graduate"
Megan Russ, University of Buffalo Toshiba Stroke and Vascular Research Center
Thursday, November 19, 2015, 4:30 pm
Large Seminar Room, Bldg. 510Refreshments served before the talk.
-
RIKEN Lunch Seminar
"Viscous Velocity Gradient Correction to Thermal Photon Emission Rate at Strong Coupling"
Presented by Kiminad Mamo, University of Illinois at Chicago
Thursday, November 19, 2015, 12:30 pm
Building 510 Room 2-160Hosted by: Daniel Pitonyak
We compute the correction to the thermal photon emission rate in first order of shear components of fluid velocity gradients in near-equilibrium hydrodynamic plasma at strong coupling regime using the real-time Schwinger-Keldysh formalism in AdS/CFT correspondence. We find that the gradient correction to the thermal photon emission rate at strong coupling is about 0.3 - 0.4 times of the equilibrium rate.
-
Physics Colloquium
"IceCube: the High-energy Universe and Multimessenger Astrophysics with Neutrinos"
Presented by Imre Bartos, Columbia University
Tuesday, November 17, 2015, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Peter Petreczky
Astrophysical processes that produce the observed energetic cosmic particles (up to 10^20 eV) and high-energy gamma radiation involve extreme non-thermal acceleration, strongly constraining the list of possible sources. Nevertheless, the origin of the most energetic cosmic rays, and the electromagnetic emission mechanism in extreme sources such as gamma-ray bursts, are currently unknown. Neutrinos may well be the silver bullet to unravel these processes. They can reveal the hadronic nature of the emission, and due to their weak interaction they lead right back to the source. The IceCube neutrino observatory at the South Pole has recently discovered a cosmic flux of TeV-PeV neutrinos, making the first step in lifting the curtain on cosmic particle accelerators. I will discuss recent multimessenger observational developments, and source candidates in the high-energy universe. I will describe plans and capabilities for the next-generation neutrino detector IceCube-Gen2.
-
Nuclear Physics Seminar
"PHENIX measurements of single electrons from semi-leptonic charm and bottom hadron decays in Au+Au collisions"
Presented by Dr. Darren McGlinchey, University of Colorado, Boulder
Tuesday, November 17, 2015, 11 am
Small Seminar Room, Bldg. 510Hosted by: Jin Huang
Measurements of the modification of heavy quarks in heavy ion collisions provide constraints on energy loss in the Quark Gluon Plasma. The dead cone effect predicts a mass ordering to the modification, with the heavier bottom quark being less modified than the charm quark due to suppression of forward radiation. Therefore, measuring the modification of charm and bottom quarks separately can provide additional constraints on energy loss calculations. Previous PHENIX measurements of heavy flavor electrons indicated a substantial suppression relative to binary scaled p+p collisions at high transverse momentum. However, the inability to separate the contributions from charm and bottom hadron decays prevented a full understanding of the modification. Using the precise tracking capabilities provided by the PHENIX barrel Silicon Vertex Detector (VTX), we are now able to separate the contributions from charm and bottom hadrons to the measured heavy flavor electrons as a function of transverse momentum in Au+Au collisions at sqrt(s_NN)=200 GeV. These results will be discussed and compared with theoretical models.
-
Nuclear Theory/RIKEN Seminar
"Linearly resummed hydrodynamics from gravity"
Presented by Yanyan Bu, Ben Gurion University of the Negev
Friday, November 13, 2015, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Soeren Schlichting
Using fluid/gravity correspondence, we study all-order resummed hydrodynamics in a weakly curved spacetime. The underlying microscopic theory is a finite temperature \mathcal{N}=4 super-Yang-Mills theory at strong coupling. To linear order in the amplitude of hydrodynamic variables and metric perturbations, the fluid's stress-energy tensor is computed with derivatives of both the fluid velocity and background metric resummed to all orders. In addition to two viscosity functions, we find four curvature induced structures coupled to the fluid via new transport coefficient functions, which were referred to as gravitational susceptibilities of the fluid (GSF). We analytically compute these coefficients in the hydrodynamic limit, and then numerically up to large values of momenta. We extensively discuss the meaning of all order hydrodynamics by expressing it in terms of the memory function formalism, which is also suitable for practical simulations. We also consider Gauss-Bonnet correction in the dual gravity, which is equivalent to some 1/N corrections in the dual CFT. To leading order in the Gauss-Bonnet coupling, we find that the memory function is still vanishing.
-
Joint RIKEN Lunch/HET Seminar
"Gluon-fusion Higgs production: the final frontier"
Presented by Elisabetta Furlan, ETH, Zurich
Thursday, November 12, 2015, 12:30 pm
Building 510 Room 2-160Hosted by: Tomomi Ishikawa
The gluon-fusion Higgs production cross section has been recently computed through the next-to-next-to-next to leading order (N^3LO) in QCD. This unprecedented level of accuracy is crucial to exploit fully the LHC data in the validation of the Standard Model and in the search for potential (small) deviations due to new physics. I will give an overview of the tools that we employed to achieve this result, from the framework of heavy-quark effective theories to the analytical and mathematical machinery that we developed. I will conclude with some results and future prospects.
-
Nuclear Theory/RIKEN Seminar
"Massless QED in three dimensions with even number of flavors"
Presented by Rajamani Narayanan, Florida International University
Friday, November 6, 2015, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Soeren Schlichting
Massless QED in three (two space and one Euclidean time) with even number of flavors does not break parity. There are analytical arguments for chiral symmetry to be spontaneously broken and some numerical evidence supporting these arguments. An interesting "open" question is the possibility of a critical number of flavors below which chiral symmetry is broken. Numerical results obtained using dynamical Wilson fermions will be presented with emphasis on the behavior of the low lying eigenvalues of the Wilson Dirac operator. Finite volume analysis will be used to obtain conclusions about the absence or presence of a chiral condensate.
-
Particle Physics Seminar
"LAr TPC data reconstruction"
Presented by Dorota Stefan, CERN/NCBJ Warsaw Poland
Thursday, November 5, 2015, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Elizabeth Worcester
In recent years, there is much interest in building massive liquid argon time projection (LAr TPC) detectors to measure among others CP violation in leptonic sector, search for nucleon decay and study a core-collapse supernova via neutrinos. Data collected by ICARUS and ArgoNuet proved that LAr TPC calorimetric and spatial resolutions are excellent. The detector technology with no doubts is much advanced, resulting with plans for the next generation of liquid argon experiments: the short baseline (SBN) and the long baseline (DUNE) are on the horizon. The LAr TPC evolved from the bubble chambers preserving the high resolution of tracking. Data analysis requires automatic event reconstruction that can understand and efficiently use the high granularity images provided by detector. The talk will cover the most recent advances in the reconstruction techniques, and also possible ways of developments since we are still on the way towards the ultimate tool for the optimal data analysis.
-
Condensed-Matter Physics & Materials Science Seminar
"Pixelated detection in Differential Phase Contrast Interesting properties of pixelated STEM"
Presented by Matus Krajnak, University of Glasgow, United Kingdom
Thursday, November 5, 2015, 11 am
Bldg.480 Conf. RmHosted by: Yimei Zhu
The application of differential phase contrast (DPC) imaging to the study of polycrystalline magnetic thin films and nanostructures in scanning transmission electron microscopy (STEM) has been hampered by the strong diffraction contrast resulting from the granular structure of the materials. In my talk I will demonstrate how a pixelated detector has been used to detect the bright field disk in aberration corrected STEM. I will explain subsequent processing of the acquired data, which allows efficient enhancement of the magnetic contrast in the resulting images. Initial results from a charged coupled device (CCD) camera demonstrate the highly efficient nature of this improvement over previous methods. Further hardware development with the use of a direct radiation detector, the Medipix3, also shows the possibilities where the reduction in collection time is more than an order of magnitude compared to the CCD. This allows subpixel measurement of the beam deflection due to the magnetic induction. Whilst the detection and processing is data intensive we have demonstrated highly efficient DPC imaging whereby pixel by pixel interpretation of the induction variation is realised with great potential for nanomagnetic imaging. In my talk I will also show advantages of using pixelated DPC in imaging of magnetic skyrmion structures in single crystal FeGe helimagnet which can provide their inner structure. I will advocate for pixelated STEM and explain how advantageous it can be in standard experiments and point to some new developments which it can provide.
-
C-AD Accelerator Physics Seminar
"On the Development, Characterization, and Application of New Extraction Chromatographic Resins"
Presented by Dr. Steffen Happel, TRISKEM
Monday, November 2, 2015, 4 pm
Bldg. 911B, Large Conf. Rm. Rm.A202Hosted by: Dmitri Medvedev
«An overview will be given over a number of new extraction chromatographic resins that have been developed over the last few years. Further to characterisation data (mainly DW values of selected elements) their application in various domains will be discussed. Examples given will include decommissioning and radioactive waste monitoring (e.g. Cl-36/I-129 and Sn-126), environmental monitoring (e.g. direct extraction and separation of Pb and Sr from aqueous samples) and the production of isotopes for medical purposes (e.g. production of Cu isotopes from Ni or Zn targets, the separation of Zr from Y targets and the separation of Sn from large Cd targets)."
-
Nuclear Theory/RIKEN Seminar
"Observable consequences of event-by-event fluctuations of HBT radii"
Presented by Christopher J. Plumberg, Ohio State University
Friday, October 30, 2015, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Soeren Schlichting
One of the major lessons from the field of heavy-ion physics in the past several years has been the significance of the role played by event-by-event fluctuations in the evolution of a heavy-ion collision. Their important effects on many momentum-space observables (particle yields and spectra, anisotropic flows, etc.) have already been studied systematically, and some of the properties of their event-by-event distributions, and their consequences for the extraction of medium properties such as the specific viscosity of the quark-gluon plasma (QGP), are already known. In this talk it is pointed out that similar event-by-event fluctuations of spatiotemporal observables provide complementary constraints on our understanding of the dynamical evolution of heavy-ion collisions. The relation of Hanbury Brown-Twiss (HBT) radii extracted from ensemble-averaged correlation function measurements to the mean of their event-by-event probability distribution is clarified, and a method to experimentally determine the mean and variance of this distribution is proposed and demonstrated using an ensemble of fluctuating events generated with the viscous hydrodynamic code VISH2+1. The sensitivity of the mean and variance of the HBT radii to the specific QGP shear viscosity η/s is studied using simulations with the same code. We report sensitivity of the mean pion HBT radii and their variances to the temperature dependence of η/s near the quark-hadron transition at a level similar (10-20%) to that which was previously observed for elliptic and quadrangular flow of charged hadrons.
-
Condensed-Matter Physics & Materials Science Seminar
"The Internal Structure of a Vortex in a Two-Dimensional Superfluid with Long Healing Length"
Presented by Igor Aleiner, Columbia University
Thursday, October 29, 2015, 2 pm
Bldg. 734, ISB Conf. Rm. 201Hosted by: Alexei Tsvelik
We analyze the motion of quantum vortices in a two-dimensional bosonic superfluid within Popov's hydrodynamic description. In the long healing length limit (where a large number of particles are inside the vortex core) the superfluid dynamics is determined by saddle points of Popov's action, which, in particular, allows for weak solutions of the Gross-Pitaevskii equation. We solve the resulting equations of motion for a vortex moving with respect to the superfluid and find the reconstruction of the vortex core to be a non-analytic function of the force applied on the vortex. This response produces an anomalously large dipole moment of the vortex and, as a result, the spectrum associated with the vortex motion exhibits narrow resonances lying {\em within} the phonon part of the spectrum, contrary to traditional view. (in collaboration with O. Agam and A. Klein)
-
Condensed-Matter Physics & Materials Science Seminar
"MITs, magnetism, and dopants: Probing the nanoscale using advanced STEM"
Presented by Jack Y. Zhang, University of California Santa Barbara
Thursday, October 29, 2015, 11 am
Bldg.480 Conf. RmHosted by: Yimei Zhu
Perovskite oxides remain a material class with properties that are still difficult to predict. Strong electron correlations, coupling between electron, lattice, spin and orbital degrees of freedoms, combined with the versatility of the structure itself, result in a wide range of properties and unique emergent phenomena that only occur at heterointerfaces. Understanding the origin of these properties is the first step to successfully control and tailor these materials for useful application. To that end, we utilize the scanning transmission electron microscope to characterize a number of titanate and nickelate compounds, in order to develop a link between the atomic structure and electrical/magnetic properties. Using real-space and diffraction techniques, we can probe the local atomic structures of thin film interfaces and quantum wells. We also continue the development of using quantitative STEM intensities for precise and accurate determination of 3D dopant atom configurations. Using variable detector angles, we demonstrate an improvement in 3D dopant locations on a test sample.
-
Nuclear Theory/RIKEN Seminar
"Thermal photons from a modern hydrodynamical model of heavy ion collisions"
Presented by Jean-Francois Paquet, Stonybrook University
Friday, October 23, 2015, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Soeren Schlichting
Early fluid-dynamical calculations of direct photon spectra and momentum anisotropy were found to be systematically smaller than measurements from the RHIC and the LHC, an observation that became known as the "direct photon puzzle". I will show that the use of a modern hydrodynamical model of heavy ion collisions and of the latest photon emission rates greatly improves agreement with both ALICE and PHENIX data, supporting the idea that thermal photons are the dominant source of direct photon momentum anisotropy in heavy ion collisions. The event-by-event hydrodynamical model used includes, for the first time, both shear and bulk viscosities, along with second order couplings between the two viscosities. Calculations using different photon emission rates will be shown, including one that takes into account the effect of confinement on photon emission. The effect of both shear and bulk viscosities on the photon rates will be shown to have a measurable effect on the photon momentum anisotropy.
-
Particle Physics Seminar
"Light Sterile Neutrinos: An Experimental Overview"
Presented by Jonathan Link, Center for Neutrino Physics, Virginia Tech
Thursday, October 22, 2015, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Elizabeth Worcester
Persistent, unproven hints of an eV-scale sterile neutrino have been around since the late 1990's, when the LSND signal was shown to be incompatible with the emerging 3-neutrino oscillation framework. More recent results from MiniBooNE and T2K as well as reanalyses of reactor neutrino and gallium source data continue to suggest the possibility of this new physics, but no experiment has been able to definitively demonstrate or for that matter rule out their existence. This talk will review the current state of the sterile neutrino and examine one possible experimental test using a new reactor neutrino detector technology designed to address the particular challenges of a short-baseline reactor neutrino experiment.
-
RIKEN Lunch Seminar
"Walking and conformal dynamics in many-flavor QCD"
Presented by Hiroshi Ohki, RIKEN BNL Research Center
Thursday, October 22, 2015, 12:30 pm
Building 510 Room 2-160Hosted by: Tomomi Ishikawa
We present our lattice results of SU(3) gauge theory with many flavors, in particular with Nf=8, as a model of a walking or conformal gauge theory. We study the scaling properties of various hadron spectra including the (pseudo)scalar, vector, and baryon channels. From the Nf dependence of the theory, possible signals of walking or conformal dynamics will be discussed.
-
HET/RIKEN Seminar
"Phenomenology of semileptonic B-meson decays with form factors from lattice QCD"
Presented by Ran Zhou, Fermilab
Wednesday, October 21, 2015, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Tomomi Ishikawa
The exclusive semileptonic $B$-meson decays $B\to K(\pi)\ell^+\ell^-$, $B \to K(\pi)\nu\bar\nu$, and $B\to\pi\tau\nu$ are used to extract the CKM elements and probe new physics beyond Standard Model. The errors of the form factors used to be an important source of the uncertainties in the theoretical predictions. Recent developments in lattice-QCD provide more accurate form factors and enable us to have better theoretical predictions. In this talk, I will present the latest lattice-QCD results of the form factors in the semileptonic $B$-meson decays processes. In addition, I will compare the theoretical predictions and recent experimental results. The tension between the Standard Model and semileptonic $B$-meson decay experimental data will be discussed.
-
Condensed-Matter Physics & Materials Science Seminar
"Three dimensional topological semimetal Cd3As2: insights from magneto-optical spectroscopy"
Presented by Ana Akrap, University of Geneva, Switzerland
Wednesday, October 21, 2015, 1:30 pm
Bldg. 480 Conf. RoomHosted by: Chris Homes
Cd3As2 is a three-dimensional Dirac semimetal, with two Dirac cones around the Gamma point shifted away from each other along the (001) direction. It is known that the Dirac cones appear due to band inversion, although their exact scale is not clear at the moment. I will talk about zero-field optical conductivity, and high-field magneto-reflectivity of this material, and address some of the open questions regarding the band structure.
-
Condensed-Matter Physics & Materials Science Seminar
"TBA"
Presented by Sasa Dordevic, University of Akron
Tuesday, October 20, 2015, 1:30 pm
Building 734, Room 201Hosted by: Cedomir Petrovic
Infrared and magneto-optical studies of topological insulators Spectroscopic techniques are an important tool in studies of novel materials. I will review recent infrared and magneto-optical studies of 3D topological insulators Bi2Se3, Bi2Te3, Sb2Te3 and Bi1-xSbx. A number of issues will be discussed, such as the cyclotron resonance and its field dependence, electronic inhomogeneities, and electron-phonon coupling. We find that in Bi2Se3 charge carriers are indeed strongly coupled to an optical phonon, causing its asymmetric (Fano) lineshape. Moreover, we show that the asymmetry of the phonon can be switched from negative to positive, with the application of magnetic field. This is the so-called Fano q reversal, which to the best of our knowledge has not been observed before in topological insulators.
-
Condensed-Matter Physics & Materials Science Seminar
"GW+DMFT: a diagrammatically controlled ab initio theory of strong correlation in real materials"
Presented by Sangkook Choi, Rutgers University
Tuesday, October 20, 2015, 11 am
Building 734, Room 201Hosted by: Robert Konik
The first principles description of strongly-correlated materials is currently regarded as one of the greatest challenges in condensed matter physics. In contrast to the weakly-correlated materials, one-particle picture based on the Fermi liquid theory fails because electrons in strongly-correlated materials are neither fully localized on the atomic sites nor fully itinerant in the crystal. One of the most successful approaches to strongly-correlated materials is the dynamical mean field theory (DMFT). Its successes revived the interest in the long-sought goal of achieving a diagrammatically controlled ab initio theory by combining GW and DMFT Feynman graphs. In this talk, I'll introduce GW+DMFT approaches and present our new methodology grounded on the combination of the quasiparticle self-consistent GW approximation (QSGW) and DMFT. I will also show how QSGW+DMFT approach improves the spectral properties of open-d and -f shell systems in comparison to other theories. I will conclude with the challenges ahead and its potential roles in materials design.
-
Particle Physics Seminar
"Recent Results from the BaBar Experiment"
Presented by David Norvil Brown, University of Louisville
Thursday, October 15, 2015, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Ketevi A. Assamagan
The BaBar Experiment was initially designed to study CP-Violation in B-meson decays. However, due to the general-purpose and high-quality design of the detector, it has been utilized for studies of many topics beyond the weak flavor realm. I will present a selection of recent results from BaBar, including topics from B physics and beyond. The results selected include a first observation of a mode which is an interesting piece in the puzzle about baryonic B-meson decays; a measurement of time-dependent asymmetries in a B-meson decay; a measurement of Collins asymmetries in u, d, and s quark fragmentation; and a search for long-lived particles predicted in many beyond the Standard Model theories.
-
Condensed-Matter Physics & Materials Science Seminar
Presented by Sergey Zvyagin, High Magnetic Field Laboratory, Helmholtz Center Dresden, Germany
Thursday, October 15, 2015, 1:30 pm
Building 734, Room 201Hosted by: Cedomir Petrovic
Spin dynamics in triangular-lattice antiferromagnets Cs2CuBr4 and Cs2CuCl4: high-field ESR studies Sergei Zvyagin Dresden High Magnetic Field Laboratory (HLD) Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany A spin-1/2 Heisenberg antiferromagnet (AF) on a triangular lattice is the paradigmatic model in quantum magnetism and in the focus of recent experimental and theoretical studies. Here, we present results of high-field electron spin resonance (ESR) studies of spin-1/2 Heisenberg AFs Cs2CuCl4 and Cs2CuBr4 with distorted triangular-lattice structures in magnetic fields up to 50 T [1]. In the magnetically saturated phase, quantum fluctuations are fully suppressed, and the spin dynamics is defined by ordinary magnons. This allows us to accurately describe the magnetic excitation spectra in both materials and, using the harmonic spin-wave theory, to determine their exchange parameters. The approach has a broader impact and can be potentially used for any quantum magnet with reduced (e.g., by the staggered Dzyaloshinskii-Moriya interaction) translational symmetry, resulting, as predicted, in emergence of a new exchange mode above Hsat. We found that a substantial zero-field energy gap, Î"~9.5 K, observed in the low-temperature excitation spectrum of Cs2CuBr4, is present below and well above TN, being a characteristics of low-dimensional spin-correlated state. The experimental data are compared with results of model spin-wave-theory calculations for spin-1/2 triangular lattice AF. This work was supported by the DFG. [1] S. A. Zvyagin, D. Kamenskyi, M. Ozerov, J. Wosnitza, M. Ikeda, T. Fujita, M. Hagiwara, A. I. Smirnov, T. A. Soldatov, A. Ya. Shapiro, J. Krzystek, R. Hu, H. Ryu, C. Petrovic, and M. E. Zhitomirsky, Phys. Rev. Lett. 112, 077206, 2014
-
RIKEN Lunch Seminar
"pQCD thermodynamics with massive quarks"
Presented by Thorben Graf, Institut für Theoretische Physik, Johann Wolfgang Goethe-Universität
Thursday, October 15, 2015, 12:30 pm
Building 510 Room 2-160Hosted by: Daniel Pitonyak
Results for several thermodynamic quantities within the next-to-leading order calculation of the thermodynamic potential in perturbative QCD at finite temperature and chemical potential including non-vanishing quark masses are presented. These results are compared to lattice data and to higher-order optimized perturbative calculations to investigate the trend brought about by mass corrections. Furthermore, the equation of state for nonvanishing isospin density was investigated within the introduced framework and the findings are also presented.
-
Physics Colloquium
"Random Matrices in Physics"
Presented by Hans A. Weidenmuller, Max-Planck-Institut fur Kernphysik, Heidelberg, Germany
Tuesday, October 13, 2015, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Robert Pisarski
What can we say about a physical system when we know next to nothing about it? In classical physics, the principles of thermodynamics and a few system-specific parameters suffice to make predictions. In quantum physics, random matrices have similar predictive power. That approach-referred to as random-matrix theory-has found wide applications in recent years, in quantum physics and beyond. The use of random matrices in quantum chaos, in complex many-body systems, in disordered systems and in quantum chromodynamics will be presented. Furher applications in physics and mathematics will be briefly mentioned.
-
Special Nuclear Theory Seminar
"Inclusive Hadron Production as a Probe of Saturation Physics on the Energy Frontier"
Presented by David Zaslavsky, Central China Normal University
Friday, October 9, 2015, 11 am
Small Seminar Room, Bldg. 510Hosted by: Soeren Schlichting
With a foundation of almost two decades of theoretical research, the saturation formalism is widely considered a strong candidate to describe the behavior of small-x gluons in high-energy collisions. However, the formalism has proven difficult to test. There is a pressing need for precise numerical results from the saturation formalism to use in comparisons with collider data. Fortunately, recent progress in the cross section for inclusive hadron production in pA collisions shows that it may be just the kind of precise result the community needs. The calculation of the NLO corrections, starting in 2012, achieved impressive reductions in the theoretical and numerical uncertainties, although the result becomes negative at high p⊥. Still, precise predictions at moderate p⊥ can be made and tested, and could be strong evidence toward showing the viability of the saturation model. In this talk, I introduce the recent modifications to the dipole splitting functions that complete the NLO corrections and help offset the negativity observed in earlier results. I'll also present the latest numerical results for the full LO+NLO cross section, including the first comparison with LHC pilot run data. For forward rapidity at both RHIC and the LHC, we have found excellent agreement with the data throughout the range in which the calculation is valid.
-
Condensed-Matter Physics & Materials Science Seminar
"TBATopological Nodal-Line Fermions in Strong Spin-Orbit Metal PbTaSe2"
Presented by Tay-Rong Chang, National Tsing Hua University Taiwan, Taiwan
Thursday, October 8, 2015, 1:30 pm
ISB Bldg. 734, Conf. Rm. 201 (upstairs)Hosted by: Wei Ku
In a typical three-dimensional metal, the low-energy excitations are found on a two-dimensional closed Fermi surface in momentum space. Topological semimetals, by contrast, can support one-dimensional Fermi lines or zero-dimensional Fermi-Weyl points, at locations in momentum space, where the valence and conduction bands touch. While the degeneracy points in Weyl semimetals are robust against any perturbation that preserves translational symmetry, nodal lines require protection by additional crystalline symmetries such as mirror reflection. In this talk, I will demonstrate the prediction of topological nodal-line states in the non-centrosymmetric compound single-crystalline PbTaSe2 with strong spin-orbit coupling based on the first-principles electronic structure calculations. Remarkably, the spin-orbit nodal lines in PbTaSe2 are not only protected by the reflection symmetry but also characterized by an integer topological invariant. Our theoretical analysis illustrate the physical mechanism underlying the formation of the topological nodal-line states and associated surface states. The calculated surface states for (001) surface with Pb-termination are in good agreement with angle-resolved photoemission (ARPES) measurements [1]. [1] arXiv:1505.03069, G. Bian, T.-R. Chang, R. Sankar, et al.
-
Particle Physics Seminar
"Top Quark Precision Physics and the Fate of the Universe"
Presented by Andreas Jung, Purdue University
Thursday, October 1, 2015, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Ketevi A. Assamagan
The talk will discuss recent measurements in the top quark sector, the heaviest known elementary particle known so far, performed at the Fermilab Tevatron Collider and at the LHC. I will highlight Tevatron results that are competitive to those at the LHC, especially regarding the top quark mass and production asymmetry. The talk will also present CMS results on the top quark mass and Yukawa coupling. I will discuss the implications for the standard model electroweak sector regarding the vacuum stability. I will conclude with an outlook towards the high luminosity phase of the LHC and the CMS silicon detector upgrades required for the high luminosity phase.
-
Particle Physics Seminar
"Recent Results From Daya Bay"
Presented by Gaosong Li, Shanghai Jiao Tong University
Monday, September 28, 2015, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Elizabeth Worcester
The Daya Bay Reactor Neutrino Experiment is designed to measure the neutrino mixing angle ï±13 with unprecedented precision. The experiment utilizes multiple pairs of identical antineutrino detectors (ADs) at different baselines from three pairs of reactor cores to minimize systematic uncertainties. In 2012, Daya Bay made the first definitive measurement of a non-zero value for ï±13 using the first 55 days of data collected with six ADs by measuring the antineutrino rate deficit. With the final two ADs installed, Daya Bay resumed data taking in full 8-AD configuration in late 2012. More than 1 (0.15) million electron antineutrino candidates had been collected with the near (far) site detectors by the end of 2013, significantly improving the precision on ï±13. In addition to precision measurement of neutrino oscillation parameters, analyses exploring various other physics potential are carried out. In this talk, I will present the latest results on neutrino oscillation parameters, the search for a light sterile neutrino and the measurement of reactor neutrino flux and spectrum.
-
Condensed-Matter Physics & Materials Science Seminar
"Inelastic Neutron Scattering of Manganese Pnictide Compounds LaMnPO and CaMn2Sb2"
Presented by Daniel McNally, Stony Brook University/BNL
Monday, September 28, 2015, 11 am
Bldg. 480Hosted by: Mark Dean
I will report on two different projects that used inelastic neutron scattering measurements to determine 1. The origin of the charge gap in LaMnPO [1] 2. The origin of the magnetic frustration in CaMn2Sb2 [2] 1. I present my inelastic neutron scattering measurements over a wide range of temperatures on a powder sample of the antiferromagnetic insulator LaMnPO, that exhibits long range antiferromagnetic order below TN = 375 K. I used these measurements to determine a) the strength of the inter-site magnetic exchange interactions SJ1 = 34 meV, SJ2 = 10 meV b) the temperature Tmax = 700 K (>> TN) where 2D magnetic correlations are no longer important. I then present high temperature optical spectroscopy measurements on single crystals of LaMnPO that show a charge gap persists above TN and Tmax. These experimental results show that long range magnetic order and exchange interactions play only a limited role in the formation of the charge gap in LaMnPO. Instead, density functional theory plus dynamical mean field theory calculations show that Hund's coupling is critical for the formation of the charge gap in LaMnPO, as well as related square net Mn pnictide compounds such as BaMn2As2 [D.E. McNally et al. PRB 92 115142 (2015)]. I will show that this work supports the view that multi-orbital electronic correlations are important in the isostructural iron pnictide based superconductors. 2. I present my inelastic neutron scattering measurements on single crystals of the antiferromagnetic insulator CaMn2Sb2, that forms a corrugated honeycomb lattice of Mn spins that order below TN = 85 K, rather low for a Mn pnictide compound. I observed sharp dispersive 3D spin wave excitations up to energy transfers of 25 meV. I used a Heisenberg model to analyze the excitations and determine the first, second and c-axis exchange interactions J1, J2, Jc. I use the determined ratio J2/J1 = 0.17 to situate CaMn2Sb2 on the theoretical phase diagram of the ho
-
ATLAS/HET Joint Lunch Seminar
"Constraints on New Physics via Higgs Boson Couplings and Invisible Decays with the ATLAS Detector"
Presented by Ketevi Assamagan, Brookhaven National Laboratory
Friday, September 25, 2015, 12 pm
Building 510 Room 2-160Hosted by: Amarjit Soni
The ATLAS experiment at the LHC has measured the Higgs boson couplings and mass, and searched for invisible Higgs boson decays, using multiple production and decay channels with up to 4.7 fb$^{-1}$ of $pp$ collision data at $\sqrt{s}=7$ TeV and 20.3 fb$^{-1}$ at $\sqrt{s}=8$ TeV. In the current study, the measured production and decay rates of the observed Higgs boson in the $\gamma\gamma$, $ZZ$, $WW$, $Z\gamma$, $bb$, $\tau\tau$, and $\mu\mu$ decay channels, along with results from the associated production of a Higgs boson with a top-quark pair, are used to probe the scaling of the couplings with mass. Limits are set on parameters in extensions of the Standard Model including a composite Higgs boson, an additional electroweak singlet, and two-Higgs-doublet models. Together with the measured mass of the scalar Higgs boson in the $\gamma\gamma$ and $ZZ$ decay modes, a lower limit is set on the pseudoscalar Higgs boson mass of $m_{A}>370$ GeV in the ``hMSSM'' simplified Minimal Supersymmetric Standard Model. Results from direct searches for heavy Higgs bosons are also interpreted in the hMSSM. Direct searches for invisible Higgs boson decays in the vector-boson fusion and associated production of a Higgs boson with $W/Z$ ($Z\to ll$, $W/Z \to jj$) modes are statistically combined to set an upper limit on the Higgs boson invisible branching ratio of 0.25. The use of the measured visible decay rates in a more general coupling fit improves the upper limit to 0.23, constraining a Higgs portal model of dark matter.
-
Condensed-Matter Physics & Materials Science Seminar
"Single-atom Impurity Effects in Iron-based Superconductors"
Presented by Shuheng H. Pan, Institute of Physics, Chinese Academy of Sciences
Friday, September 25, 2015, 11 am
ISB Bldg. 734, Conf. Rm. 201 (upstairs)Hosted by: Yimei Zhu
Impurities can break Cooper-pairs into quasi-particles with energy states inside the superconducting gap. The characteristics of such in-gap states reflect accordingly the properties of the superconducting ground state. Therefore, impurity effects in superconductors have always been important subjects in the fundamental study of superconductivity. A single-atom impurity is an ideal model for both experimental and theoretical study of impurity effects on superconductivity. With high resolution STM/S technique, such proposal has been successfully realized. In this talk, I will present some of our high resolution STM/S studies of single-atom impurity effects in iron-based superconductors and discuss their implications to the microscopic mechanism of iron-based superconductivity.
-
Particle Physics Seminar
"Time Delay Cosmology"
Presented by Eric Linder, Berkeley/LBNL
Thursday, September 24, 2015, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Anze Slosar
Thousands of strong gravitational lenses will be found by time domain surveys such as DES and LSST. Time delays between multiple images can be used to form a geometric time delay distance, a cosmological probe with some unique sensitivities and complementarities. I consider three aspects: 1) the cosmology impact, 2) the statistics challenge of accurate estimation of time delays between noisy, gappy lightcurves and recent results from LSST's blind Time Delay Challenge, and 3) optimization of limited followup resources. I will also present new theory and instrument concepts for cosmic redshift drift, a direct probe of cosmic acceleration with a Hubble time delay. Methods for both probes have interesting overlaps with exoplanet searches.
-
Condensed-Matter Physics & Materials Science Seminar
"A Giant Phonon Anomaly associated with Superconducting Fluctuations in the Pseudogap Phase of Cuprates"
Presented by Yehua Liu, ETH, Switzerland
Thursday, September 24, 2015, 1:30 pm
Bldg 734, 2nd Fl Conference RoomHosted by: Robert Konik
Recent observations of a Giant Phonon Anomaly at the onset of the pseudogap, has revealed another surprising property of this phase. The opening of the pseudogap in underdoped cuprates breaks up the Fermi surface, which in turn can cause a breakup of the superconducting d-wave order parameter into two subband amplitudes and to a low energy Leggett mode due to phase fluctuations between them. This leads to a large increase in the temperature range of superconducting fluctuations due to an overdamped Leggett mode. Almost resonant scattering of intersubband phonons to a state with a pair of Leggett modes, causes anomalously strong phonon damping. In the ordered state, the Leggett mode develops a finite energy, suppressing the anomalous phonon damping but leading to an anomaly in the phonon dispersion.
-
Nuclear Theory/RIKEN Seminar
"Single inclusive particle production at NLO: revised and improved"
Presented by Alex Kovner, University of Connecticut
Friday, September 18, 2015, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Soeren Schlichting
We discuss the recent improvement of the NLO calculation of single inclusive particle production in pA collisions within the CGC formalizm. The two points that have not been addressed previously, and are treated consistently in the current approach are the Ioffe time cutoff on the configurations that can participate in the scattering, and the careful treatment of the evolution interval.
-
Particle Physics Seminar
"CMB Constraints DM Annihilation/Sum of the neutrino masses from CMB observations"
Presented by Neelima Sehgal, Stony Brook University
Thursday, September 17, 2015, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Ketevi Assamagan
I will present the latest constraints on the properties of annihilating dark matter and on the sum of the neutrino masses from CMB observations. I will focus on what has been learned so far from the Planck satellite and current ground-based CMB experiments. I will also discuss what we can expect in the future in terms of constraining dark matter and neutrino properties from near-future ground-based experiments, such as Advanced ACTPol, and the planned DOE CMB-S4 project.
-
Condensed-Matter Physics & Materials Science Seminar
"Atomic spin chain realization of a model for quantum criticality"
Presented by Rianne van den Berg, Universiteit van Amsterdam, Netherlands
Thursday, September 17, 2015, 1:30 pm
Bldg 734, 2nd Fl Conference RoomHosted by: Robert Konik
The ability to manipulate single atoms has opened up the door to constructing interesting and useful quantum structures from the ground up. On the one hand, nanoscale arrangements of magnetic atoms are at the heart of future quantum computing and spintronic devices; on the other hand, they can be used as fundamental building blocks for the realization of textbook many-body quantum models, illustrating key concepts such as quantum phase transitions, topological order or frustration. Step-by-step assembly promises an interesting handle on the emergence of quantum collective behavior as one goes from one, to few, to many constituents. To achieve this, one must however maintain the ability to tune and measure local properties as the system size increases. We use low-temperature scanning tunneling microscopy to construct arrays of magnetic atoms on a surface, designed to behave like spin-1/2 XXZ Heisenberg chains in a transverse field, for which a quantum phase transition from an antiferromagnetic to a paramagnetic phase is predicted in the thermodynamic limit. Site-resolved measurements on these finite size realizations reveal a number of sudden ground state changes when the field approaches the critical value, each corresponding to a new domain wall entering the chains. We observe that these state crossings become closer for longer chains, indicating the onset of critical behavior. Our results present opportunities for further studies on quantum behavior of many- body systems, as a function of their size and structural complexity.
-
C-AD Accelerator Physics Seminar
"Attainment of Electron Beam Suitable for Medium Energy Electron Cooling"
Presented by Dr. Sergei Seletskiy, BNL-Photon Science
Thursday, September 17, 2015, 11 am
Bldg 911B, Large Conf. Rm., Rm A202""The Recycler Electron Cooler (REC) at Fermilab advanced the electron cooling to the MeV-range energies. The REC performance depended critically on the quality of electron beam. In my presentation I will describe various aspects of development of the REC and the techniques used to obtain the electron beam suitable for the cooling process."
-
Center for Functional Nanomaterials Seminar
"Fluctuation Electron Microscopy â€" probing higher order structural correlations in disordered materials by coherent diffraction Soft Matter Enhanced Electrochemical Energy Storage and 3D Photonic Crystals"
Presented by J. Murray Gibson, Department of Physics, Northeastern University, Boston
Thursday, September 10, 2015, 11 am
CFN, Building 735, 2nd floor - Seminar Conf. Rm.Hosted by: Eric Stach
Center for Functional Nanomaterials J. Murray Gibson Department of Physics, Northeastern University, Boston Fluctuation Electron Microscopy â€" probing higher order structural correlations in disordered materials by coherent diffraction Soft Matter Enhanced Electrochemical Energy Storage and 3D Photonic Crystals Thursday, September 10, 2015 11:00 a.m. Seminar Room, 2nd Fl. The conventional pair-correlation function, measured directly from diffraction, is a powerful tool to measure short-range order on the scale of chemical bonds and next neighbors. With sufficiently well-defined long range order, the 2-body function clearly reveals symmetry and periodicity. Diffraction techniques have thus been incredibly successful at the short-range in teaching us about the structure of liquids and amorphous solids, and at the other scale most of what we know about the crystalline structure of matter. However the 2-body function has a potential "blind spot" for ordering at intermediate length scales, typically up to of order ten bond lengths. Studies of amorphous materials by other techniques suggest that there can be pronounced medium-range ordering on the nanoscale and that it can significantly affect physical properties. It is now recognized that higher-order correlation functions (3 and 4 body) are far more sensitive to medium-range order and that that they can be accessed experimentally from coherent diffraction experiments. One of the earliest techniques to examine this was fluctuation microscopy (FM), developed by Treacy and Gibson1 for electron microscopy (FEM) and applied early to demonstrate medium-range order and the effect of annealing in amorphous germanium2. In more recent years, with the freer access to coherent sources of electrons and x-rays, more people are using FEM and developing related techniq
-
C-AD Accelerator Physics Seminar
"Multipass Energy Recovery Experiment at Jefferson Lab's CEBAF"
Presented by Dr. Todd Satogata, JLAB
Wednesday, September 9, 2015, 4 pm
Bldg. 911A, Snyder Seminar Room"The CEBAF recirculating linac accelerator has recently completed 12 GeV upgrade development, and plans to commission full energy accelerator setup this fall. With upgrade commissioning nearly complete, there is a new collaboration between BNL and Jefferson Lab that is developing a proposal for a multi-pass energy recovery experiment. This talk summarizes the current state of 12 GeV CEBAF, technical challenges for multi-pass energy recovery, and collaboration goals and technical progress for this multi-pass energy recovery experiment."
-
Joint Nuclear Physics and Particle Physics Seminar
"Understanding the nature of neutrinos via neutrinoless double-beta decay"
Presented by Wenqin Xu, Los Alamos National Laboratory
Tuesday, September 8, 2015, 11 am
Small Seminar Room, Bldg. 510Hosted by: Jin Huang
Neutrinos provide a critical portal to physics beyond the Standard Model, yet the nature of neutrinos is largely unknown, including the neutrino mass hierarcy and if neutrinos are Majorana particles. Majorana particles are fermions that are their own antiparticles. Neutrinos being Majorana particles would explicitly violate lepton number conservation, and would pave the way to understand the matter-antimatter asymmetry in the universe. Neutrinoless double-beta (0) decay is a hypothesized process where two neutrons decay into two protons and two electrons simultaneously without emitting neutrinos. It is possible only if neutrinos are Majorana particles, and it is the only feasible way to experimentally establish the Majorana or Dirac nature of neutrinos. The observation of 0 decay would also provide complementary information related to neutrino masses. After decades of experimental e orts, the next generation 0 decay experiments will have a signicant discovery potential to observe 0 decay, if neutrinos are indeed Majorana particles. In this talk, we will discuss the physics of neutrinoless double beta decay and review the experiments searching for it. We will focus on the Majorana Demonstrator, a 40-kg modular Germanium detector array, which searches for 0 decay in 76Ge and aims at demonstrating a path forward to next generation 0 decay experiments.
-
Nuclear Theory/RIKEN Seminar
"Asymptotic freedom of gluons in the Fock space"
Presented by Stanislaw Glazek, University of Warsaw
Friday, September 4, 2015, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Soeren Schlichting
Asymptotic freedom of gluons is defined in terms of scale-dependent renormalized QCD Hamiltonian operators that act in the Fock space. These operators are calculable in a new way [1,2], by solving a double-commutator differential equation [3], where the derivative is with respect to a scale parameter defined within the renormalization group procedure for effective particles (RGPEP). The RGPEP equation and its solutions are invariant with respect to boosts and may serve as a tool in attempts to dynamically explain the parton and constituent models of hadrons in QCD. The third-order QCD solution of the RGPEP equation to be discussed [2], provides an explicit example of how asymptotic freedom of gluons is exhibited in the scale-dependence of Hamiltonians as operators in the Fock space. This example also prepares ground for the fourth-order calculations of effective strong interactions using the same RGPEP equation [3], to facilitate Hamiltonian studies of many strong-interaction processes, e.g., those that involve heavy quarkonia in relativistic motion. Applications to other sectors of the Standard Model than the strong interactions await development, while only preliminary results are currently available in the domain of precise calculations in QED[4]. [1] Dynamics of effective gluons, S. D. Glazek, Phys. Rev. D63, 116006, 29p (2001). [2] Asymptotic freedom in the front-form Hamiltonian for gluons, M. Gomez-Rocha, S. D. Glazek, arXiv:1505.06688 [hep-ph], to appear in Phys. Rev. D. [3] Perturbative formulae for relativistic interactions of effective particles, S. D. Glazek, Acta Phys. Pol. B43, 1843, 20p (2012). [4] Calculation of size for bound-state constituent
-
RIKEN Lunch Seminar
"Analytic solution of the Boltzmann equation in the early universe"
Presented by Jorge Noronha, University of Sao Paulo
Thursday, September 3, 2015, 12:30 pm
Building 510 Room 2-160Hosted by: Daniel Pitonyak
A general method for exactly computing the nonlinear collision term of the Boltzmann equation for a massless relativistic gas in a homogeneous and isotropic spacetime is presented. This approach is used to find an exact analytical solution of the nonlinear relativistic Boltzmann equation in a Friedmann-Robertson-Walker spacetime. This solution can be used to investigate analytically the interplay between global expansion and local thermalization in rapidly evolving systems.
-
Nuclear Physics Seminar
"Orbital angular momentum and generalized transverse momentum distribution"
Presented by Mr. Yong Zhao, University of Maryland
Tuesday, August 25, 2015, 11 am
Small Seminar Room, Bldg. 510Hosted by: Oleg Eyser
Recent advances in theory have shown that it is possible to directly calculate the canonical quark and gluon orbital angular momentum contributions to the proton spin in lattice QCD. When boosted to the infinite momentum frame, the quark and gluon orbital angular momentum operators defined in the gauge-invariant nucleon spin sum rule of X. S. Chen et al. are the same as those derived from generalized transverse momentum distributions. The latter reduce to the canonical orbital angular momenta in the light-cone gauge, and can be measured in high-energy scattering experiments. I will show that these orbital angular momentum operators can be defined locally, and discuss the strategies of calculating their matrix elements in lattice QCD.
-
Special Nuclear Theory/RIKEN seminar
"Thermodynamics and topology from lattice QCD"
Presented by Michael Muller-Preussker, Humboldt University Berlin
Monday, August 24, 2015, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Soeren Schlichting
Recent efforts to investigate the thermodynamics of lattice QCD with N_f=2+1+1 fermion degrees of freedom at realistic strange and charm quark masses and at various up and down quark mass values within the framework of Wilson twisted mass fermion discretization are discussed. Comparing with recently published results in the N_f=2 case we are going to present results for the pseudo-critical temperature and preliminary results on the way to the thermodynamic equation of state. Moreover, we would like to discuss various methods to determine the topological susceptibility as a function of the temperature.
-
Center for Functional Nanomaterials Seminar
"Caught in the Act! Live Observations of Catalysts Using High-pressure Scanning Probe Microscopy"
Presented by Irene M. N. Groot, Leiden Institute of Physics and Leiden Institute of Chemistry, the Netherlands
Friday, August 21, 2015, 10 am
CFN, Bldg. 735, first fl. conference room AHosted by: Anibal Boscoboinik
Center for Functional Nanomaterials Seminar Caught in the Act! Live Observations of Catalysts Using High-pressure Scanning Probe Microscopy Irene M. N. Groot Leiden Institute of Physics and Leiden Institute of Chemistry, the Netherlands Friday, August 21, 2015 10:00 am Bldg. 735 â€" Conf. Rm. A Recently it has become clear that essential differences can exist between the behavior of catalysts under industrial conditions (high pressure and temperature) and the (ultra) high vacuum conditions of traditional laboratory experiments. Differences in structure, composition, reaction mechanism, activity, and selectivity have been observed. These observations indicated the presence of the so-called pressure gap, and made it clear that meaningful results can only be obtained at high pressures and temperatures. However, most of the techniques traditionally used to study catalysts and their reactions were designed to operate under (ultra) high vacuum conditions. To bridge the pressure gap, the last years have seen a tremendous effort in designing new instruments and adapting existing ones to be able to investigate catalysts in situ under industrially relevant conditions. This talk focuses on the development of scanning probe microscopy for operando observations of active model catalysts. In our group, we have developed set-ups that combine an ultrahigh vacuum environment for model catalyst preparation and characterization with a high-pressure flow reactor cell, integrated with either a scanning tunneling microscope or an atomic force microscope. With these set-ups we are able to perform atomic-scale investigations of well-defined model catalysts under industrial conditions. Additionally, we combine the structural information from scanning probe microscopy with time-resolved mass spectrometry measurements on the gas mixture that leaves the re
-
Particle Physics Seminar
"New Optical Techniques for Studying Vacuum Birefringence"
Presented by Carol Y. Scarlett, Florida A&M University
Thursday, August 20, 2015, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Elizabeth Worcester
The search for Axions, a particle theorized to explain the lack of CP violation in strong physics and suspected to contribute if not explain galactic dark matter, has lead to ever-sensitive techniques to study induced vacuum birefringence. What remains an issue: many of the measurable parameters that could give evidence for this illusive particle scale with the square of the birefringent angle (proportional to the photon-axion coupling constant). This talk will look at new techniques that can generate measurables that scale linearly (first order) with an induced birefringence. This has the potential to extend significantly the range through which cavity experiments can probe the vacuum of space in performing searches for axions and other exotic particles.
-
Computational Science Center Seminar
"High Performance Spatial Queries and Analytics for Spatial Big Data"
Presented by Fusheng Wang, SUNY SB
Tuesday, August 18, 2015, 10:30 am
John Dunn Seminar Room, Bldg. 463Support of high performance queries and analytics on large volumes of spatial data becomes increasingly important in many application domains, including geospatial problems and emerging scientific applications such as pathology imaging. There are two major challenges for managing and querying massive spatial data: the explosion of spatial data, and the high computational complexity of spatial queries due to its multi-dimensional nature. Our goal is to develop a general framework to support high performance spatial queries and analytics for spatial big data on MapReduce and CPU-GPU hybrid platforms. In this talk, I will present a scalable and high performance spatial data warehousing system Hadoop-GIS for running large scale spatial queries on Hadoop and Spark. Hadoop-GIS achieves scalable and efficient queries through optimized spatial partitioning, multi-level indexing, customizable spatial query engine RESQUE and implicit parallel spatial query execution. I will introduce applications of the system to support pathology imaging analytics and social media analytics.
-
Nuclear Theory/RIKEN Seminar
"Initial state correlations, entanglement entropy and all that"
Presented by Michal Lublinsky, Ben Gurion University of the Negev
Friday, August 14, 2015, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Soeren Schlichting
I will discuss high energy collisions of dilute on dense systems (pA) and review some ideas about initial-state induced correlations.
-
Particle Physics Seminar
"Exciting New Results From LHCb"
Presented by Sheldon Stone, Syracuse University
Thursday, August 13, 2015, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Elizabeth Worchester
LHCb has presented groundbreaking new results this summer in exotic particle spectroscopy and searches for new physics.
-
RIKEN Lunch Seminar
"Discrimination of large quantum ensembles"
Presented by Emilio Bagan, GIQ, Physics Dept., UAB, Spain and Hunter College of the CUNY
Thursday, August 13, 2015, 12:30 pm
Building 510, Room 2-160Hosted by: Daniel Pitonyak
"Hypothesis testing is arguably the most common and elementary task in information processing (e.g., we constantly make decisions based on incomplete information). Its quantum version, quantum state discrimination, is likewise central in quantum information processing. The talk gives an introduction to the topic, focussing on discrimination of a large amount of identically prepared systems. In this limit, a powerful bound on the error rate can be derived. In classical statistics this is know as Chernoff bound. The quantum version of the Chernoff bound will be presented and discussed."
-
Physics Colloquium
"Life after Physics: A look back on 20 years in Finance"
Presented by Andreas Gocksch
Tuesday, August 11, 2015, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Robert Pisarski
After 10 years of research in High Energy Theory this BNL graduate ('83-'85 and '88-'93) followed the call of Wall Street. In my talk I reflect on over 20 years in the financial industry with an emphasis on highlighting possible career choices for young people that might one day be faced with searching for a "life after Physics". Along the way I also hope to leave the audience with an understanding of some basic facts about Finance and an appreciation for the utility of the physicist's toolkit in the "real world". *This talk may be of especial interest to students.
-
HET/RIKEN seminar
"Higgs coupling deviations, vacuum stability and new bosons at the TeV scale"
Presented by Raffaele D'Agnolo, Institute for Advanced Study
Wednesday, August 5, 2015, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Chien-Yi Chen
Higgs coupling measurements can shed light on the nature of electroweak symmetry breaking. However it is not trivial to go beyond generic intuitions, such as the expectation that natural theories generate large deviations, and make precise statements. In this talk I will show in a model independent way that measuring deviations at the LHC implies the existence of new bosons between a few TeV and a few hundred TeV. This is true in general, including theories where new fermions produce the deviations.
-
Nuclear Theory/RIKEN seminar
"Generalized Landau-level representation for spin-1/2 fermions and its applications"
Presented by Igor Shovkovy, Arizona State University
Friday, July 31, 2015, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Soeren Schlichting
I will discuss the recently proposed generalized Landau-level representation for charged fermions in an external magnetic field. After demonstrating its key advantages over the other existing representations, I will mention several of its applications. One of them is the quantum Hall effect in graphene, where the new representation is essential for a sufficiently detailed theoretical description, in which all the dynamical parameters are running functions of the Landau-level index. The other application is the chiral asymmetry induced in dense relativistic matter in an external magnetic field. The quantitative measure of such an asymmetry is the chiral shift parameter that measures a relative shift of the longitudinal momenta (along the direction of the magnetic field) in the dispersion relations of opposite chirality fermions. Using the language of solid state physics, the corresponding ground state of dense relativistic matter could be interpreted as a Weyl metal state. Incidentally, the exact same mechanism also works in real Dirac metals.
-
C-AD Accelerator Physics Seminar
"Muon Accelerators: R&D Towards Future Neutrino Factory and Lepton Collider Capabilities"
Presented by Mark Palmer, Fermilab
Thursday, July 30, 2015, 3:30 pm
Building 911B, Large Conference Room, Second FloorThis talk will describe the evolution of Muon accelerator R&D. An overview of what has been accomplished under the U.S. Muon Accelerator Program (MAP), what remains to be done, and how the elements of the program are evolving will be presented.
-
RIKEN Lunch Seminar
"P-odd Spectral Density at Weak Coupling: Photon Emission and Second"
Presented by Ho-Ung Yee, University of Illinois at Chicago
Thursday, July 30, 2015, 12:30 pm
Building 510 Room 2-160Hosted by: Daniel Pitonyak
The P-odd spectral density of current correlation functions appears in several physical observables which are related to chiral anomaly, and is a sensitive probe of microscopic dynamics which is less protected by symmetry alone. We discuss two examples of their appearance: photon emission and the second order transport coefficient from chiral anomaly. We describe leading order weak coupling computations for these examples.
-
Physics Colloquium
"Exotic and conventional hadrons from lattice QCD"
Presented by Sasa Prelovsek, University of Ljubljana, Jefferson Lab
Tuesday, July 28, 2015, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Rob Pisarski
Faced with the recent experimental discoveries of pentaquarks and tetraquarks, one would like to establish whether these states arise directly from the fundamental theory of strong interactions - QCD. I will present how the exotic and conventional hadrons are investigated with ab-initio lattice QCD simulations. The approach will be illustrated with recent lattice results on the charmonium-like states Zc and X(3872), conventional resonances, bound states and pentaquarks.
-
Nuclear Theory/RIKEN seminar
"Resumming large radiative corrections in the high-energy evolution of the Color Glass Condensate"
Presented by Edmond Iancu, CEA Saclay
Friday, July 24, 2015, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Speren Schlichting
The BK-JIMWLK equations describing the evolution of the Color Glass Condensate with increasing energy have recently been extended to next-to-leading order (NLO) accuracy. However, some of the NLO corrections turn out to be extremely large, since amplified by (double and single) `collinear' logarithms, i.e. logarithms of ratios of transverse momenta. This difficulty points towards the existence of large radiative corrections to all orders in $\alpha_s$, as generated by the transverse phase-space, which must be computed and resummed in order to restore the convergence of the perturbative expansion. In a couple of recent papers, we developed a resummation scheme in that sense, which achieves a complete resummation of the double-logarithmic corrections and a partial resummation of the single-logarithmic ones (including the running coupling effects). We have thus deduced a collinearly-improved version of the BK equation which includes the largest radiative corrections to all orders. To demonstrate the usefulness of this equation as a tool for phenomenology, for have used it for fits to the HERA data for electron-proton deep inelastic scattering at high energy. We have obtained excellent fits with a reduced number of free parameters and with initial conditions at low energy taken from perturbative QCD.
-
High Energy Physics Seminar
"New results from the hydrogen channel in Double Chooz"
Presented by Rachel Carr, Columbia University
Thursday, July 23, 2015, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Elizabeth Worcester
Beginning in 2011, the Double Chooz experiment has produced increasingly precise measurements of the neutrino oscillation parameter sin22θ13. These measurements rely on the detection of reactor antineutrinos through the inverse beta decay (IBD) interaction. The most recent analysis uses IBD interactions followed by neutron capture on hydrogen, rather than the standard Gd capture channel. A new artificial neural network-based signal selection, novel background rejection techniques, and reduced detection systematics make this analysis far more sensitive than the original H-channel measurement in Double Chooz. The precision of this new sin22θ13 measurement approaches that of the Gd-channel measurement, demonstrating the possibility of performing high-sensitivity physics measurements without a Gd dopant.
-
Condensed-Matter Physics & Materials Science Seminar
"Discovery of Weyl fermions in condensed matter"
Presented by Hong Ding, Inst. of Physics, Chinese Academy of Sciences, China
Wednesday, July 22, 2015, 1:30 pm
Bldg. 734, ISB Conf. Room 201 (upstairs)Hosted by: Peter D. Johnson
In 1929, a German mathematician and physicist Hermann Weyl proposed that a massless solution of the Dirac equation represents a pair of new type of particles, the so-called Weyl fermions. However, their existence in particle physics remains elusive after more than eight decades, e.g., neutrino has been regarded as a Weyl fermion in the Standard Model until it was found to have mass. Recently, significant advances in both topological insulators and topological semimetals have provided an alternative way to realize Weyl fermions in condensed matter as an emergent phenomenon. Weyl semimetals are predicted as a class of topological materials that can be regarded as three-dimensional analogs of graphene breaking time reversal or inversion symmetry. Electrons in a Weyl semimetal behave exactly as Weyl fermions, which have many exotic properties, such as chiral anomaly, magnetic monopoles in the crystal momentum space, and open Fermi arcs on the surface. In this talk I will report our discovery of a Weyl semimetal in TaAs by observing Fermi arcs in the surface states and Weyl nodes in the bulk states using angle-resolved photoemission spectroscopy.
-
C-AD Accelerator Physics Seminar
""A Holistic Approach to Accelerator Reliability Modeling""
Presented by Miha Rescic, University of Huddersfield
Wednesday, July 22, 2015, 1:30 pm
Bldg 911B, Large Conf. Rm. Rm A202Hosted by: Steve Peggs/Kevin Brown
"High reliability has become a crucial issue in the design and operation of accelerators due to the demands of specific applications (e.g. medical accelerators, neutron spallation sources, nuclear waste transmutation). This is particularly relevant for accelerator-driven neutron facilities and for Accelerator-Driven Systems technologies for waste transmutation. Until now, accelerator reliability analysis has mostly been performed using simplified methods either in the design phase of projects, or after the accelerator is operational. This talk discusses a holistic approach to accelerator reliability modeling using Hidden Markov Models to look for emergent behavior of the accelerator, using system-complexity agnostics datasets from the operating machine, e.g. beam current or charge."
-
Condensed-Matter Physics & Materials Science Seminar
"Imaging and Understanding Atomic-Scale Surface Interactions: Quantitative Investigations Using In Situ Electron Microscopy"
Presented by Prof. Tevis Jacobs, University of Pittsburgh
Monday, July 20, 2015, 1:30 pm
Conference Room, Building 480Hosted by: Myung-Geun Han
The atomic-scale mechanisms that govern the adhesion, mechanical deformation, and bonding of surfaces in contact are not well understood. Yet accurate description and prediction of such contact phenomena is critically important in advanced nanoscale applications, including scanning probe microscopy (e.g., nanoscale mapping of mechanical and functional properties), micro-/nano-electromechanical systems (e.g., actuators, switches), and nanomanufacturing processes (e.g., scanning probe lithography). In this talk, I will discuss contact and sliding tests on nanoscale tips of silicon and other technologically relevant materials. These tests were performed inside of a transmission electron microscope (TEM), enabling in situ interrogation of a contact interface while controlling the displacement of the bodies and measuring normal forces with sub-nanonewton resolution. Quantitative data were extracted using custom analysis routines to resolve the geometry of the contacting bodies, adhesive forces, and volumes removed due to sliding wear, all with unprecedented resolution. In the first part of the talk, TEM adhesion tests of carbon-based coatings on diamond performed using this setup will be discussed. Sub-nanonewton force resolution was paired with Angstrom-scale measurements of asperity geometry. Combined with complementary molecular dynamics simulations, these results revealed an order-of-magnitude reduction in apparent work of adhesion as tip roughness increased from atomic-scale corrugation to a root-mean-square value of 1 nm. These results demonstrate the strong effect of sub-nanoscale topography on adhesion, and highlight a key limitation of conventional approaches for measuring the work of adhesion. In the second part of the talk, in situ sliding tests of silicon tips sliding on diamond at low applied loads reveal that wear occurs by atomic attrition: gradual material removal at the atomic scale. The process can be accurately described using stress
-
Nuclear Theory/RIKEN seminar
"The LPM effect in energy loss and sequential bremsstrahlung"
Presented by Peter Arnold, University of Virginia
Friday, July 17, 2015, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Soeren Schlichting
High-energy particles passing through matter lose energy by showering via hard bremsstrahlung and pair production. At very high energy, the quantum duration of each splitting process, known as the formation time, exceeds the mean free time for collisions with the medium, leading to a significant reduction in the splitting rate, known as the Landau-Pomeranchuk-Migdal (LPM) effect. A long-standing problem in field theory has been to understand how to implement this effect in cases where the formation times of two consecutive splittings overlap. I will review why this question is interesting and discuss recent progress in the context of jet energy loss in quark-gluon plasmas.
-
Instrumentation Division Seminar
"Design of specific high speed converters at LPSC Grenoble"
Presented by Daniel Dzahini, Laboratory of Subatomic Physics and Cosmology, Grenoble, France
Wednesday, July 15, 2015, 2:30 pm
Large Conference Room, Bldg. 535This presentation will describe the design of specific high speed and high resolution converters in LPSC Grenoble. ADC designs for calorimeters and different pixels detectors will be discussed in detail. Trends and constraints for future converter designs in DSM process will also be described.
-
Condensed-Matter Physics & Materials Science Seminar
"Revisiting Josephson junction phase dynamics and its codes"
Presented by Francesco Tafuri, Seconda Università di Napoli & CNR-SPIN, Unità di Napoli, Italy
Monday, July 13, 2015, 1:30 pm
Bldg. 480 Conference RoomHosted by: Ivan Bozovic
The Josephson effect is still a unique key towards a variety of frontier problems ranging from the detection of Majorana fermions to macroscopic quantum phenomena and qubit applications. Progress in material science in producing a larger variety of interfaces and in nanotechnologies applied to superconductivity, may promote a renewal on the paradigms of the phase dynamics of Josephson junctions with relevant consequences on a series of key issues. We will discuss some relevant experiments mostly realized on unconventional junctions, including hybrid devices, nano-junctions, and especially high critical temperature superconductors (HTS). Novel phenomena emerge because of the possibility of driving materials and junctions with an accurate control in unexplored regimes. We have investigated different micro-structural configurations, which offer a wide range of junction dynamical parameters. A transition from classical Josephson phase dynamics, which takes place in junctions characterized by low values of critical current density Jc, to a regime in which dissipation is driven by local heating processes, for high values of Jc. We demonstrate how non-equilibrium effects and local processes in constrained geometry are codified in the response of the junctions and can be disentangled from other effects. Escape dynamics turns as an active 'imaging' of nano-scale transport with an enormous potential and the ability of encoding subtle transport information in fluctuations. We speculate on possible intrinsic nanoscale ordering occurring in HTS systems. This transition is of relevance for all kinds of weak links including the emergent family of nano-hybrid junctions. Information on the search of quantum phase slips can be also derived. Experiments on reference systems as HTS nanowires and Josephson junctions with ferromagnetic spin-valve tunnel barriers (experiment made in collaboration with University of Cambridge) will be finally
-
C-AD Accelerator Physics Seminar
""Cascaded Longitudinal Space Charge Amplifier for Short-Wavelength Radiation Generation at Fermilab's ASTA""
Presented by Aliaksei Halavanau, Northern Illinois University
Friday, July 10, 2015, 11 am
Bldg 911B, Large Conf. Rm., Rm. A202"Longitudinal space charge (LSC) effects are generally considered as detrimental in free-electron lasers as they can seed unwanted energy modulations and emittance growth. There has however been an increasing interest in devising accelerator beam lines capable of sustaining this LSC instability as a mechanism to operate as a coherent light source. In such a cascaded longitudinal space charge amplifier (LSCA), initial noise present in the beam density is amplified via the interplay of longitudinal space charge forces and properly located dispersive sections. To date most of these studies have been carried out with a one-dimensional impedance model for the LSC. We use an available grid-less three-dimensional N-body ``Barnes-Hut'' algorithm to simulate the 3D space charge force in the beam combined with ELEGANT and explore the limitations of the 1D model often used. We investigate, via numerical simulations, the performances of a cascaded LSCA beam line at the Fermilab's Advanced Superconducting Test Accelerator (ASTA)."
-
Nuclear Physics Seminar
"In search of old and new anomalous chiral effects in heavy ion collisions"
Presented by Jinfeng Liao, Indiana University
Tuesday, June 30, 2015, 11 am
Small Seminar Room, Bldg. 510Hosted by: Oleg Eyser
The heavy ion collision provides a unique many-body environment where local domains of strongly interacting chiral medium may occur. Certain anomalous transport processes, forbidden in usual medium, become possible in such domains. These anomalous chiral effects have their microscopic origin at the fundamental quantum anomaly and manifest themselves macroscopically in hydrodynamic currents. In the first part of this talk we report our recent finding (arXiv:1504.03201) of a new gapless collective excitation, called the Chiral Vortical Wave (CVW) in a rotating quark-gluon plasma. The CVW wave equation will be derived, and we show that its solutions describe nontrivial CVW-induced charge transport. We further propose and estimate possible experimental signals. In the second part of this talk we report our state-of-the-art simulations of the long-sought-after Chiral Magnetic Effect (CME), performed in the anomalous hydrodynamic framework and taking into account identified background contributions (arXiV:1504.06906). We discuss the implications of our results for the experimental search of CME
-
Condensed-Matter Physics & Materials Science Seminar
"Microscopic engineering of complex oxide ground states"
Presented by Derek Meyers, University of Arkansas
Monday, June 29, 2015, 1:30 pm
ISB Bldg. 734, Conf. Rm. 201 (upstairs)Hosted by: Mark Dean
Transition metal oxides have come to the forefront of condensed matter research in the past several decades due to their highly diverse phase space and remarkable susceptibility to external tuning. This has lead to their prevalence in the pursuit of designer phases, i.e. room temperature superconductivity, topological phases, and etc. In this talk we explore several methods for engineering the ground state of these systems including "ordered doping", applied epitaxial strain, and superlattice heterostructuring in an effort to gain further insight into the microscopic origin of this tunability. We employ synchrotron based x-ray spectroscopy and resonant diffraction to elucidate the explicit origin of the observed anomalous behaviors. In particular, our results reveal the ability to mask the effects of spin-orbit coupling in heavier oxides and to suppress or enhance bulk phase transitions by design.
-
Nuclear Theory/RIKEN Seminar
"Event by Event fluctuations in pQCD + saturation + hydro model: pinning down QCD matter shear viscosity in AA collisions"
Presented by Risto Paatelainen, University of Jyvaskyla
Friday, June 26, 2015, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Soeren Schlichting
We introduce an event-by-event perturbative-QCD + saturation + hydro ("EKRT") framework for ultrarelativistic heavy-ion collisions, where we compute the produced fluctuating QCD-matter energy densities from next-to-leading order perturbative QCD using a saturation conjecture to control soft particle production, and describe the space-time evolution of the QCD matter with dissipative fluid dynamics, event by event. We perform a simultaneous comparison of the centrality dependence of hadronic multiplicities, transverse momentum spectra, and flow coefficients of the azimuth-angle asymmetries, against the LHC and RHIC measurements. We compare also the computed event-by-event probability distributions of relative fluctuations of elliptic flow, and event-plane angle correlations, with the experimental data from Pb+Pb collisions at the LHC. We show how such a systematic multi-energy and multi-observable analysis tests the initial state calculation and the applicability region of hydrodynamics, and in particular how it constrains the temperature dependence of the shear viscosity-to-entropy ratio of QCD matter in its different phases in a remarkably consistent manner.
-
RIKEN Lunch Seminar
"One-Flavor QCD and the Dirac Spectrum at $\theta=0$"
Presented by Jacobus Verbaarschot, Stony Brook University
Thursday, June 25, 2015, 12:30 pm
Building 510 Room 2-160Hosted by: Daniel Pitonyak
The chiral condensate of one-flavor QCD is continuous when the quark mass crosses zero. In the sector of fixed topological charge though, the chiral condensate becomes discontinuous at zero mass in the the thermodynamical limit. To reconcile these contradictory observations, we have evaluated the spectral density of the Dirac operator in the epsilon domain of one-flavor QCD. In this domain, we have obtained exact analytical expressions which show that the spectral density at $\theta = 0$ becomes a strongly oscillating function for negative quark mass with an amplitude that increases exponentially with the volume. As is the case for QCD at nonzero chemical potential, these strong oscillations invalidate the Banks-Casher formula and result in a chiral condensate that is continuous as a function of the quark mass. An additional subtlety is the effect of the topological zero modes which will be discussed as well.
-
Nuclear Theory/RIKEN seminar
"Jet angular broadening in Heavy-Ion collisions"
Presented by Yacine Mehtar-Tani, University of Washington
Friday, June 19, 2015, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Soeren Schlichting
The advent of the LHC opened up new perspectives for jet-quenching physics. For the first time, high enough energies are reached in heavy-ion experiments to produced jets in large numbers, and the unprecedented detector capabilities of ALICE, ATLAS and CMS, not only extend the kinematic range for the measurements previously performed at RHIC, but also allow to explore a variety of new jet-quenching observables. In this talk, I address the question of the angular broadening of jets in the presence of a dense QCD matter. I start by discussing the fundamental mechanisms underlying the formation of gluon cascades induced by multiple interactions of high energy jets with the quark-gluon plasma. Then, the rate equation that describes the evolution of the energy and angular distribution of the in-medium gluon shower is presented and solved. Two remarkable phenomena emerge. First and foremost the energy spectrum (of jet constituents) exhibits a scaling behavior characterized by a constant flow of energy towards low momenta akin to wave turbulence. As a result, energy is rapidly transported from the energy containing partons to low momentum gluons before it dissipates into the medium. Second, medium-induced gluon cascades develop and transport energy at parametrically large angles with respect to the jet axis. This picture is in semi-quantitive agreement with a recent CMS analysis of the missing energy in asymmetric dijet events where the energy balance is recovered at large angles and very soft particles.
-
PubSci
"Big Bang Physics and the Building Blocks of Matter"
Thursday, June 18, 2015, 7 pm
The Bahche 191 7th St, Brooklyn, NY 11215Invite your friends and colleagues to a lively discussion for the science-interested (or just plain curious) and chat with scientists in an informal and friendly way. No stuffy lectures â€" just a dynamic talk with a diverse audience and a lot of good cheer. Physicists who work at Brookhaven's particle collider will talk about how they explore what happened at the dawn of time from a Lab on Long Island. How did the Universe take shape? What binds matter together? How do we answer those questions?
-
Particle Physics Seminar
"Detection of Lensing of the CMB by Dark Matter Halos"
Presented by Mathew S Madhavacheril, Stony Brook University
Thursday, June 18, 2015, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Morgan May
I will report on the first detection of lensing of the cosmic microwave background by dark matter halos. Halo lensing of the CMB provides a method for constraining cluster masses complementary to optical weak lensing, with the advantage that the source plane has a very well determined redshift and statistical properties. In this work, the lensing field was reconstructed from CMB temperature observations using the ACTPol telescope and stacked at the location of CMASS galaxies which trace dark matter halos of ~10^13 M_solar galaxy groups, providing a 3.2 sigma detection and a ~35% mass constraint. I will also briefly touch on the capabilities of future CMB experiments to use this method to constrain dark energy parameters.
-
RIKEN Lunch Seminar
"Self-similar evolution for inverse cascade of magnetic helicity driven by the chiral anomaly"
Presented by Yi Yin, Brookhaven National Laboratory
Thursday, June 18, 2015, 12:30 pm
Small Seminar Room, Bldg. 510Hosted by: Daniel Pitonyak
We show by solving Maxwell's equations in the presence of chiral magnetic current that the chiral anomaly would induce the inverse cascade of magnetic helicity. We found at late time, the evolution of magnetic helicity spectrum is self-similar and axial charge decays as a power law in time. We visualize how a linked magnetic configuration would evolve into a knotted configuration in real space during such evolution.
-
Particle Physics Seminar
"Constraining the Standard Model and new physics with LHC data"
Presented by Alessandro Tricoli, CERN
Friday, June 12, 2015, 11 am
Small Seminar Room, Bldg. 510Hosted by: Ketevi Assamagan
The Large Hadron Collider (LHC) project at CERN Laboratory in Geneva has achieved one of its primary goals, i.e. the discovery of the Higgs boson particle, which completes the Standard Model of particle physics. However, no signatures of new physics beyond the Standard Model have been observed yet, despite thorough searches. Nature turns out to be subtle. The direct search will continue in the upcoming LHC runs, however new physics can also be pursued indirectly by looking for deviations of experimental results from predictions in measurements of Standard Model processes. The LHC has provided a large data set during its first years of operations. This has been used to perform measurements of Standard Model processes that constrain predictions in the strong and electro-weak sectors and are sensitive to new physics in a model-independent way, thanks to the high level of precision and the extent of their kinematic reach. A good understanding of these processes is of paramount importance for precision Higgs physics, as well as for searches for new physics, as they constitute irreducible backgrounds. After presenting a selection of highlights of recent Standard Model measurements from the LHC, I will discuss how the precision and phase space reach of these measurements will improve in future LHC runs, given the increase of centre-of-mass energy and integrated luminosity, emphasising some of the experimental challenges ahead.
-
Particle Physics Seminar
"Search for dark sector particles at Belle and Belle II"
Presented by Igal Jaegle, University of Hawai`i at MÄnoa
Thursday, June 11, 2015, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Ketevi A. Assamagan
The dark photon, A′,, and the dark Higgs boson, h′, are hypothetical constituents featured in a number of recently proposed Dark Sector Models. We will present a search for these particles in the so-called Higgs-strahlung channel, e+eâˆ'â†'A′h′, with h′â†'A′A′. We investigated ten exclusive final-states with A′â†'e+eâˆ', μ+μâˆ', or Ï€+Ï€âˆ', in the mass ranges 0.1 GeV/c2 <mA′<3.5 GeV/c2 and 0.2 GeV/c2 <mh′<10.5 GeV/c2. We also investigated three inclusive final-states, 2(e+eâˆ')X, 2(μ+μâˆ')X, and (e+eâˆ')(μ+μâˆ')X, where X denotes a dark photon candidate detected via missing mass, in the mass ranges 1.1 GeV/c2 <mA′<3.5 GeV/c2 and 2.2 GeV/c2 <mh′<10.5 GeV/c2. Using the entire 977fbâˆ'1 data set collected by Belle, we observed no significant signal. We will also discuss prospects for searches for light dark matter and the dark photon in the radiative decay process at Belle and Belle II.
-
HET/RIKEN seminar
"New physics in b—>s transitions after LHC run 1"
Presented by Wolfgang Altmannshofer, Perimeter Institute
Wednesday, June 10, 2015, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Chien-Yi Chen
I will discuss interpretations of the recent updated angular analysis of the B->K*mu+mu- decay by the LHCb collaboration. A global fit to all relevant measurements probing the flavor changing neutral current b->s mu mu transition shows tensions with Standard Model expectations. Assuming hadronic uncertainties are estimated in a sufficiently conservative way, I will discuss the implications of the experimental results on new physics, both model independently as well as in the context of models with flavor changing Z' bosons.
-
Nuclear Theory/RIKEN seminar
"Novel mechanisms of charmonium suppression/enhancement in pA and AA collisions"
Presented by Boris Kopeliovich, Universidad Tecnica Federico Santa Maria, Valparaiso
Friday, June 5, 2015, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Soeren Schlichting
Charmonium production in pA collisions is known to be suppressed by shadowing and absorption. There are however nuclear effects, which enhance charmonium yield. They steeply rise with energy and seem to show up in LHC data for J/psi production in pA collisions. In the case of heavy ion collisions produced charmonia are additionally suppressed by final state interaction in the created dense medium. On the contrary to current evaluations of the melting effects caused by Debye screening, a charmonium produced with a large pT easily survives even at high temperatures. Another source of charmonium suppression, missed in previous calculations, color-exchange interactions with the medium, leads to suppression of a comparable magnitude. A quantitative comparison is performed.
-
Condensed-Matter Physics & Materials Science Seminar
"GGE and applications for integrable models"
Presented by Garry Goldstein, Rutgers University
Thursday, June 4, 2015, 4 pm
ISB 2nd floor seminar roomHosted by: Robert Konik
We consider quenches of integrable models. We derive a Yudson representation applicable to finite sized systems. Using this representation we find expressions for the time dependence of density density and related correlation functions for an arbitrary quench of the repulsive LiebLiniger gas. We use this to show that the GGE formalism is applicable to the long time limit for quenches of the Lieb-Liniger gas with sufficiently regular initial states. We then show that no similar GGE formalism applies to quenches for integrable models with bound states (such as the XXZ model or the Hubbard model). We study several specific examples of quenches, in particular quenches where the initial state is a Mott insulator or has low entropy. We find the exact quasiparticle density for such quenches and use it to study the long time limit of some correlation functions for the system. We also consider quenches of confined systems, in particular the Lieb-linger gas in a box. We show that the GGE formalism applies to the long time average of such quenches. We use this observation to compute the long time average quasiparticle density for some quenches similar to the Quantum Newton's cradle quench experiment. We also compute various correlation functions for the system in particular the probability distribution for the particle velocity.
-
Condensed-Matter Physics & Materials Science Seminar
"Band edge and photo induced superconductivity"
Presented by Garry Goldstein, Rutgers
Thursday, June 4, 2015, 1:30 pm
2nd Fl Lecture Room ISBHosted by: Robert Konik
We discuss novel routes to obtain superconductivity in semiconductors. We consider a semiconductor with a band dispersion where there is a band edge, such as semiconductors with Rashba spin-orbit coupling or bilayer graphene with a voltage between the layers. We find robust superconductivity, both p-wave and s-wave depending on the type of band edge, for semiconductors with attractive interactions (such as those caused by phonon exchange) when we tune the chemical potential close to the band edge. We also consider photo induced superconductivity in a two band semiconductor. We use optical pumping to induce nonequilibrium populations within the bands. We find robust superconductivity for appropriate chemical potential and dispersion relations for the bands. This s-wave superconductivity can be induced by both repulsive and attractive interactions depending on the exact band dispersions. Various band geometries are discussed.
-
Physics Colloquium
"Quarkonium with Effective field theories"
Presented by Nora Brambilla, Munich Technical University
Tuesday, June 2, 2015, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Peter Petreczky
Quantum Chromodynamics (QCD) is the sector of the Standard Model of particle physics that describes the strong interaction, deceptively simple to formulate but notoriously difficult to solve. Heavy quarkonium is a multiscale system that probes the different energy regimes of QCD, from the high-energy region, where an expansion in the coupling constant is possible and precision studies may be done, to the low-energy region, dominated by confinement and the many manifestations of the nonperturbative strong dynamics. Properties of production and absorption of quarkonium in a medium are also crucial for the study of QCD at high density and temperature. On the theoretical side, the construction of new nonrelativistic effective field theories for quarkonium has recently revolutionized the field providing both a conceptual framework and a powerful calculational tool. On the experimental side, the diversity, quantity and accuracy of the data collected in the last few years at B and tau-charm factories and at RHIC and LHC experiments is impressive, featuring the observation of new states and new unexpected processes. I will discuss these theoretical and experimental advancements and their implications for our understanding of strong interactions.
-
Nuclear Physics Seminar
"Elliptic flow from anisotropic escape"
Presented by Denes Molnar, Purdue University
Tuesday, June 2, 2015, 11 am
Small Seminar Room, Bldg. 510Hosted by: Jin Huang
While hydrodynamics is regarded as the dominant paradigm for describing heavy-ion collisions at RHIC and LHC energies, its applicability to nuclear reactions is not very well understood. Open question remain about the mechanism of rapid thermalization, initial conditions, treatment of decoupling (conversion of the fluid to particles), finite system effects, and quantum corrections in very small systems, for example. In a recent work (arXiv:1502.05572) we showed that in the AMPT transport model elliptic flow is generated quite differently from hydrodynamics, mainly through anisotropic escape from the collision zone. I will demonstrate that this is, in fact, a general feature of kinetic theory, originating in the modest opacities <Ncoll> \sim 4-5 in AMPT calculations. Implications of the escape effect will be discussed together with connections to other hydro related problems such as proper particle distributions (arXiv:1404.8750) and anisotropic flow from quantum mechanics (arXiv:1404.4119).
-
Particle Physics Seminar
"LHCb Run I Results and Run II Prospects"
Presented by Philip Ilten, Massachusetts Institute of Technology
Thursday, May 28, 2015, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Ketevi A. Assamagan
The LHCb detector is a forward arm spectrometer on the Large Hadron Collider, designed for the study of particles containing b or c quarks. A variety of recent results from the Run I dataset, taken from 2010 - 2013, will be presented, emphasizing the scope of the LHCb physics program. These areas include central exlusive production of quarkonia, exotic particle searches, precision electroweak cross-sections, CKM measurements, and more. Prospects for Run II measurements will be outlined.
-
Condensed-Matter Physics & Materials Science Seminar
"Transport properties of novel thermoelectric materials"
Presented by Hang Chi, Department of Physics, University of Michigan
Thursday, May 28, 2015, 11 am
Bldg.480 Conf. RmHosted by: Qiang Li
Thermoelectric materials can recover waste industrial heat and convert it to electricity as well as provide efficient local cooling of electronic devices. The efficiency (determined by the dimensionless figure-of-merit ZT) of such environmentally responsible and exceptionally reliable solid state energy conversion can be enhanced through (i) electronic band engineering (n-type Mg2Si-Mg2Sn solid solutions and p-type SnTe) and (ii) thermal conductivity reduction (Ge/Te double substituted CoSb3). Detailed transport and structure studies of Bi2Te3-based single crystals demonstrate that a bulk (semi-)insulating state for such a topological insulator can be achieved via group III (Tl or In) elemental doping, which opens an avenue for further investigations of transport phenomena related to surface states. Further systematic study in Bi2Te3-based molecular beam epitaxial (MBE) thin films grown on sapphire (0001) and/or BaF2 (111) substrates, reveal that the peak of phonon drag can be tuned by the choice of substrates with different Debye temperatures.
-
Nuclear Physics Seminar
"Probing Nucleon Structure Through Transversely Polarized Proton-proton Collisions at STAR"
Presented by Jim L. Drachenberg, Valparaiso University
Tuesday, May 26, 2015, 11 am
Small Seminar Room, Bldg. 510Hosted by: Oleg Eyser
At leading twist, a complete picture of the one-dimensional momentum structure of the nucleon requires knowledge of three types of parton distribution functions (PDFs): the unpolarized PDFs; the helicity PDFs; and the transversity PDF, related to the transverse polarization of quarks within a transversely polarized nucleon. Current global extractions of transversity are limited by the kinematic reach of existing semi-inclusive deep-inelastic scattering (SIDIS) experiments. Beyond the open questions of one-dimensional nucleon structure, myriad opportunities abound in exploring the multi-dimensional structure of the nucleon. A step toward this goal is to investigate the nature of the transverse momentum dependence (TMD) of nucleon parton densities and their relation to nucleon spin polarization. The STAR experiment at RHIC proposes to investigate these and other spin-related phenomena through the interaction of high-energy collisions between spin-polarized protons. In preliminary results from data collected in 2011 at $\sqrt{s}=500$ GeV and in 2012 at $\sqrt{s}=200$ GeV, STAR has observed the first non-zero spin asymmetries due to the effects of transversity in proton-proton collisions. Studying these effects through both jet+hadron and di-hadron production channels and across a range of collision energy yields the potential not only to extend understanding of transversity beyond the current kinematic reach but also to address longstanding theoretical questions concerning the universality and evolution of transversity and polarized fragmentation functions. From the 2011 dataset STAR has also released the first preliminary measurements sensitive to the Sivers TMD PDF in weak-boson production. Weak boson production provides an ideal tool for isolating the unconstrained sea-quark Sivers PDF and may provide sensitivity to the expected modified universality of the Sivers PDF when compared to SIDIS. These exploratory measurements pave the way for future higher precision inv
-
RIKEN Lunch Seminar
"Dysonian dynamics of the Ginibre ensemble"
Presented by Piotr Warchol, Jagiellonian University
Thursday, May 21, 2015, 12:30 pm
Building 510 Room 2-160Hosted by: Tomomi Ishikawa
I will present a study of the time evolution of Ginibre matrices whose elements undergo Brownian motion. The non-Hermitian character of the Ginibre ensemble binds the dynamics of eigenvalues to the evolution of eigenvectors in a non-trivial way, leading to a system of coupled nonlinear equations resembling those for turbulent systems. We will formulate a mathematical framework allowing simultaneous description of the flow of eigenvalues and eigenvectors, and unravel a hidden dynamics as a function of new complex variable, which in the standard description is treated as a regulator only. We shall solve the evolution equations for large matrices and demonstrate that the non-analytic behavior of the Green's functions is associated with a shock wave stemming from a Burgers-like equation describing correlations of eigenvectors. I will start by reviewing similar notions in a simpler, Hermitian setting. Joint work with Zdzislaw Burda, Jacek Grela, Maciej A. Nowak and Wojtek Tarnowski (Phys.Rev.Lett. 113 (2014) 104102).
-
Nuclear Physics Seminar
"Low pT photon production at confinement: The missing piece to the direct photon puzzle"
Presented by Dr. Sarah Campbell, Columbia University
Tuesday, May 19, 2015, 11 am
Small Seminar Room, Bldg. 510Hosted by: Jin Huang
Low pT direct photons in Au+Au collisions are produced in excess of the TAA-scaled p+p yields and with a large azimuthal anisotropy, v2. This talk considers that these low pT direct photons are produced by radially boosted quarks undergoing soft-gluon mediated quark-anti-quark interactions as the system becomes color-neutral. A Monte Carlo simulation of direct photons and Chi-squared comparisons of the published PHENIX direct photon and identified particle v2 data are used to test this description. The Monte Carlo simulation reproduces the shape of the direct photon pT excess and the resulting direct photon v2 agrees, despite being systematically low, with the published 0-20% and 20-40% Au+Au low pT direct photon v2 in both centralities. Comparisons to recent preliminary direct photon results will also be shown.
-
C-AD Accelerator Physics Seminar
"A Robinson Wiggler for Lifetime and Brilliant Improvement at the Metrology Light Source"
Presented by Tobias Goetsch, Helmholtz-Zentrum, Germany
Thursday, May 14, 2015, 4 pm
Large Conf. Rm. Bldg. 911B, Rm. A202Hosted by: Wolfram Fischer
"The beam lifetime in electron storage rings concerns machines running in decay mode as well as machines doing top-up. A standard procedure to increase the lifetime is via bunch lengthening as the lifetime depends on the electron density in the bunch. Bunch lengthening is typically achieved with higher harmonic (Landau) cavities. There are several advantages in using a different approach: it is possible to increase the bunch length by installing a transverse gradient (Robinson) Wiggler, which allows to transfer damping between the horizontal and the longitudinal plane. While increasing the bunch length, the horizontal emittance is being reduced yielding advantages regarding the source size depending on the magnet optics. At the Metrology Light Source, a primary source standard used by Germanys national metrology institute (Physikalisch-Technische Bundesanstalt), such a scheme is being investigated. The prospects are higher brilliance for the important beamlines together with a lifetime improvement in the order of 100 %."
-
Particle Physics Seminar
"Dark matter search results from the PandaX-I experiment"
Presented by Mengjiao Xiao, Shanghai Jiao Tong University
Thursday, May 14, 2015, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Elizabeth Worcester
The dark matter is a leading candidate to explain gravitational effects observed in galactic rotational curves, galaxy clusters, and the large scale structure formation, etc. The nature of dark matter is one of the most fundamental problems in physics. Proposals of dark matter candidates usually involve new physics and new particles. Among the various candidates, one compelling class of particles are WIMPs (Weakly Interacting Massive Particles). WIMPs are being studied in colliders, indirect and direct detection experiments. In recent years, new techniques in WIMP direct detection using noble liquids (xenon, argon) have shown exceptional potential due to the capability of background suppression and discrimination, and scalability to large target masses. PandaX is a low threshold dual-phase xenon dark matter experiment operating at the China Jin-Ping Underground Laboratory (CJPL). The PandaX detector is staged. We released the first dark matter search data for PandaX-I on August 2014. In this talk, I will give an introduction to the PandaX-I detector, and then followed by the details of the physics analysis as well as the latest results.
-
RIKEN Lunch Seminar
"Geometrical scaling - a window to saturation"
Presented by Michal Praszalowicz, Jagiellonian University
Thursday, May 14, 2015, 12:30 pm
Building 510 Room 2-160Hosted by: Daniel Pitonyak
Geometrical is a consequence of a traveling wave solution of the non-linear QCD evolution equation, so called Balitski-Kovchegov equation. We shall demonstrate the existence of GS in various high energy reactions. Among different consequences of GS there is a linear rise of charged particle multiplicity (Nch) and mean transverse momentum (pT) with scattering energy. Furthermore, a correlation of meant pT and Nch is predicted to scale in a way that depends on the the way particles are produced from the volume excited in a hadron-hadron scattering. This is mostly visible in heavy ion collisions at different centralities.
-
Physics Colloquium
"Where Did Half the Starlight in the Universe Go"
Presented by Mark Devlin, University of Pennsylvania
Tuesday, May 12, 2015, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Peter Yamin
We believe that approximately half of all the light from stars is absorbed and reprocessed by dust. The resulting emission is grey body with a temperature near 30 Kelvin. The COBE satellite made the first measurements of the resulting Far Infrared Background (FIRB), but since that time, we have been unable to resolve the background into individual galaxies. The Balloon-borne Large Aperture Submillimeter Telescope (BLAST) was designed to do this job. Its three bands at 250, 350, and 500 microns span the peak in emission for galaxies at z=1. I will discuss the BLAST experiment and present results from our measurements of resolved and unresolved galaxies. I will also discuss the implications for star formation in our own galaxy and how dust is changing the way we look at current and future searches for primordial gravity waves with the Cosmic Microwave Background.
-
Nuclear Theory/RIKEN Seminar
"Solving the NLO BK equation in coordinate space"
Presented by Tuomas Lappi, University of Jyvaskyla
Friday, May 8, 2015, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Soeren Schlichting
We present results from a numerical solution of the next-to-leading order (NLO) Balitsky-Kovchegov (BK) equation in coordinate space in the large Nc limit. We show that the solution is not stable for initial conditions that are close to those used in phenomenological applications of the leading order equation. We identify the problematic terms in the NLO kernel as being related to large logarithms of a small parent dipole size, and also show that rewriting the equation in terms of the "conformal dipole" does not remove the problem. Our results qualitatively agree with expectations based on the behavior of the linear BFKL equation.
-
Nuclear Theory/RIKEN Seminar
"Applications of Soft-Collinear Effective theory to hadronic and nuclear collisions"
Presented by Ivan Vitev, Los Alamos National Laboratory
Friday, May 1, 2015, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Soeren Schlichting
Effective field theory (EFT) is a powerful framework based on exploiting symmetries and controlled expansions for problems with a natural separation of energy or distance scales. EFTs are particularly important in QCD and nuclear physics. An effective theory of QCD, ideally suited to jet applications, is Soft-Collinear Effective Theory (SCET). Recently, first steps were taken to extend SCET and describe jet evolution in strongly-interacting matter. In this talk I will demonstrate that the newly constructed theory, called SCETG, allows us to go beyond the traditional energy loss approximation in heavy ion collisions and unify the treatment of vacuum and medium-induced parton showers. It provides quantitative control over the uncertainties associated with the implementation of the in-medim modification of hadron production cross sections and allows us to accurately constrain the coupling between the jet and the medium. I will further show how SCET and SCETG can be implemented to evaluate reconstructed jet observables, such as jet shapes.
-
Nuclear Theory/RIKEN seminar
"Heavy Hadrons under Extreme Conditions"
Presented by Laura Tolos, Instituto de Ciencias del Espacio (IEEC-CSIC)
Friday, April 24, 2015, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Soeren Schlichting
Hadrons under extreme conditions of density and temperature have captured the interest of particle and nuclear physicists as well as astrophysicists over the years in connection with an extensive variety of physical phenomena in the laboratory as well as in the interior of stellar objects, such as neutron stars. One of the physics goals is to understand the origin of hadron masses in the context of the spontaneous breaking of the chiral symmetry of Quantum Chromodynamics (QCD) at low energies in the non-perturbative regime and to analyze the change of the hadron masses due to partial restoration of this symmetry under extreme conditions. Lately other proper QCD symmetries have also become a matter of high interest, such as heavy-quark flavor and spin symmetries. These symmetries appear when the quark masses become larger than the typical confinement scale and they are crucial for characterizing hadrons with heavy degrees of freedom. In this talk I will address the properties of heavy hadrons under extreme conditions based on effective theories that incorporate the most appropriate scales and symmetries of QCD in each case. With the on-going and upcoming research facilities, the aim is to move from the light-quark to the heavy-quark sector and to face new challenges where heavy hadrons and new QCD symmetries will play a dominant role.
-
Biological, Environmental, & Climate Sciences (BECS) Department Seminar
"High-resolution CAM5 simulations of varying complexity"
Presented by Kevin Reed, Stony Brook University
Friday, April 24, 2015, 10 am
Conference Room, Bldg 815EHosted by: Ernie Lewis
In our continued effort to understand the climate system and improve its representation in general circulation models (GCMs) it is crucial to develop new methods to evaluate these models. This is certainly true as the GCM community advances towards high horizontal resolutions (i.e., grid spacing less than 50 km), which will require interpreting and improving the performance of many model components. Idealized, or reduced complexity, frameworks can be used to investigate how model assumptions impact behavior across scales. This work makes use of a range of National Center for Atmospheric Research and Department of Energy Community Atmosphere Model version 5 (CAM5) simulations, ranging from simplified global radiative-convective equilibrium (RCE) simulations to full decadal simulations of present-day and future climate. The various CAM5 configurations provide useful insights into the model's ability to simulate extreme precipitation events and tropical cyclones. Furthermore, the impact of horizontal resolution and the choice of CAM5 dynamical core on the simulation of extreme events will be explored. Finally, time slice experiments using the Representative Concentration Pathway (RCP) 8.5 scenario for greenhouse gas concentrations are assessed and compared to present-day simulations. Overall, this work is part of a continued effort to understand how weather extremes may vary in a changing climate using next-generation high-resolution climate models.
-
Particle Physics Seminar
"(Real) Early Universe Cosmology with Quark Gluon Plasma"
Presented by Niayesh Afshordi, Perimeter Institute for Theoretical Physics
Thursday, April 23, 2015, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Morgan May
An intriguing possibility that can address pathologies in both early universe cosmology (i.e. the horizon problem) and quantum gravity (i.e. non-renormalizability), is that particles at very high energies and/or temperatures could propagate arbitrarily fast. In this talk, I introduce Thermal Tachyacoustic Cosmology (TTC), i.e. this scenario with thermal initial conditions. We find that a phase transition in the early universe, around the scale of Grand Unified Theories (GUT scale; T∼10^{15} GeV), during which the speed of sound drops by several orders of magnitude within a Hubble time, can fit current CMB observations. However, I will then argue that cosmological bounds on the density of primordial black holes suggest that Lorentz invariance in the primordial thermal plasma may not recover until much lower temperatures, close to the QCD phase transition. This presents the exciting possibility of testing this scenario in the thermal plasma produced in relativistic heavy ion collisions.
-
Particle Physics Seminar
"Implications of Cosmological Observations for History of Early Universe"
Presented by Ghazal Geshnizjani, University of Waterloo/ Perimeter Institute for Theoretical Physics
Wednesday, April 22, 2015, 3 pm
Building 510 Room 2-160Hosted by: Morgan May
I will argue that any theory of early universe that matches cosmological observations should include a phase of accelerated expansion (i.e. inflation) or it has to break at least one of the following tenets of classical general relativity: Null Energy Conditions (NEC), sub-luminal signal propagation, or sub-Planckian energy densities. This proof extends to a large class of theories with higher (spatial) derivative or non-local terms in the action as well. Interestingly, only theories in the neighbourhood of Lifshitz points with ω ∠k^0 and k^3 are excluded from the proof. I will also discuss in what sense detecting primordial gravitational waves is a smoking gun for inflation.
-
Condensed-Matter Physics & Materials Science Seminar
"Establishing an Atomistic Picture of Gas Adsorption in Metal Organic Frameworks"
Presented by Anna Plonka, SUNY-Stony Brook, Poland
Wednesday, April 22, 2015, 1:30 pm
ISB Bldg. 734, Conf. Rm. 201 (upstairs)Hosted by: Simon Billinge/Emil Bozin
Selective adsorption and sequestration of carbon dioxide from sources of anthropogenic emissions is important to mitigate the growing level of the atmospheric CO2. Solid state adsorbents, such as metal organic frameworks (MOFs), are proposed as an alternative to the currently used toxic and corrosive alkanolamine solutions. Experimental gas sorption studies of MOFs usually focus on gas isotherms measurements that, while providing the necessary information on the overall gas uptake and framework behavior upon gas loading, yield limited information on the mechanism of the gas adsorption. Molecular level understanding of gas adsorption in MOFs is an important problem and the most detailed structural models necessary to elucidate the adsorbate-adsorbent interaction can be obtained with the crystallographic techniques. This talk will present the recent exciting discoveries of CO2 and hydrocarbon adsorption in MOFs. In contrast to current trends in the design of MOFs, we discovered the unique mechanism responsible for a high CO2/N2 adsorption selectivity in a Ca-based MOF: Ca(sdb), (sdb: 4,4'-sulfonyldibenzoate), even in the presence of water in the gas stream. Single crystal XRD (SCXRD) experiments of gas loaded samples revealed that the v-shaped linker provides a "pi-pocket" formed by two phenyl rings, and that CO2 locate between the rings, resulting in a high heat of adsorption. To determine the gas adsorption performance in situ in the presence of water, we used differential scanning calorimetry technique (XRD-DSC) that allows for measuring enthalpy while collecting X-ray diffraction patterns, to evaluate the structural response during the gas adsorption. The XRD-DSC technique and single crystal diffraction were further used to evaluate the CO2 adsorption in a Cd-analog of Ca(sdb), hydrocarbon adsorption in two Ca-based MOFs and gate opening mechanism in a Mn-based MOF. The knowledge acquired can promote the directed synthetic search for novel
-
Physics Colloquium
"Neutrinos and friends in the past and present universe"
Presented by Alex Kusenko, UCLA
Tuesday, April 21, 2015, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Morgan May
Neutrinos play a role in various aspects of cosmology, including production of light elements, and the rate of expansion of the universe. Furthermore, the neutrino masses imply the likely existence of right-handed neutrinos, which can exist in the form of dark matter, and which can explain the matterantimatter asymmetry of the universe. I will discuss the many faces ordinary and hypothetical neutrinos in cosmology.
-
Center for Data-Driven Discovery C3D
"Computing Intensive Problems in Cosmology"
Presented by Anze Slosar
Tuesday, April 21, 2015, 2 pm
John Dunn Seminar Room, Bldg. 463Hosted by: Robert Harrison
Cosmology is a branch of physics that studies the whole universe as a single physical system. Computing intensive methods are used throughout, both for data analysis and for theoretical modeling. The computational difficulties are in most cases due to existence of gravitational force which is important at all scales. This makes problems fundamentally different from problems in particle physics where each collision event can be considered to be statistically independent. In simulations, it is necessary to take into account the force contribution of any particle to any other and in data analysis the correlations between any two measurements. I will overview problems, solutions and current limitations. Time permitting, I will describe more technical aspects of the code we are developing to analyze data from the spectroscopic datasets.
-
Condensed-Matter Physics & Materials Science Seminar
"Competing Superexchange Interactions in Double Perovskite Osmates"
Presented by Ryan Morrow, Ohio State University
Monday, April 20, 2015, 1:30 pm
ISB Bldg. 734, Conf. Rm. 201 (upstairs)Hosted by: Simon Billinge/Emil Bozin
Double perovskites, A2BB'O6, containing mixed transition metal ions have exhibited numerous desirable properties such as colossal magnetoresistance, half metallic transport, and high temperature ferrimagnetism. However, a predictive understanding of the superexchange mechanisms which control the magnetism of these materials when they are insulating and B is 3d transition metal and B' is a 4d or 5d transition metal has remained elusive. In this work, a number of insulating double perovskite osmates, A2BOsO6 (A=Sr,Ca,La; B=Cr,Fe,Co,Ni) have been chosen and studied using magnetometry, specific heat, XMCD, and neutron powder diffraction techniques in order to systematically probe the effects of electronic configuration and bonding geometry on the magnetic ground state. It is concluded that the magnetic properties of these materials are controlled by a competition between short range B��'O��'Os and long range superexchange interactions which are sensitive to bonding geometry resulting in tunability of the magnetic ground state.
-
Nuclear Physics & RIKEN Theory Seminar
"Consistency of Perfect Fluidity and Jet Quenching in semi-Quark-Gluon Monopole Plasmas"
Presented by Jiechen Xu, Columbia University
Friday, April 17, 2015, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Soeren Schlichting
Abstract: We utilize a new framework, CUJET3.0, to deduce the energy and temperature dependence of jet transport parameter, q^(E>10GeV,T), from a combined analysis of available data on nuclear modification factor and azimuthal asymmetries from RHIC/BNL and LHC/CERN on high energy nuclear collisions. Extending a previous perturbative-QCD based jet energy loss model (known as CUJET2.0) with (2+1)D viscous hydrodynamic bulk evolution, this new framework includes three novel features of nonperturbative physics origin: (1) the Polyakov loop suppression of color-electric scattering (aka "semi-QGP" of Pisarski et al) and (2) the enhancement of jet scattering due to emergent magnetic monopoles near Tc (aka "magnetic scenario" of Liao and Shuryak) and (3) thermodynamic properties constrained by lattice QCD data. CUJET3.0 reduces to v2.0 at high temperatures T>400 MeV, but greatly enhances q^ near the QCD deconfinement transition temperature range. This enhancement accounts well for the observed elliptic harmonics of jets with pT>10 GeV. Extrapolating our data-constrained q^ down to thermal energy scales, E∼2 GeV, we find for the first time a remarkable consistency between high energy jet quenching and bulk perfect fluidity with η/s∼T3/q^∼0.1 near Tc.
-
Particle Physics Seminar
"Cosmology with Strong Gravitational Lenses"
Presented by Phil Marshall, SLAC National Accelerator Laboratory
Thursday, April 16, 2015, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Anze Slosar
Strong gravitational lenses have become an important astronomical tool: they allow us to make accurate measurements of galaxy masses, they provide a magnified view of the distant universe, and they allow us to constrain cosmological parameters. In particular, the time delays in multiply-imaged quasar systems enable measurements of distance in the Universe each with around 5% precision. I will present our recent measurement of time delay distance in two galaxy-scale lens systems. For us to realize the potential of this cosmological probe, we need to increase the size of our lens sample, and continue to improve the accuracy of its analysis. I will discuss the potential of LSST to provide a sample of several hundred lensed quasars with well-measured time delays that would enable competitive and complementary constraints on Dark Energy, and describe our ongoing investigations of how to find lenses, infer their time delays and model their mass distributions accurately, and account for weak lensing effects from external mass structures.
-
Nuclear Theory/RIKEN seminar
"Hydrodynamics Beyond the Gradient Expansion: Resurgence and Resummation"
Presented by Michael Heller, Perimeter Institute
Friday, April 10, 2015, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Soeren Schlichting
Consistent formulations of relativistic viscous hydrodynamics involve short lived modes, leading to asymptotic rather than convergent gradient expansions. In this talk I will consider the Mueller-Israel-Stewart theory applied to a longitudinally expanding quark-gluon plasma system and identify hydrodynamics as a universal attractor without invoking the gradient expansion. I will give strong evidence for the existence of this attractor and then show that it can be recovered from the divergent gradient expansion by Borel summation. This requires careful accounting for the short-lived modes which leads to an intricate mathematical structure known from the theory of resurgence.
-
Physics Colloquium
"The Proton and the Future of Particle Physics"
Presented by Richard Hill, Univ. Chicago
Tuesday, April 7, 2015, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Peter Petreczky
The venerable proton continues to play a central role in fundamental particle physics. Neutrinos scatter from protons in neutrino oscillation experiments, Weakly Interacting Massive Particles (WIMPs) are expected to scatter from protons in dark matter searches, and electrons or muons are bound by protons in precision atomic spectroscopy. Our understanding of the proton is an obstacle to the success of next generation experiments hoping to discover CP violation in the lepton sector and determine the neutrino mass hierarchy, discover the particle nature of dark matter, or reveal new interactions such as those that violate lepton universality. In this talk I present (i) an overview of the current state of knowledge in the neutrino sector, and theoretical advances that will determine a crucial missing ingredient in the predicted signal process of neutrino-nucleus scattering at a Long Baseline Neutrino Facility (ii) the first complete calculation of the scattering cross section of a proton on a static electroweak source, which determines WIMP-nucleus scattering rates at underground direct detection experiments and (iii) the status of the proton radius puzzle, whose most "mundane" resolution requires a 5 standard deviation shift in the value of the Rydberg constant. I describe how each of these problems has spurred the development of powerful new methods in effective quantum field theory.
-
Condensed-Matter Physics & Materials Science Seminar
"2-dimensional Superconductivity at the LaAlO3/SrTiO3 Interface"
Presented by Jean-Marc Triscone, DQMP, University of Geneva, Switzerland
Tuesday, April 7, 2015, 1:30 pm
ISB Bldg. 734, Conf. Rm. 201 (upstairs)Hosted by: Ivan Bozovic
The interface between LaAlO3 and SrTiO3, two good band insulators, which was found in 2004 to be conducting [1], and, in some doping range, superconducting with a maximum critical temperature of about 200 mK [2] is attracting of lot of attention. The electronic structure of the system displays signatures of confinement and of the d-character of the carriers. This electron liquid has a thickness of a few nanometers at low temperatures and a low electronic density. Being naturally sandwiched between two insulators, it is ideal for performing electric field effect experiments that allow the carrier density to be tuned and the phase diagram of the system to be determined [3]. I will discuss in this presentation superconductivity, the phase diagram of the system and the link with bulk doped SrTiO3, spin orbit [4], and an approach that allows superconducting coupling between different gases to be studied. I will also discuss recent thermopower measurements that allow access to localized electronic states [5]. [1] A. Ohtomo, H. Y. Hwang, Nature 427, 423 (2004). [2] N. Reyren, S. Thiel, A. D. Caviglia, L. Fitting Kourkoutis, G. Hammerl, C. Richter, C. W. Schneider, T. Kopp, A.-S. Ruetschi, D. Jaccard, M. Gabay, D. A. Muller, J.-M. Triscone and J. Mannhart, Science 317, 1196 (2007). [3] A. Caviglia, S. Gariglio, N. Reyren, D. Jaccard, T. Schneider, M. Gabay, S. Thiel, G. Hammerl, J. Mannhart, and J.-M. Triscone, Nature 456, 624 (2008). [4] A.D. Caviglia, M. Gabay, S. Gariglio, N. Reyren, C. Cancellieri, and J.-M. Triscone, Physical Review 104, 126803 (2010). [5] I. Pallecchi, F. Telesio, D. Li, A. Fête, S. Gariglio, J.-M. Triscone, A. Filippetti, P. Delugas, V. Fiorentini, and D. Marré, to appear in Nature Communications.
-
Nuclear Physics Seminar
"New Studies of Elastic Nucleon Form Factors"
Presented by Dr. Seamus Riordan, Stony Brook University
Tuesday, April 7, 2015, 11 am
Small Seminar Room, Bldg. 510Hosted by: Jin Huang
The electromagnetic form factors of the nucleon provide experimental access to the underlying charge and magnetic moment distributions arranged by the strong nuclear force. These form factors provide excellent testing grounds for QCD and QCD-inspired models and are fundamentally important in understanding non-perturbative strong force physics. By studying them over a broad range of momentum transfers, they provide insight into the underlying mechanisms relevant to the generation of nucleon structure. At low Q2 there is presently a controversy regarding the charge radius measurements of the proton. At high Q2, scaling of the form factors are presently being studied in the context of a transition from soft QCD interactions. In this talk I will provide an overview of our present experimental of elastic nucleon form factors, review their context within current theoretical models, discuss upcoming future measurements at Jefferson Lab, in particular the Super Bigbite program.
-
C-AD Accelerator Physics Seminar
""Solid-State Laser Engineering for Inertial Confinement Fusion Laser Systems Applications""
Presented by Dr. Andrey Okishev
Friday, April 3, 2015, 4 pm
Bldg 911B., Large Conf.Rm., Rm. A202"Solid-state laser concepts for ICF laser system applications including master oscillator, regenerative amplifier, OPO, and fiber-based front-end are discussed. Applications for the ICF laser system front-end, laser temporal diagnostics testing, laser damage testing, ASE suppression for OPCPA pump, energetic picosecond pulse generation without mode locking, cryogenic target layering, complex multi-FM pulses generation are described."
-
Nuclear Theory/RIKEN seminar
"Gravitational collapse, holography and hydrodynamics in extreme conditions"
Presented by Paul Chesler, Harvard University
Friday, April 3, 2015, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Soeren Schlichting
A remarkable observation from RHIC and the LHC is that the quark-gluon plasma produced in heavy-ion collisions behaves as a strongly coupled and nearly ideal liquid. Data also suggests that the debris produced by proton-nucleus collisions can also behave as a liquid. Understanding the dynamics responsible for the rapid equilibration of such tiny droplets is an outstanding problem. In recent years holography has emerged as a powerful tool to study non-equilibrium phenomena, mapping challenging quantum dynamics onto the classical dynamics of gravitational fields in one higher dimension. In the dual gravitational description the process of quark-gluon plasma formation and equilibration maps onto the process of gravitational collapse and black hole formation. I will describe how one can apply techniques and lessons learned from numerical relativity to holography and present recent work on holographic models of high energy collisions and the applicability of hydrodynamics to tiny droplets of quark-gluon plasma.
-
Particle Physics Seminar
"Measurement of the pion polarizability at COMPASS"
Presented by Jan Friedrich, Technische Universität München, Germany
Friday, April 3, 2015, 10 am
Small Seminar Room, Bldg. 510Hosted by: Ketevi A. Assamagan
For more than a decade, the COMPASS experiment at the CERN Super Proton Synchrotron has been tackling the measurement of the electromagnetic polarizability of the charged pion, which describes the stiffness of the pion against deformation in electromagnetic fields. Previous experiments date back to the 1980's in Serpukhov (Russia), where the Primakoff method to study charged-pion interactions with quasi-real photons was first employed. Later also other techniques in photon-nucleon and photon-photon collisions were carried out at different machines. The COMPASS measurement demonstrates that the charged-pion polarizability is significantly smaller than the previous dedicated measurements, roughly by a factor two, with the smallest uncertainties realized so far. The pion polarisability is of fundamental interest in the low-energy sector of quantum chromodynamics. It is directly linked to the quark-gluon substructure and its dynamics in the lightest bound system of strong interaction.
-
Particle Physics Seminar
"Neutrino Oscillations with IceCube"
Presented by Tyce DeYoung, Michigan State University
Thursday, April 2, 2015, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Elizabeth Worcester
The IceCube Neutrino Observatory is the world's largest neutrino detector. Although designed to detect TeV " PeV scale neutrinos from astrophysical accelerators, IceCube's DeepCore infill array permits searches for dark matter and measurements of neutrino oscillations in the 10-100 GeV range. The most recent measurements of muon neutrino disappearance with IceCube DeepCore will be presented, and prospects for future neutrino physics measurements with IceCube and the proposed PINGU array will be discussed
-
RIKEN Lunch Seminar
"Spin-Orbit Coupling in an Unpolarized Heavy Nucleus"
Presented by Matt Sievert, BNL
Thursday, April 2, 2015, 12:30 pm
Building 510 Room 2-160Hosted by: Daniel Pitonyak
The next-generation Electron-Ion Collider (EIC) will make high precision measurements of spin-dependent observables at high energies on nuclear targets. This unique nuclear physics laboratory will bring together access to the multitude of spin-spin and spin-orbit structures which can exist in hadronic targets, and the high color-charge densities which generate the most intense gluon fields permitted by quantum mechanics. The interplay between those two features gives rise to new physical mechanisms which translate these spin-orbit structures into the observed cross-sections, and it makes these mechanisms amenable to first-principles calculation. In this talk, I will discuss the spin-orbit structure of quarks within an unpolarized heavy nucleus in the quasi-classical approximation. The possibility of polarized nucleons with orbital motion inside the unpolarized nucleus generates nontrivial mixing between the spin-orbit structures of the nucleons, and the corresponding structures in the nucleus. This generic feature of a dense quasi-classical system leads to direct predictions testable at an EIC, and in principle allows direct access to the orbital angular momentum in the nucleus.
-
Physics Colloquium
"Hot Jupiters: astrophysical laboratories for extreme weather"
Presented by Rosalba Perna, Stony Brook University
Tuesday, March 31, 2015, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Peter Petreczky
Hot Jupiters, a class of exoplanets orbiting in the proximity of their parent stars, are subjected to a strong irradiating flux that governs their radiative and dynamical properties. It is a regime which is not observed in the giant planets of our solar system. In this talk, I will describe current efforts to understand their radiative and dynamical properties, characterize their atmospheres by means of a variety of techniques, study the interaction of their fast, weakly ionized winds with the planetary magnetic field, and shed light on an evolutionary puzzle known as the problem of inflated radii.
-
Nuclear Physics Seminar
"Molten salt: towards the next generation of nuclear energy"
Presented by Dr. Ondrej Chvala, University of Tennessee
Tuesday, March 31, 2015, 11 am
Small Seminar Room, Bldg. 510Hosted by: Jin Huang
Current nuclear powerplants use almost exclusively highly pressurized water as reactor coolant and heat transfer medium. This limits their operation to relatively low temperatures. Molten alkali-halide salts allow low pressure operation at high temperatures, improving thermal efficiency and operational safety. The talk will cover the history of molten salt reactor development, reasons for the renewed interest, and focus on recent developments of molten salt nuclear technologies in the U.S. and abroad.
-
C-AD Accelerator Physics Seminar
"High-Power Fiber Lasers for Cornell Energy Recovery LINAC"
Presented by Dr. Zhi Zhao, Cornell University
Monday, March 30, 2015, 4 pm
Bldg 911B, Large Conf. Rm. Rm.A202Hosted by: John Skaritka
"In this talk, I will present a description of high-power fiber lasers and beam shaping systems that have been used to achieve low emittance and record high beam current in the Cornell energy recovery LINAC injector. Design, limitation, as well as power scaling of fiber lasers for the future accelerators will be discussed. "
-
Condensed-Matter Physics & Materials Science Seminar
"Printed nanocomposite capacitors for power conversion applications, and solution processed methods for producing ferroic complex oxide nanoparticles"
Presented by Stephen O'Brien, Department of Chemistry, The City college of New York, New York, NY 10031, Energy Institute, City University of New York, NY 10031
Monday, March 30, 2015, 11 am
Conference Room, Building 480Hosted by: Yimei Zhu
I will give an overview of the metacapacitors project, an ARPA-E sponsored project that aims to improve efficiency, functionality and form factor of off-line power converters suitable for LED solid-state lighting, with a view to developing an attractive technology platform for load management and power conversion across a broad range of applications. Based on integrated switched-capacitor (SC) topologies, the project adopts an integrated approach from materials to devices to circuits. We designed capacitors based on high-dielectric nanocrystals, that can be prepared using high throughput microfabrication/nanotechnology techniques, ink deposition and multilayering. The capacitor dielectric, a nanocomposite composed of (Ba,Sr)TiO3 nanocrystals in polyfurfuryl alcohol (BST/PFA, _ > 20 , 100Hz - 1 MHz , loss < 0:01 , 20 kHz ), targets a high volumetric capacitance density and ripple current capability. The capacitors were board-integrated with a custom hybrid-switched-capacitor resonant (HSCR) DC-DC converter, tested and demonstrated to operate with high efficiency. The methodology for preparing the capacitor dielectric films relies on a novel method to prepare complex oxides, followed by evaporatively driven self-assembly into thin films. I'll review rational synthetic design, multigram scaling, and dispersion formulation design, as well as recent advances in the synthesis and characterization of novel multiferroic and ferroelectric complex oxides. STEPHEN O'BRIEN is an Associate Professor of Chemistry at City College New York and a member of the CUNY Energy Institute. He holds appointments on the Doctoral Faculty of the CUNY Graduate Center and Grove School of Engineering. Steve is a researcher in nanomaterials synthesis, properties and structural characterization: nanoparticle synthesis and self-assembly into superlattices, transition metal oxide nanomaterials, high k dielectrics/memory materials. He is published in over
-
C-AD Accelerator Physics Seminar
""Spin Dynamics Modeling in the AGS Based on a Stepwise Ray-Tracing Method""
Presented by Yann Dutheil, BNL
Friday, March 27, 2015, 4 pm
Bldg 911B, Large Conf. Rm. Rm. A202"The AGS provides a polarized proton beam to RHIC. The beam is accelerated in the AGS from Gγ = 4.5 to Gγ = 45.5 and the polarization transmission is critical to the RHIC spin program. In the recent years, various systems were implemented to improve the AGS polarization transmission. These upgrades include the double partial snakes configuration and the tune jumps system. However, 100 % polarization transmission through the AGS acceleration cycle is not yet reached. Understanding the sources of depolarization in the AGS is critical to improve the AGS polarized proton performances. The complexity of beam and spin dynamics, which is in part due to the specialized Siberian snake magnets, drove a strong interest for original methods of simulations. For that, the Zgoubi code, capable of direct particle and spin tracking through field maps, was used to model the AGS. The Zgoubi model of the AGS will be introduced and recent results obtained through multiturn tracking will be shown. Selected example will highlight the relevance of the Zgoubi simulations to improve the polarization transmission in the AGS."
-
Particle Physics Seminar
"Nue appearance analysis in NOvA"
Presented by Jianming Bian, University of Minnesota
Thursday, March 26, 2015, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Elizabeth Worcester
The NOvA experiment is a long base-line accelerator based neutrino oscillation experiment. It uses the upgraded NuMI beam from Fermilab and measures electron neutrino appearance and muon neutrino disappearance at its far detector in Ash River, Minnesota. Goals of the experiment include measurements of theta13, mass hierarchy and the CP violating phase. NOvA has begun to take neutrino data and first neutrino candidates are observed in its far detector. This talk provides an introduction to the scientific reach of the experiment, the detector construction and the nue appearance analysis, as well as the first data in near and far detectors.
-
C-AD Accelerator Physics Seminar
""Beam-Beam Effects and Landau Damping in the LHC and HL-LHC""
Presented by Claudia Tambasco, CERN, Italy
Thursday, March 26, 2015, 2 pm
Bldg 911B, Large Conf. Rm. Rm. A202Hosted by: Wolfram Fischer
"The Large Hadron Collider (LHC) at CERN is a high-energy circular hadron collider designed to provide a maximum center of mass energy of 14 TeV and a peak luminosity of L = 1e34-1e35 cmâˆ'2 sâˆ'1 . The LHC 2012 RUN has shown strong coherent transverse instabilities developing at top energy (4TeV) which where causing large particle losses and in many cases also beam dumps. Coherent modes driven by the machine impedance are normally Landau damped by the use of octupole magnets which are regularly powered to ensure enough detuning with amplitude. Also beam-beam effects contribute to the detuning with amplitude and they could therefore increase or decrease the Landau damping range of frequencies depending on the spread obtained from the octupoles. The interplay between impedance, Landau octupoles and beam-beam interactions defines the stability limits of the accelerator that can be evaluated by the so called stability diagrams. In the tune spread analysis there is no information on possible mechanisms which modify the particle distribution, second fundamental ingredient of the Landau damping. Therefore it is fundamental to explore experimentally, through Beam Transfer Function measurements, and with simulations the effects of different distributions to the stability diagrams. The High Luminosity Large Hadron Collider (HL-LHC) projects aims to extend the LHC discovery potential and it is designed to operate with beams of much higher brightness resulting in much stronger beam-beam interactions. Landau damping properties for this scenario are also presented."
-
HET/RIKEN seminar
"Flavored Dark Matter with Weak Scale Mediators"
Presented by Can Kilic, The University of Texas, Austin
Wednesday, March 25, 2015, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Chien-Yi Chen
All matter in the Standard Model appears in three generations, with an intricate flavor structure the origin of which is not well understood. This motivates the question whether distinct phenomenological features arise if dark matter (DM) also has a non-trivial flavor structure. In this talk I will review the experimental signatures of this scenario. In the case of lepton-flavored DM, I will argue that the generation of a lepton asymmetry at a high energy scale can also produce a DM asymmetry, which can strongly affect the sensitivity of direct detection experiments, and I will present novel signatures that can appear at colliders and in indirect detection experiments. I will also review the case of top quark-flavored DM with a distinct collider phenomenology including final states of top pairs and missing energy as well the possibility of displaced decays.
-
Physics Colloquium
"Discoveries that changed the world: 1932 - 1942 - James Chadwick & Lise Meitner"
Presented by Gerard Lander, EITU - Karlsruhe
Tuesday, March 24, 2015, 11 am
Large Seminar Room, Bldg. 510Hosted by: Doon Gibbs
From the discovery of the neutron (1932) to the first demonstration of controlled fission (1942) was just ten years; a period that took physics from an occupation of a small number of eccentric gentlemen and (even fewer) ladies to something of concern to, and funding decisions of, Governments all over the world. The shadows of those tumultuous years are still with us, for better or worse. This talk will recount those ten years through the lives of James Chadwick (1891-1974) and Lise Meitner (1878-1968), contemporaries who played pivotal roles in the events, even though, partly because of their retiring personalities, they are often over-shadowed by "larger" figures.
-
Joint NT/RIKEN Seminar
"Flow-like behavior in small systems — Multi-parton interactions and color reconnection effects at the LHC"
Presented by Antonio Ortiz Velasquez, National Autonomous University of Mexico
Friday, March 20, 2015, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Soeren Schlichting
Collectivity in high multiplicity pp and p-Pb collisions is the most unexpected discovery at the LHC, its origin is still an open question. In heavy ion collisions, collectivity is attributed to final state effects due to the presence of a hot and dense QCD medium, and it is well described by viscous hydrodynamical calculations with fluctuating initial state geometries. Surprisingly, calculations which employ hydrodynamics reproduce qualitatively well the features of p-Pb data, but, the applicability of hydro in small systems faces conceptual problems. This is not the case of other approaches which do not require a medium to be formed and also are able to reproduce qualitatively well some features of data. In this talk it will be shown that multi-parton interactions and color reconnection (CR) produce flow-like effects in high multiplicity pp collisions. A study of the transverse momentum (pT) distribution of identified hadrons as a function of the event multiplicity will be presented. This comprises studies of the average pT vs hadron mass and number of constituent quarks, and a pT differential study using the Boltzmann-Gibbs Blast-Wave model. A comparison between hydro and color reconnection calculations will be presented. In this context, the results from the same study using LHC data (pp, p-Pb and Pb-Pb collisions) will be discussed.
-
Condensed-Matter Physics & Materials Science Seminar
"Graphene on Ir(111), adsorption and intercalation of Cs and Eu atoms"
Presented by Predrag Lazic, Rudjer Boskovic Institute, Croatia
Thursday, March 19, 2015, 1:30 pm
ISB Bldg. 734, Conf. Rm. 201 (upstairs)Hosted by: Tonica Valla
Experimental and theoretical study of Cs and Eu atoms adsorption on graphene on Ir(111) will be presented [1,2]. Graphene on Ir(111) surface is an interesting system because graphene has almost pristine electronic structure in it due to its weak bonding character to iridum surface. The bonding is almost exclusively of the van der Waals type. However adding Cs or Eu atoms graphene gets doped and and nature of binding changes - especially in the case when the atoms intercalate. Density Functional Theory calculations with standard semilocal functionals (GGA) - fail to reproduce experimental findings even qualitatively. Only when the newly developed nonlocal correlation functional is used (vdW-DF) which includes van der Waals interactions, are the calculations in agreement with experiment, revelaing the mechanism of graphene delamination and relamination which is crucial for intercalation and trapping of atoms under the graphene. [1] M. Petrovic et al., Nat. Commun. 4, 2772 (2013). [2] S. Schumacher et al., Nano Lett. 13, 5013 (2013).
-
RIKEN BNL
"The title of my talk is "How Jets and Two-Particle Correlations Impact Our Understanding of the Quark Gluon Plasma"
Presented by Megan Connors, Yale University
Wednesday, March 18, 2015, 2 pm
Building 510 Room 2-160Hosted by: Samuel Aronson
Relativistic heavy ion collisions can reproduce the conditions necessary to form a hot and dense medium known as the Quark Gluon Plasma (QGP), the state of the universe immediately following the Big Bang, in which quarks and gluons are deconfined. Results from experiments at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC), which study the properties of the QGP, will be presented. This seminar will focus on two particle correlations and jet physics results in Pb-Pb and Au-Au collisions at the LHC and RHIC respectively and the prospects for such measurements at the proposed sPHENIX detector. In addition, the implications of using p-p or p-A systems as a reference for these A-A measurements will be discussed. Jets are the result of a hard scattering, which occurs early in the collision process, and probe how partons interact and lose energy in the medium. Two particle correlations are used to study jet physics and energy loss, as well as the underlying event. The interplay between the two is important for understanding how high momentum particles lose energy and for finding where that lost energy goes. To quantify the influence of the QGP on these measurements, it is important to have a good baseline measurement. A-A measurements are typically compared to expectations based on p-p collisions. Recent results from p-A collisions are used to quantify cold nuclear matter effects not captured in p-p collisions. However, p-A measurements have proven to be interesting in their own unexpected way which has implications for physics measurements at the future Electron Ion Collider.
-
Physics Colloquium
"Measuring Dark Matter and Dark Energy with Gravitational Lensing"
Presented by Erin Sheldon, BNL
Tuesday, March 17, 2015, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Morgan May
Gravitational lensing is the bending of light as it passes massive bodies. The amount of deflection is directly related to the mass of the lensing body and the geometrical configuration of the lens-source system. Typical lens configurations involve a distant background galaxy lensed by a much closer foreground galaxy, or cluster of galaxies. The lensing effect can be used to infer the mass of the lens, both luminous and dark matter. Lensing, as a purely geometrical phenomenon has become the most important way to measure the distribution of dark matter in the universe. I will discuss measurements I have made of the dark matter distribution in galaxies and clusters of galaxies using the lensing phenomenon. These measurements, the most precise to date, are consistent with the predictions of the cold dark matter model. Dark energy has accelerated the expansion of the universe at late times, and thus alters the relationship between the observed redshift of galaxies and their true distance from us. Lensing is sensitive to this redshift-distance relationship, and thus dark energy, since the amount of light deflection depends on the relative distances of lens and source. I will discuss the Dark Energy Survey (DES), a survey of the southern sky, now ending our second year of data taking. DES surveys larger volumes of the universe, and probes farther back in time than previous lensing surveys. With DES we will establish lensing as a competitive method to study dark energy. I will discuss preliminary results from DES using galaxy clusters as lenses and distant background galaxies as sources. I will end with a discussion of the new Large Synoptic Survey Telescope (LSST) survey, of which BNL is a member. LSST is a successor of DES, now entering the construction phase. With LSST we will bring lensing to maturity as a probe of dark energy.
-
Nuclear Physics Seminar
"Recent development of quarkonium production in p+p and p+A collisions"
Presented by Yan-Qing Ma, University of Maryland
Tuesday, March 17, 2015, 11 am
Small Seminar Room, Bldg. 510Hosted by: Oleg Eyser
Although the next-to-leading order NRQCD calculation can solve many puzzles of heavy quarkonium production phenomena, it can neither describe data at very high nor very low transverse momentum (pT) region. At very high pT region, a double parton fragmentation formalism was proposed recently, which can systematically reorganize the expansion and resum large logarithms; while at very low pT region, a NRQCD+CGC framework was proposed to take into account the intrinsic transverse momentum and gluon saturation effects. I will talk about these theories and their application on p+p and p+A collisions from RHIC to LHC.
-
Particle Physics Seminar
"Search for Direct Top Squarks"
Presented by Walter Hopkins, University of Oregon
Monday, March 16, 2015, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Ketevi Assamagan
The results of a search for direct pair production of the scalar partner to the top quark using an integrated luminosity of 20/fb of proton-proton collision data at 8 TeV, recorded with the ATLAS detector at the LHC, are reported. The top squark is assumed to decay via stop -> top+LSP where LSP denotes the lightest neutralino in supersymmetric models. The search targets a fully hadronic final state in events with four or more jets and large missing transverse momentum. No significant excess over the Standard Model background prediction is observed, and exclusion limits are reported in terms of the top squark and LSP masses. In addition to the current results, prospects and plans for stop searches in the LHC Run 2 will be discussed.
-
Physics Colloquium
"DOUBLE BETA DECAY AND NEUTRINO MASSES"
Presented by Francesco Iachello, Yale University
Tuesday, March 10, 2015, 3:30 pm
Large Seminar Room, Bldg. 510Hosted by: Peter Petreczky
The question of whether or not neutrinos are Majorana particles and, if so, what is their average mass remains one of the most fundamental problems in physics today. The average neutrino mass can be obtained from neutrinoless double beta decay. The inverse half-life for this process is given by the product of a phase space factor (PSF), a nuclear matrix element (NME) and whatever physics there is beyond the standard model. In this talk, the theory of double beta decay, both with and without the emission of neutrinos, will be reviewed, and recent calculations of the PSF and NME will be presented. From these and from experimental limits on the half-life of neutrinoless double beta decay, one can extract limits on the neutrino mass, both for the exchange of light (mνá1keV) and heavy (mνà 1GeV) neutrinos. Current limits will be discussed. Finally, the question of how many neutrino species there are will be briefly addressed, including the possibility of sterile neutrinos with masses in the intermediate range keV-GeV.
-
Sustainable Energy Technologies Seminar
"Surfactant Free Synthesis of Plasmonic Nanoparticles and Their Application in Optical Detection of Explosives and Ions"
Presented by Devika Sil, Temple University, Philadelphia
Tuesday, March 10, 2015, 2 pm
ISB 734 2nd Floor Seminar Room 201Hosted by: Matthew Eisaman
The localized surface plasmon resonance (LSPR), arising due to the collective oscillation of free electrons in metal nanoparticles, is a sensitive probe of the nanostructure and its surrounding dielectric medium. Synthetic strategies for developing surfactant free nanoparticles providing direct access to the metallic surface that harvest the localized surface plasmons will be discussed first followed by the applications. It is well known that the hot carriers generated as a result of plasmonic excitation can participate and catalyze chemical reactions. One such reaction is the dissociation of hydrogen. By the virtue of plasmonic excitation, an inert metal like Au can become reactive enough to support the dissociation of hydrogen at room temperature, thereby making it possible to optically detect this explosive gas.1 The mechanism of sensing is still not well understood. However, a potential hypothesis is that the dissociation of hydrogen may lead to the formation of a metastable gold hydride with optical properties distinct from the initial Au nanostructures, causing a reversible increase in transmission and blue shift in LSPR. It will also be shown that by tracking the LSPR of bare Au nanoparticles grown on a substrate, the adsorption of halide ions on Au can be detected exclusively. The shift in LSPR frequency is attributed to changes in electron density rather than the morphology of the nanostructures, which is often the case.
-
C-AD Accelerator Physics Seminar
"Polarization Aperture Response for 250 GeV Ramps"
Presented by Dr. Vahid Ranjbad, BNL
Friday, February 27, 2015, 4 pm
Bldg 911B, Large Conf. Rm., Rm A202"Through direct and lattice independent tracking we show how the polarization aperture can be greatly expanded by modifying the 453-nu intrinsic spin resonance next to the main 393+nu resonance. We also explore the conjecture that the structure of the aperture is related to the area of the parametric resonance regions based on the new formulation for the T-BMT equation (given in my recent PRSTAB paper http://journals.aps.org/prstab/pdf/10.110/PhysRevSTAB.18.014001) and how this might explain some of the apparent structure in the polarization profile measurements."
-
Particle Physics Seminar
"The ATLAS H-ZZ(*)-4l decay channel"
Presented by Kalliopi Iordanidou, Columbia University, Nevis Laboratories
Friday, February 27, 2015, 11 am
Small Seminar Room, Bldg. 510Hosted by: Ketevi A. Assamagan
The H->ZZ(*)ïƒ 4l decay channel is the experimentally cleanest signature for the Higgs boson production at the LHC (CERN). The selection of the candidates, the data driven background estimation methods and the property measurements of the Higgs boson are presented using the ATLAS Run-I data. Prospect expectations are explored for the High Luminosity LHC (HL-LHC) scenario.
-
Particle Physics Seminar
"Coherent Charged Pion Production in ArgoNeuT"
Presented by Tingjun Yang, Fermilab
Thursday, February 26, 2015, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Elizabeth Worcester
I will present the first cross section measurements for charged current coherent pion production by neutrinos and antineutrinos on argon. These measurements are performed using the ArgoNeuT detector exposed to the NuMI beam at Fermilab. The results are in a good agreement with the theoretical predictions from GENIE and NuWro.
-
Special Nuclear Physics/HEP Seminar
"Nuclear parton distributions in theory"
Presented by Adam Freese, Florida International University, Miami, FL
Thursday, February 26, 2015, 10 am
Building 510 Room 2-160Hosted by: Thomas Ulrich
Quantum chromodynamics has been extremely successful in describing a multitude of high-energy experiments with aid from the use of universal parton distribution functions. PDFs for the free proton are fairly well-constrained by experiment, but nuclear PDFs require elaboration. Three ingredients are necessary to obtain a nuclear PDF theoretically: (1) an account of the nuclear momentum distribution that includes the latest results regarding short range correlations; (2) a model of how nucleons immersed in the nuclear medium are modified at a quark-gluon level; and (3) the application of QCD evolution to connect the low momentum resolution scales at which the first two ingredients are obtained to the high momentum transfer scales relevant to the LHC and the EIC. These three ingredients will be described in detail, and an example of their application to proton-nucleus collisions at LHC energies will be provided.
-
Physics Workshop
"Brain Circulation Workshop"
Wednesday, February 25, 2015, 9 am
Large Seminar Room, Bldg. 510Hosted by: Rob Pisarski
This is the third workshop for a visiting program between the Japanese Society for the Promotion of Science and the Nuclear, Lattice Gauge, and High Energy Theory groups at Brookhaven. The grant, termed a Brain circulation program, is between Dr. Tetsuo Hatsuda, Chief Scientist at RIKEN, and his colleagues from RIKEN, Kyoto University, and Tsukuba University, and is designed to allow young scientists to visit BNL. In this workshop young scientists from both Japan and BNL will discuss their work.
-
Nuclear Physics Seminar
"Understanding flow fluctuations with Principal Components"
Presented by Derek Teaney, Stony Brook University
Tuesday, February 24, 2015, 11 am
Small Seminar Room, Bldg. 510Hosted by: Jiangyong Jia
We perform a Principal Component Analysis (PCA) of $v_3(p_T)$ in event-by-event hydrodynamic simulations of Pb+Pb collisions at the LHC. The PCA procedure identifies two dominant contributions to the two particle correlation function, which together capture 99.9\% of the squared variance. We find that the subleading flow (which is the largest source of flow factorization breaking in hydrodynamics) is predominantly a response to the radial excitations of a third-order eccentricity. We present a systematic study of the hydrodynamic response to these radial excitations in 2+1D viscous hydrodynamics. Finally, we construct a good geometrical predictor for the orientation angle and magnitude of the leading and subleading flows using two Fourier modes of the initial geometry.
-
Condensed-Matter Physics & Materials Science Seminar
"Non-equilibrium electronic structure and ultrafast dynamics of solid materials"
Presented by Uwe Bovensiepen, Univ. Duisburg-Essen, Germany
Friday, February 20, 2015, 1:30 pm
ISB, Bldg. 734, Conf. Rm. 201 (upstairs)Hosted by: Jonathan Rameau
Optical excitations in solid materials decay typically on femto- to picosecond time scales due to interactions which lead to a redistribution of the excess energy among the electronic, the lattice, and the spin subsystem, before final dissipation. We perform pump-probe experiments in order to analyze these excitations and the action they generate through their relaxation directly in the time domain. In this talk time- and angle-resolved photoemission (tr-ARPES) results which probe the excited state with energy and momentum sensitivity on complex materials like charge density wave compounds [1] and high temperature superconductors [2,3] will be discussed. In the prototype charge density wave material RTe3 (R=Ho, Tb, Dy) we obtained a momentum dependent analysis of the time dependent gap function (k,t) which sheds lights on the amplitude mode and the interaction responsible for the charge density wave formation. In the iron based superconductor material BaFe2As2 the optical excitation induces oscillations in the chemical potential linked to the coherent A1g phonon which modulates the pnictogen height and electronic correlations. In the cuprates pump-induced changes are observed below and above Tc. We obtained evidence for considerable photo-doping effects based on transient changes in the Fermi momentum kF upon optical excitation. Remarkably, the observed changes follow predictions based on chemical doping, which suggests time- and angle-resolved photoemission as a novel method to differentially probe the Fermi surface of complex materials. [1] L. Rettig, J.-H. Chu, I. R. Fisher, U. Bovensiepen, M. Wolf, Faraday Discuss. 171, 1 (2014). [2] J. Rameau, S. Freutel, L. Rettig, I. Avigo, M. Ligges, Y. Yoshida, H. Eisaki, J. Schneeloch, R. D. Zhong, Z. J. Xu, G. D. Gu, P. D. Johnson, U. Bovensiepen, Phys. Rev. B 89, 115115 (2014). [3] L. X. Yang, G. Rohde, T. Rohwer, A. Stange, K. Hanff, C
-
Condensed-Matter Physics & Materials Science Seminar
"Electronic phase separation and magnetic phase behavior in the Ru-doped spin-orbit Mott insulator Sr3Ir2O7"
Presented by Chetan Dhital, Oak Ridge National Laboratory
Wednesday, February 18, 2015, 11 am
ISB Bldg. 734, Conf. Rm. 201 (upstairs)Hosted by: Mark Dean
Recent theoretical and experimental studies have predicted a very interesting electronic phase diagram in 5d iridate system arising due to interplay of spin orbit interaction and the electronic correlation. Spin-orbit Mott phase is one such electronic phase realized in Ruddelsden-Popper (RP) series [Srn+1IrnO3n+1] oxides. Sr3Ir2O7 (n=2) and Sr2IrO4 (n=1) are two representative candidates of this series. Although their ground state properties are studied to some extent, very little is known regarding how the properties of their antiferromagnetic, insulating, parent states evolve upon carrier substitution. One way of experiencing the strength and relevance of electronic correlation in any condensed matter system is by doping charge carriers. The presence of electronic correlations in the host system determines the fate of the dopant and hence stabilizes a new electronic/magnetic ground state. I will discuss about importance of electronic correlations in one such doped system Sr3 (Ir1-xRux) 2O7 using combined neutron scattering, electric transport and magnetization techniques. Our findings demonstrate that correlation effects felt by carriers introduced within in a 5d Mott phase remain robust enough to drive electron localization, a key ingredient in emergent phenomena such as high temperature superconductivity and enhanced ferroic behavior. References: [1]. Dhital, Chetan, et al. "Spin ordering and electronic texture in the bilayer iridate Sr3Ir2O7." Physical Review B 86.10 (2012): 100401. [2]. Dhital, Chetan, et al. "Neutron scattering study of correlated phase behavior in Sr2IrO4." Physical Review B 87.14 (2013): 144405. [3]. Dhital, Chetan, et al. " Carrier localization and electronic phase separation in a doped spin-orbit-driven Mott phase in Sr3 (Ir1â€"xRux) 2O7 (Nature communications,2014)
-
RIKEN/BNL Lunch Time Talk
"Bose-Einstein Condensation, Isotropization, and Thermalization in Overpopulated Systems"
Presented by Jinfeng Liao, Indiana University / RBRC
Thursday, February 12, 2015, 12:30 pm
Building 510 Room 2-160Hosted by: Tomomi Ishikawa
We discuss recent progress, using the kinetic theory framework, in understanding the non-equilibrium evolution of overpopulated systems that resemble the glasma during the early stage of heavy ion collisions. We analyze a number of important factors that influence the course of thermalization in such systems, and in particular their consequences for the nontrivial dynamics driving Bose-Einstein Condensation as well as the isotropization. We discuss recent progress, using the kinetic theory framework, in understanding the non-equilibrium evolution of overpopulated systems that resemble the glasma during the early stage of heavy ion collisions. We analyze a number of important factors that influence the course of thermalization in such systems, and in particular their consequences for the nontrivial dynamics driving Bose-Einstein Condensation as well as the isotropization.
-
High-Energy Physics & RIKEN Theory Seminar
"Electric Dipole Moments, New Physics, and (lattice) QCD"
Presented by Vincenzo Cirigliano, Los Alamos
Wednesday, February 11, 2015, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Sally Dawson
In this talk I will discuss the role of electric dipole moments (EDMs) as probes of physics beyond the Standard Model (BSM). In the first part of the talk I will present an overview of the physics reach of various searches and I will discuss the complementarity of different EDM probes. In the second part of the talk I will discuss ongoing work towards the computation of the BSM-induced neutron and proton EDM using lattice Quantum ChromoDynamics.
-
Condensed-Matter Physics & Materials Science Seminar
"Spin-orbital separation in the quasi-one-dimensional Mott insulator Sr2CuO3"
Presented by Jeroen van den Brink, Institute for Theoretical Solid State Physics, IFW Dresden and Department of Physics, TU Dresden, Germany
Monday, February 9, 2015, 1:30 pm
ISB 201 seminar roomHosted by: Weiguo Yin
When viewed as an elementary particle, the electron has spin and charge. When binding to the atomic nucleus, it also acquires an angular momentum quantum number corresponding to the quantized atomic orbital it occupies. Even if electrons in solids form bands and delocalize from the nuclei, in Mott insulators they retain their three fundamental quantum numbers: spin, charge and orbital. The hallmark of one-dimensional physics is a breaking up of the elementary electron into its separate degrees of freedom. The separation of the electron into independent quasi-particles that carry either spin (spinons) or charge (holons) was first observed fifteen years ago. Here we report observation of the separation of the orbital degree of freedom (orbiton) using resonant inelastic X- ray scattering on the one-dimensional Mott insulator Sr2CuO3. We resolve an orbiton separating itself from spinons and propagating through the lattice as a distinct quasi-particle with a substantial dispersion in energy over momentum, of about 0.2 electronvolts, over nearly one Brillouin zone [1]. [1] J. Schlappa, K. Wohlfeld, K. J. Zhou, M. Mourigal, M. W. Haverkort, V. N. Strocov, L. Hozoi, C. Monney, S. Nishimoto, S. Singh, A. Revcolevschi, J.-S. Caux, L. Patthey, H. M. Rønnow, Jeroen van den Brink and T. Schmitt, Nature 485, 82 (2012).
-
C-AD Accelerator Physics Seminar
""Proton Spin Tracking with Symplectic Orbit Motion""
Presented by Dr. Yun Luo, BNL
Friday, January 30, 2015, 4 pm
Bldg 911B Large Conf. Rm, Rm A202"Symplectic integration had been adopted for orbit tracking in code SimTrack, which has been extensively used for dynamic aperture calculation with beam-beam interaction for the Relativistic Heavy Ion Collider (RHIC). Recently spin motion for protons and synchrotron radiation for electrons have been added to this code. In this talk, the speaker will first review existing spin tracking codes used at BNL, then introduce symplectic integration of orbit motion and implementation of spin tracking based on Thomas-BMT equation. Several tracking examples for AGS (Alternating Gradient Synchrotron), RHIC, and eRHIC will be presented."
-
Particle Physics Seminar
"Silicon Sensor R&D for the ATLAS HL-LHC Upgrade"
Presented by Daniel Muenstermann, University of Geneva
Thursday, January 29, 2015, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Ketevi Assamagan
In the coming years, the LHC will be upgraded to provide much higher luminosity. This implies increased radiation damage, occupany and pile-up for the ATLAS experiment and requires the replacement of the current Inner Detector with an improved all-silicon tracker.
-
Condensed-Matter Physics & Materials Science Seminar
""Progress of RCE processed REBCO Coated Superconductors in Korea""
Presented by Dr. Sang-Soo Oh, Superconductivity Research Center, Korea Electrotechnology Research Institute, Korea, Republic of (South)
Friday, January 23, 2015, 11 am
Bldg. 480 conference roomHosted by: Qiang Li
-
Brookhaven Lecture
"501st Brookhaven Lecture: Negative Particles for Positive Breakthroughs: Characterizing Electrons in Novel Materials at NSLS-II"
Presented by Ignace Jarrige, Photon Sciences Directorate
Wednesday, January 21, 2015, 4 pm
Berkner Hall AuditoriumHosted by: Thomas Watson
During the 501st Brookhaven Lecture, Ignace Jarrige will discuss different ways electrons behave and affect unique materials' properties. He will then explain how the new Soft Inelastic X-ray Scattering (SIX) beamline—an extra-long beamline he is developing at NSLS-II—will measure how x-rays excite atomic bonds in new materials researchers are inventing around the world. Jarrige and his collaborators will use this new tool to unravel mysteries of electrons' collective behavior with unprecedented accuracy as they witness emerging phenomena such as superconductivity—the ability to conduct electricity with zero resistance—magnetism, and other phenomena that could lead to faster trains, more powerful computer processors, and far more efficient electrical grids.
-
Office of Educational Programs Event
"High School Research Program (HSRP) Poster Session 2014"
Tuesday, December 2, 2014, 4 pm
Berkner Hall AuditoriumHosted by: Scott Bronson
Brookhaven National Laboratory's primary focus as an institution is research and development. Students participate in ongoing programs where a BNL scientist mentors a student on a research project during a six week summer session. Students may also work during the academic year, usually to complete their project.
-
Condensed-Matter Physics & Materials Science Seminar
"Band Structure Engineering in Mg2Si1-xSnx and (Bi1-xSbx)2Te3: from Bulk to Surface Transport"
Presented by Wei Liu, Department of Physics, University of Michigan
Tuesday, August 19, 2014, 10:30 am
Bldg. 480 Conference RoomHosted by: Qiang Li
Composition tuning in compound semiconductors allows for band structure engineering, which opens many avenues in fundamental and applied research. Here, I will show the application of band structure engineering in optimizing the electronic properties of bulk thermoelectric materials as well as probing the surface transport of topological insulator thin films. The main motivation of current thermoelectric research is to optimize the figure of merit ZT, so that the efficiency can be improved in (i) recovering waste industrial heat as well as (ii) providing local cooling of electronic devices. However, it is a challenge to independently tune the thermoelectric parameters that lead to high ZTs. We have found that Mg2Si1-xSnx thermoelectric material not only shows excellent thermoelectric performance but also exhibits decoupled Seebeck coefficient (α) and electrical conductivity (σ). We discover the convergence of two conduction bands in this material, which enhances the density-of-states effective mass and α in a large temperature range, without any detrimental effect on σ. Thus, a significantly improved power factor (PF = α2σ) is achieved, which results in a record high ZT in this material. Another material example with interesting consequences of band structure engineering is (Bi1-xSbx)2Te3. This material has become a mainstream material in the research of 3D topological insulators due to their potential to obtain surface transport protected by time-reversal-symmetry. I will show that using molecular beam epitaxy technique we can (i) tune the Bi/Sb ratio and (ii) control the thickness (as thin as several quintuple layers), which allow the observation of a dramatic distinction in electronic transport between high quality films and their bulk counterparts. An insulating-like regime has been obtained, which has enabled studies of magneto-resistance and thermoelectric properties associated with surface states.
-
Environmental Sciences Department Seminar
"CWRF Physics Representation and Climate Prediction at Regional Scales"
Presented by Prof. Xin-Zhong Liang, University of Maryland
Friday, June 20, 2014, 11 am
Bldg 815E Conference RoomHosted by: Wei Wu
The CWRF is developed as a Climate extension of the Weather Research and Forecasting model (WRF) by incorporating numerous improvements in representation of physical processes and integration of external (top, surface, lateral) forcings that are crucial to climate scales, including interactions between landâ€"atmosphereâ€"ocean, convectionâ€"microphysics and cloudâ€"aerosolâ€"radiation, and system consistency throughout all process modules. As a result, the CWRF has demonstrated great capability and excellent performance in simulating the regional climate over U.S. This presentation will focus on the development of CWRF representation of physical processes at regional scales and its added values over the driving general circulation model outputs for seasonal-interannual climate prediction and possible impacts of the present-day model fidelity on future climate projection.
-
Brookhaven Lecture
"495th Brookhaven Lecture: 'To See or Not to See a Warhead: Imaging Nuclear Weapons With Neutrons'"
Presented by Istvan Dioszegi, Nonproliferation and National Security Department
Wednesday, June 18, 2014, 4 pm
Berkner Hall AuditoriumHosted by: Allen Orville
The stakes are high when it comes to world powers and nuclear weaponsâ€"very highâ€"and scientists from Brookhaven Lab's Nonproliferation & National Security Department are developing advanced neutron-imaging techniques to prepare for future inspections. Find out how with Istvan Dioszegi at the 495th Brookhaven Lecture on Wednesday, June 18.
-
Movie Screening & Discussion
"'Particle Fever' Documentary Screening & Panel Discussion"
Sunday, May 18, 2014, 2 pm
Cinema Arts Centre, 423 Park Ave., Huntington, NY"Particle Fever," a new documentary showcasing the hunt for the Higgs boson at CERN's Large Hadron Collider, will be hitting Long Island on Sunday, May 18, at 2 p.m. at the Cinema Arts Centre in Huntington. A panel discussion following the film will feature researchers from Brookhaven Lab and Stony Brook University who played a role in the Higgs search, along with a live video feed from CERN. After the panel discussion, the Centre will host a wine and cheese event to provide attendees with an opportunity to talk with the scientists about their work in an informal setting. Tickets for the event are not yet available as of March 10, but will be announced when they go on sale.
-
Brain Circulation Workshop
"Frontiers of Hadronic Physics: Brains Recirculate Two"
Thursday, March 13, 2014, 9 am
Large Seminar Room, Bldg. 510Hosted by: Taku Izubuchi
A workshop on hadronic physics will be held in the large seminar room on Thursday. This is a collaboration between Prof. T. Hatsuda's group at RIKEN, under the Brain initiative, and the Nuclear Theory, Lattice Gauge Theory, and High Energy Theory Groups.
-
PubSci
"Big Bang Physics and the Building Blocks of Matter"
Presented by Berndt Mueller, Paul Sorensen, Agnes Mocsy, Brookhaven National Laboratory and Pratt Institute
Tuesday, March 11, 2014, 7 pm
Hoptron Brewtique, 22 West Main St., Patchogue, NYPubSci, a new science cafe series, provides a lively setting for the science-interested public to engage in discussions with scientists from Brookhaven National Laboratory in an informal and casual way. For our first event, we'll be joined by physicists who work at Brookhaven's particle collider to talk about how we explore what happened at the dawn of time from a Lab on Long Island. How did the Universe take shape? What binds matter together? How do we answer those questions? You don't need a degree to join the conversation. But you do need to be over 21. (The venue's rules, not ours.) Admission is free. Let us know you're coming - RSVP at the PubSci website.
-
Brookhaven Lecture
"489th Brookhaven Lecture 'Doing More With Less: Cost-effective, Compact Particle Accelerators'"
Tuesday, October 22, 2013, 4 pm
Berkner Hall AuditoriumHosted by: Allen Orville
During his talk, Dejan Trbojevic of Brookhaven Lab's Collider-Accelerator Department will provide an overview of accelerator technologies and techniquesâ€"particularly a non-scaling, fixed-focused alternating gradientâ€"to focus particle beams using fewer, smaller magnets. He will then discuss how these technologies will benefit eRHIC and other applications, including particle therapies being developed to combat cancer.
-
Environmental Sciences Department Seminar
"Particle-Resolved Model Analysis of Black Carbon Aging"
Presented by Laura Fierce, University of Illinois at Urbana-Champaign
Wednesday, August 14, 2013, 11 am
Conference Room, Bldg 815EThe size and composition of particles containing black carbon (BC) are modified soon after emission by condensation of secondary aerosol and coagulation with other particles, known collectively as "aging" processes. Although this change in particle properties is widely recognized, the timescale for transformation is not well constrained. In this work, we simulated aerosol aging with the particle-resolved model PartMC-MOSAIC and extracted aging timescales based on changes in particle cloud condensation nuclei (CCN) activation. We simulated nearly 300 scenarios and, through a regression analysis, identified the key parameters driving the value of the aging timescale. We show that the value of the aging timescale spans from hours to weeks, depending on local environmental conditions and characteristics of the fresh BC-containing particles. Although the simulations presented in this study included many processes and particle interactions, through a regression analysis we show that 80% of the variance in the aging timescale is explained by only a few key parameters. The condensation aging timescale decreased with the flux of condensing aerosol and was shortest for the largest fresh particles, while the coagulation aging timescale decreased with the total number concentration of large (D>100 nm), CCN-active particles and was shortest for the smallest fresh particles. Therefore, both condensation and coagulation play important roles in aging, and their relative impact depends on the particle size range.
-
Environmental Sciences Department Seminar
"Fast physics testbed: development, demo, and applications"
Presented by Wuyin Lin, Environmental Sciences Department
Tuesday, July 2, 2013, 11 am
Conference Room, Bldg 815EHosted by: Ernie Lewis
Clouds and their associated physical processes exert strong influences on the climate system through the couplings with dynamical, hydrological and radiative processes. Representation of cloud-related fast physics in climate models however has long been a challenging task, and primarily responsible for the large uncertainty in climate projections. The BNL's Fast-Physics System Testbed and Research (FASTER) project is tasked to develop a comprehensive cloud modeling testbed to enhance and accelerate evaluation and improvement of cloud representation in climate models. In this talk, I will go over the rationales behind the development of the testbed with a focus on the single column model (SCM) testbed. Applications of the online SCM testbed for interactive model evaluation and cloud parameterization development will also be demonstrated.
-
Environmental Sciences Department Seminar
"Temperature Dependent Yields of Minor Mono- and Di- Substituted Carbonyl Compounds from the Oxidation of Isoprene under Near-zero and High NOx Conditions"
Presented by Dr. Ryan Thalman, University of Colorado
Wednesday, June 12, 2013, 11 am
Conference Room, Bldg 815EHosted by: Jian Wang
Isoprene emitted by the biosphere is the largest biogenic portion of the global budget of volatile organic compounds (VOC). Isoprene in the atmosphere is predominantly oxidized by the hydroxyl radical (OH). The oxidation of VOCs in the atmosphere contributes to the creation of ozone and secondary organic aerosol (SOA). Recent theoretical predictions and measurements have shown that small carbonyl compounds such as glyoxal, methyl glyoxal, hydroxyacetone and glycolaldehyde may be produced as co-product pairs from rapid isomerization of peroxy radicals in the first generation of isoprene oxidation. We investigated the temperature (260K, 298K and 330K) and NOx (near-zero NOx and high NOx (ppm level)) dependence of the first generation product yields from these isomerization pathways, and the implications of these findings on our understanding of the oxidation mechanism. Experiments combine the atmospheric simulation chamber at the National Center for Atmospheric Research with the CU Light Emitting Diode Cavity Enhanced Differential Optical Absorption Spectroscopy (CU LED-CE-DOAS) for the detection of glyoxal and methyl glyoxal; as well as Proton Transfer Reaction Mass Spectrometry for the detection of other isoprene oxidation products.
-
ASAP Cross Talks: Presentation Series
"Evaluation of a novel wide size range fast integrated mobility spectrometer & EMPIRE: a nuclear reaction model code for nuclear astrophysics, nuclear data and nuclear physics"
Presented by Michail Pikridas & Annalia Palumbo, BNL
Friday, June 7, 2013, 5 pm
Brookhaven CenterHosted by: BNL ASAP
Come grab a drink at the Brookhaven Center Happy Hour and listen to your colleagues talk about their research at BNL! Location: Brookhaven Center, South Room Evaluation of a novel wide size range fast integrated mobility spectrometer by Michail Pikridas Supervisor: Jian Wang A novel instrument, referred to as the wide size range fast integrated mobility spectrometer (WSR-FIMS), that is capable of measuring aerosol distributions at the nanometer size with high frequency, has been developed and evaluated. The WSR-FIMS sizes particles based on their electrical mobility by applying a non-uniform electric field between two parallel plates. All particles, regardless of their mobility, are simultaneously detected by a fast charge-coupled camera after being grown into super-micrometer droplets and illuminated by a laser sheet. The detected aerosol distribution is a function of the voltage range applied during the separation process. By eliminating the need to scan over the detected distribution the WSR-FIMS' time resolution is dictated only by counting statistics and can be as high as 0.1 s under high concentration or 1 s under most ambient conditions. The high sheath to aerosol flow ratio, 50 under typical conditions, ensures a satisfactory size resolution. Particle losses, which have been characterized, mainly occur at the instrument's inlet during conditioning. Because WSR-FIMS combines high time resolution data with single particle counting is suitable for fast changing aerosol processes such as tailpipe emission or mobile (ground or airborne) monitoring. EMPIRE: a nuclear reaction model code for nuclear astrophysics, nuclear data and nuclear physics by Annalia Palumbo Supervisor: Michal Herman EMPIRE is a nuclear reaction model code whose nuclear physics inputs are mainly taken from the RIPL-3 database
-
BSA Distinguished Lecture
"Research at CERN - From the Highest Energies to the Smallest Particles"
Presented by Rolf-Dieter Heuer, Director-General, CERN, Switzerland
Wednesday, May 1, 2013, 5:30 pm
Berkner Hall AuditoriumHosted by: Peter Wanderer
With the start of the Large Hadron Collider (LHC) at CERN, particle physics entered a new era. The LHC will provide a deeper understanding of the universe and the insights gained could change our view of the world, and the talk will present some of the reasons for the excitement surrounding the LHC. The LHC is expected to yield insights into the origin of mass, the nature of dark matter and into many other key questions. This lecture will address the exciting physics prospects offered by the LHC, present first results, in particular the recent discovery of a new 'Higgs-like' Boson, and also a look forward.
-
Brookhaven Lecture
"484th Brookhaven Lecture: 'Nuclear Weapons Stability or Anarchy in the 21st Century: China-India-Pakistan'"
Presented by Tom Graham, Nonproliferation & National Security Department at Brookhaven Lab
Wednesday, February 20, 2013, 4 pm
Berkner Hall AuditoriumHosted by: Allen Orville
-
Particle Physics Seminar
"IceCube-DeepCore-PINGU: Atmospheric Neutrino Physics at the South Pole"
Presented by D. Jason Koskinen, Penn State University
Thursday, September 6, 2012, 3 pm
Small Seminar Room, Bldg. 510Hosted by: David Jaffe
The IceCube neutrino observatory is entering a new stage of sensitivity to possible high energy astrophysical sources using the traditional array and low energy atmospheric neutrinos in conjunction with the DeepCore sub-array. As a dense in-fill to the IceCube neutrino observatory, DeepCore pushes the neutrino energy sensitivity down to tens of GeV. The added low energy reach and megaton size opens up opportunities to study neutrino oscillations, numu disappearance and possibly nutau appearance, using a massive triggered data set of O(100k) atmospheric neutrinos/year. I will cover the current status of DeepCore neutrino physics analyses as well as possible future extensions designed to resolve the neutrino hierarchy in an initial stage (PINGU) and study proton decay/extra-galactic supernovas in an ambitious second stage (MICA).
-
Physics Colloquium
"Thermalization of the quark-gluon plasma in ultra-relativistc heavy ion collisions"
Presented by Jean-Paul Blaizot, Saclay
Tuesday, August 21, 2012, 3:30 pm
Hamilton Seminar Room, Bldg. 555Hosted by: William Morse
There is robust evidence from RHIC, and now from the LHC, that matter produced in ultra-relativistic heavy ion collisions is (nearly) in local equilibrium. To understand how this is achieved, that is, to understand the detailed mechanisms by which the partonic degrees of freedom of the initial nuclear wave functions get freed and subsequently interact to reach local equilibrium, is a challenging problem. In this talk, after reviewing the empirical evidence, I shall discuss recent progress on various issues related to the thermalization of the quark-gluon plasma.
-
C-AD Accelerator Physics Seminar
""Spin Manipulation with RF Wien Filters 1) Spin Rotation 2) EDM effect""
Presented by Yannis K. Semertzidis, BNL Physics Dept
Friday, August 17, 2012, 4 pm
911B, Rm A202, Large Conference RoomHosted by: Chuyu Liu
Abstract: “RF Wien filters running at a spin resonance don’t influence the particle motion. However, they do influence the particle spins. Depending on their orientation they can be used to rotate (flip) the particle spins from up to down or other desired orientation as any RF-dipole would. Rotating the RF Wien filter around its axis by 90 degrees, it can be used to probe the electric dipole moment of the stored particles in a magnetic ring. I will show how one can study the systematic errors and the strength of the method for both purposes.”
-
RIKEN/BNL Lunch Time Talk
"The Higgs boson mass -- what does it mean for the Standard Model?"
Presented by Fedor Bezrukov, University of Connecticut/RBRC
Thursday, August 16, 2012, 12:30 pm
Building 510 / Room 2-160Hosted by: Tomomi Ishikawa
The Higgs boson with the mass recently announced by the LHC experiments corresponds within current precision to the boundary value between the situations when the electroweak vacuum is stable and metastable. I will discuss the latest developments in the calculation of this boundary mass and importance of measurement of other SM parameters (top quark mass and the strong coupling constant). I will also discuss what is the meaning of this boundary value in various minimal modifications of the Standard Model.
-
Particle Physics Seminar
"Latest SUSY results from ATLAS"
Presented by Nathan Triplett, Brookhaven National Laboratory
Thursday, August 9, 2012, 3 pm
Small Seminar Room, Bldg. 510Hosted by: Marc-Andre Pleier
A search has recently been performed looking for direct pair production of supersymmetric top squarks using the 4.7 fb-1 of data recorded with the ATLAS detector. Results will be shown for analyses with final states containing jets, large missing transverse momentum, and either zero, one, or two isolated leptons.
-
Physics Colloquium
"(Di)photons at the LHC: from precision QCD to searches of new physics"
Presented by David d'Enterria, CERN
Tuesday, August 7, 2012, 3:30 pm
CAD, Building 911B, Large Conference Room # A202Hosted by: Robert Pisarski
Isolated photon and diphoton production in proton-proton (and nucleus-nucleus) collisions provides various "clean" observables for precision QCD studies as well as for new physics searches at the LHC. I will report on the latest experimental measurements at the LHC of (i) isolated-photon pT spectra as a means to constrain the gluon distribution in the proton (and lead nucleus), (ii) diphoton continuum cross sections as a sensitive test of higher-order perturbative QCD corrections, and (iii) diphoton mass distributions from the decay of the Higgs boson and searches of new high-mass states.
-
Particle Physics Seminar
"A Walk on the Dark Side"
Presented by Cristiano Galbiati, Princeton University
Monday, August 6, 2012, 11 am
Small Seminar Room, Bldg. 510Hosted by: Marc-Andre Pleier
There is a wide range of astronomical evidence that the visible stars and gas in all galaxies, including our own, are immersed in a much larger cloud of non-luminous matter, typically an order of magnitude greater in total mass. The existence of this “dark matter†is consistent with evidence from large-scale galaxy surveys and microwave background measurements, indicating that the majority of matter in the universe is non-baryonic. The nature of this non-baryonic component is still totally unknown, and the resolution of the “dark matter puzzle†is of fundamental importance to cosmology, astrophysics, and elementary particle physics. Three major lines of research are directing their efforts at detection of dark matter: the accelerator-based program at the LHC, indirect searches with satellite-born detectors and direct searches with detectors operated in deep underground laboratories. The time is ripe for a discovery, and the new generation of direct searches promises to probe the most interesting region of parameters for the dark matter candidates. I will review and describe the DarkSide underground argon detector at LNGS.
-
C-AD Accelerator Physics Seminar
""Surface Impedance of Superconducting Radio Frequency (SRF) Materials""
Presented by Binping Xiao, CAD BNL
Friday, August 3, 2012, 4 pm
Bldg 911B, Large Conference Rm, Rm A202Hosted by: Chuyu Liu
Abstract: Superconducting radio frequency (SRF) technology is widely adopted in particle accelerators. There remain many open questions, however, in developing a systematic understanding of the fundamental behavior of SRF materials. A facility that can measure the SRF properties of small samples in a range of 2~40 K temperature is needed in order to fully answer these questions. The Jefferson Lab surface impedance characterization (SIC) system has been designed to attempt to meet this requirement. It consists of a sapphire-loaded cylindrical Nb TE011 cavity at 7.4 GHz with a 50 mm diameter flat sample placed on a non-contacting end plate and uses a calorimetric technique to measure the radio frequency (RF) induced heat on the sample. Tests with polycrystalline and large grain bulk Nb samples have been done at <15 mT magnetic field. Microstructure analyses and SRF measurements of large scale epitaxial MgB2 films have been reported. The SRF properties of different film thicknesses (200 nm and 350 nm) were evaluated using SIC system under different temperatures and applied fields at 7.4 GHz. A surface resistance of 9±2 μΩ has been observed at 2.2 K. Based on BCS theory with moving Cooper pairs, the electron states distribution at 0K and the probability of electron occupation with finite temperature have been derived and applied to anomalous skin effect theory to obtain the surface impedance of a superconductor under RF field. We present the numerical results for Nb.
-
Nuclear Physics & RIKEN Theory Seminar
"The azimuthal anisotropy of high P_t hadrons in RHIC and LHC"
Presented by Xilin Zhang, Indiana University
Friday, July 27, 2012, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Bjoern Schenke
In this talk, I will present our study on the azimuthal anisotropy of high p_t particles (from jets) in the relativistic heavy ion collisions, which encode the information about jet energy loss in the medium as well as the medium itself. We focus on three different models with distinctive path-length and matter-density dependence of the energy loss: L^{2}, L^{3}, and near-Tc-enhancement (NTcE). We will first show our simple estimate of jet response to the shape fluctuation of the medium (initial state fluctuation) in the central 200 AGeV Au-Au collision. Second, the MC Glauber model is applied to study different Fourier-harmonics (V_{1,2,3,,,6}) of the final high P_t hadron spectrum in the non-central collisions at both RHIC and LHC (Pb-Pb collision). We find both L^{3} and NTcE can explain V_2 at RHIC (L^{2} underestimates it by roughly 20%), while L^{2} and NTcE are successful at LHC@2.76 TeV (L^{3} overestimates it by roughly 20%). In addition, we see the consistency between our NTcE calculations for other higher harmonics and the LHC@2.76 TeV data. The predictions of these harmonics for LHC@5.5 TeV will also be presented.
-
Condensed-Matter Physics & Materials Science Seminar
"Bounds for the electric potential of water-oil interfaces"
Presented by Mihail Popescu, Ian Wark Research Institute, Univ. of South Australia, Adelaide, Australia
Thursday, July 26, 2012, 1:30 pm
Small Seminar Room, Bldg. 510Hosted by: Antonio Checco
The value of the electric potential (or that of the closely related "zeta"-potential [1]) of a liquid-liquid interface is a crucial parameter for the stability of emulsions, extensively used in the food, cosmetics, or pharmaceutical industries. Because liquid-fluid (i.e., liquid or gas) interfaces are deformable, determining their surface-potential using classic methods designed for solid particles, such as electrophoresis, remains a challenging task. In this work we exploit the spontaneously occurring cascade partial coalescence [2] of a drop of heptol (toluene - n-heptane mixture) rising through water (electrolyte) with a water (electrolyte) - heptol quasi-planar interface, process in which a stable drop emerges as the final state. We discuss how lower- and upper-bounds for the absolute value of the surface potential of these interfaces can be inferred within the limits of the classic DLVO theory [1]. 1. Derjaguin, B. V., Churaev, N. V., and Muller, V. M., "Surface Forces" (Consultants Bureau, New York, 1987). 2. Blanchette, F. and Bigioni, T. P., "Partial coalescence of drops at liquid interfaces", Nat. Phys. 2, 254 (2006).
-
Nuclear Physics & RIKEN Theory Seminar
"Hydrodynamics at large baryon densities: Understanding proton vs. anti-proton $v_2$ and other puzzles"
Presented by Jan Steinheimer-Froschauer, University of Frankfurt/Lawrence Berkeley National Laboratory
Friday, July 20, 2012, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Adam Bzdak
Using hydrodynamics we explore the effects of the initial state, baryon stopping and baryon number transport on various observables such as spectra, elliptic flow and particle yields for heavy ion collisions at beam energies from $\sqrt{s_{NN}}=7.7$ to $200$ GeV. In our setup the transition from the equilibrated hydrodynamical phase to the final transport phase occurs over a broad range of temperatures/densities. Even though particle yields, extracted at this transition, can be described well by a single temperature freeze out we observe a correlation of particle mass, average transition temperature and flow velocity which allows us to successfully describe the measured non-monotonic behavior of the effective slope parameter as a function of particle mass. Furthermore we show that observed phenomena such as the centrality dependent freeze out parameters as well the asymmetry in particle/antiparticle $v_2$ at large baryon densities can be explained by a collective hydrodynamic expansion, once baryon stopping and baryon number conservation are properly taken into account. We will further discuss how the various stages of the collision contribute to the $p_{\bot}$ spectra and the mass dependence of $T_{eff}$.
-
C-AD Accelerator Physics Seminar
""Lengthening the Spin Coherence Time: A Progress Report from COSY""
Presented by Dr. Edward Stephenson, Indiana University
Wednesday, July 18, 2012, 4 pm
Bldg 911B, Rm A202, Large Conf. RmHosted by: Chuyu Liu
Abstract: A requirement for using a storage ring in the search for an electric dipole moment on charged particles is that the beam be polarized along the beam velocity and remain that way for times up to 103 seconds. This seminar will report on progress made in May of this year using a vector polarized, 0.97-GeV/c deuteron beam at the Cooler Synchrotron (COSY) located at the Forschungszentrum-Jülich in Germany to study the evolution of the horizontal-plane polarization under a variety of conditions. Beam polarization measurements were made continuously during the beam store by slowly extracting the beam onto a thick, 1.5-cm target and observing scattered, charged particles in the EDDA scintillator array. Asymmetries in the count rates provided information on the two transverse components of the beam polarization. The polarization was rotated from the vertical (stable) direction into the ring plane using an RF solenoid operated on the 1‒Gγ harmonic of the spin tune frequency. A system was commissioned to time-stamp each polarimeter event so that the revolution of the polarization in the horizontal plane (120 kHz) could be unfolded and measured directly. By the use of electron cooling and selective beam heating through white noise applied to stripline plates, the vertical and horizontal emittances of the beam were adjusted separately. Horizontal polarization measurements showed that the polarization lifetime fell as the square of the width of the horizontal beam profile. By adjusting a family of sextupole magnet currents, it was possible to cancel the spread of the spin tunes responsible for the depolarization and achieve lifetimes of hundreds of seconds. Similar large polarization lifetimes were observed using beam that was continuously electron cooled.
-
Condensed-Matter Physics & Materials Science Seminar
"Raman scattering studies of phonons and magnons in FeSe-based superconductors"
Presented by Qing-Ming Zhang, Department of Physics, Renmin University, Beijing, China
Monday, July 16, 2012, 1:30 pm
Small Seminar Room, Bldg. 510Hosted by: Genda Gu
Newly discovered alkali-metal intercalated FeSe superconductor has a maximum transition temperature of ~31K. About thirteen Raman phonon modes are observed in the new superconductor, much larger than that expected for an ideal BaFe2As2-like structure. We deduce possible forms of Fe-vacancy ordering by careful analysis of polarization and crystal rotations. Most of the Raman modes can be well assigned in combination of first-principles calculations. We further investigate the effect of alkali-metal and Fe substitution on Raman modes. Two-magnon peak is also observed around 200meV in AFe1.6Se2. Interestingly, the intensity of the two-magnon peak falls sharply on entering the superconducting phase, while this effect is completely absent in non-superconducting KFe1.5Fe2. This reveals a strong competition between antiferromagnetism and superconductivity, which may arise from the proximity effect within regions of microscale phase separation.
-
Nuclear Physics & RIKEN Theory Seminar
"More on the string inspired solution to the sign problem and overlapping problem"
Presented by Masanori Hanada, KEK Theory Center
Friday, July 13, 2012, 2 pm
Small Seminar Room, Bldg. 510Hosted by: Bjoern Schenke
The effect of the complex phase of the fermion determinant is a key question related to the sign problem in finite-density QCD. Recently, based on a field-theoretic argument inspired by the string theory, it has been shown that ignoring the complex phase -- the phase quenching -- does not change the expectation values of a class of observables in a certain region of the phase diagram when a number of colors Nc is large. In this talk we briefly explain this equivalence and show that the same equivalence holds in effective models and holographic models. We show, in a unified manner, that the phase quenching gives exact results for a class of fermionic observables (e.g., chiral condensate) in the mean-field approximation and for gauge-invariant gluonic observables (e.g., Polyakov loop) up to one-meson-loop corrections beyond mean field. We also discuss implications for the lattice simulations and confirm good quantitative agreement between our prediction and existing lattice QCD results. Therefore the phase quenching provides rather accurate answer already at Nc=3 with small 1/Nc corrections which can be taken into account by the phase reweighting.
-
RIKEN/BNL Lunch Time Talk
"Evolution of singularities in unequal time correlator in thermalization of strongly coupled gauge theory"
Presented by Shu Lin, RBRC
Thursday, July 12, 2012, 12:30 pm
Building, 510/Room 2-160Hosted by: Tomomi Ishikawa
Thermalization of strongly coupled gauge theory can be described by a gravitational collapse process via gauge/gravity duality. We studied the evolution of unequal time correlator in a gravitational collapse background, which allowed us to probe different stages of thermalization process. We found that the singularities of the correlator are consistent with geometric optics picture in the gravitational collapse background. We found the thermalization is characterized by the disappearance of singularities on real time axis and possible emergence of singularities in complex time plane in the correlator.
-
Instrumentation Division Seminar
"Instrumentation for CMS Experiment Upgrade at Helsinki Institute of Physics"
Presented by Jaakko Härkönen, Helsinki Institute of Physics, Finland
Thursday, July 12, 2012, 11 am
Large Conference Room, Bldg. 535Compact Muon Solenoid (CMS) is one of the four experiments within the CERN Large Hadron Collider. Helsinki Institute of Physics (HIP) CMS group has participated in the construction, testing and commissioning of the CMS silicon tracker for more than a decade. This seminar gives an overview of the instrumentation projects in this group. Radiation hardness of the silicon sensors is one of the main challenges in the scope of future LHC luminosity upgrade. In this presentation special emphasis is put on semiconductor processing techniques, such as Magnetic Czochralski silicon (MCz-Si) and Atomic Layer Deposition (ALD), that enable an order of magnitude better radiation hardness compared to the currently used techniques while being simultaneously cost-effective. Examples of novel detector developments by CERN RD39 Collaboration, low-temperature Current Injected Detector (CID) and cryogenic Beam Loss Monitor (BLM) are presented.
-
Condensed-Matter Physics & Materials Science Seminar
"From YBCO nanowires and Josephson junctions to superconducting hybrids:properties and macroscopic quantun phenoma"
Presented by Francesco Tafuri, CNR-SPIN and Seconda Università di Napoli, ITALY, Italy
Tuesday, July 10, 2012, 2 pm
Bldg. 480 conference roomHosted by: Ivan Bozovic
High critical temperature superconductors (HTS) nano-sized systems ranging from YBaCuO nano-junctions and nano-channels to superconducting hybrid systems incorporating nanowires, have been realized and characterized exhibiting a series of remarkable properties. YBCO nanowires of widths down to 50 nm operate up at 80 K with critical current densities just a few times smaller than the depairing current. Escape dynamics has been measured in top-down and “self-assembling” bottom-up nano-Josephson junctions characterized by different levels of dissipation. By measuring switching process from the zero voltage to the finite voltage branch in the current-voltage (I-V) characteristics, their quantum signature encoded in macroscopic quantum phenomena has been extracted. Novel insights on the interplay between coherence and dissipation in the moderately damped regime have been achieved, of interest for various quantum hybrid architectures. In these junctions phase diffusion processes coexist with thermal activation and macroscopic quantum tunneling. Similar studies have been comparatively carried out on NbN Josephson junctions. Results encourage the integration of HTS nanostructures in hybrid systems functional to various applications and in quantum cells.
-
NSLS-II Seminar
"High Speed Choppers for X-Ray or Light Pulse Selection"
Presented by Bernd Eberhard Lindenau, Forschungszentrum Juelich GmbH ( FZJ ), Central Department of Technology ( ZAT), Magnetic Bearings and Drives, Germany
Monday, July 9, 2012, 1:30 pm
703 Large Conference RoomHosted by: Daniel Bacescu
For experiments, which ask for light pulses with a sequence different from the bunch mode predominantly offered by the synchrotron source, high speed pulse selectors have been developed. A fast rotating triangular shaped disk with the beam channel grooved along one of the disk sides serves as shutter element in the beam line for hard x-rays. The maximum open sequence of about 1000Hz is limited by the tolerable rotation speed of the shutter rotor, which is machined from high strength titanium alloy. Open times of the beam channel in the range of 500ns and +/-2 ns phase stability with respect to the bunch clock are realized with the present systems, which are used in combination with a probing laser for time resolved experiments at ESRF, APS, SPring8 and PF-AR. A 1.25 MHz chopper for light pulses is currently under development for operation at BESSY. It is based on the same platform for magnetic rotor suspension and drive control. This chopper is equipped with a slotted aluminium disk to allow open periods of 140ns. The design criteria of these systems will be presented and technical feasibilities will be addressed.