March 2020
Sunday Monday Tuesday Wednesday Thursday Friday Saturday

1

1. No events scheduled

2

1. No events scheduled

3

1. 11 am, Small Seminar Room, Bldg. 510

Hosted by: Rongrong Ma

The PHENIX experiment operates as one of the major detectors at the RHIC collider to identify and study Quark Gluon Plasma (QGP). Direct photons have long been considered as unique probes to study properties of QGP due to their small interaction cross section with the collision produced medium, hence carrying direct information of their creation point. Taking advantage of the precise tracking system and high granularity electromagnetic calorimeter, PHENIX has made comprehensive measurements of direct photons across different collision species and a wide range of beam energies. In this talk I will show new measurements with high statistics Au+Au data taken in 2014 at 200GeV using the photon conversions at the silicon vertex detector (VTX). This dataset provides a 10-fold increase in statistics for the measurements of direct photon yields and their anisotropy.

4

1. 2:30 pm, Small Seminar Room, Bldg. 510

Hosted by: Peter Denton

We present a novel integrator based on normalizing flows which can be used to improve the unweighting efficiency of Monte-Carlo event generators for collider physics simulations. In contrast to the machine learning approaches based on surrogate models, our method generates the correct result even if the underlying neural networks are not optimally trained. We exemplify the new strategy using the example of Drell-Yan type processes at the LHC.

2. 4 pm, Small Seminar Room, Bldg. 510

Hosted by: Viviana Cavaliere

The Higgs boson discovery at the LHC marked a historic milestone in the study of fundamental particles and their interactions. Over the last eight years, we have begun measuring its properties, which are essential to build a deep understanding of the Higgs sector of the Standard Model and to potentially uncover new phenomena. The Standard Model is far from being a complete theory of nature and many of its predictions have yet to be tested. In particular, the energy potential of the Higgs boson field, responsible for the electroweak symmetry breaking mechanism, has not yet been measured by any experiment. A measurement of the Higgs boson self-coupling at the LHC would shed light into the actual structure of the potential, whose exact shape can have deep theoretical consequences. This coupling can be accessed directly through the very challenging measurement of Higgs pair production. In this talk the experimental status of the di-Higgs boson production searches and constraints on the self-coupling at the LHC will be presented and the special role played by the decay to b-quark, the largest Higgs branching fraction, and its distinctive signature will be described.

5

1. 12 pm, Building 510, Room 2-160

Hosted by: Akio Tomiya

The transverse momentum dependent parton distribution functions (TMDPDFs) measure the transverse momentum of partons in a fast moving hadron, and is an important observable for the Electron-Ion Collider. The energy evolution of TMDPDFs is given by the Collins-Soper (CS) anomalous dimension, or the CS kernel, which is essential to the fitting of TMDPDFs from global cross section data at different energies. At small transverse momentum, the CS kernel is nonperturbative and can only be determined from global fitting or first principle calculations. In this talk, I present an exploratory calculation of the CS kernel from lattice QCD using the large-momentum effective theory, which is a systematic approach to extract light-cone parton physics. Our preliminary results show that it is promising to achieve precision calculation with currently available computing resources, which has the potential to be used in the global fitting of TMDPDFs in the future.

6

1. 12:15 pm, Building 510, Room 2-95

Hosted by: Peter Denton

7

1. No events scheduled

8

1. No events scheduled

9

1. No events scheduled

10

1. 11 am, Small Seminar Room, Bldg. 510

Hosted by: Rongrong Ma

We re-analyze the bremsstrahlung problem in a background field consisting of several sources. We explain how these processes can be represented as a sum of diagrams, generally interfering and thus leading to the well known LPM effect. Then we show how these diagrams can be properly resummed at high energies to go beyond the most common approximations in phenomenological analyses to date: the perturbative (GLV), the Gaussian (BDMPS) or the semi-infinite medium (AMY) approximations. Finally we present some QED and QCD results, and show how the improvement is able to cure some of the puzzles found in data, namely the temperature issues in the determination of the QGP color opacity, encoded usually in the transport coefficient, $\hat{q}$. This finding indicates that full resummations are required for a proper extraction of the QCD matter parameters, and may open up an additional handle on the study of the QCD Equation of State.

2. 3:30 pm, Large Seminar Room, Bldg. 510

Hosted by: Bjoern Schenke

Hard probes such as heavy flavor quarks, jets, and virtual and real photons convey valuable information from the heart of high energy nuclear collisions, opening a window into the microscopic nature of QCD matter. These probes have been used to study both hadronic states and also nuclear matter under extreme conditions. In addition, the spin degree of freedom of the colliding proton provides a fresh perspective on the quantum nature of nuclear matter, enabled by the unique capabilities of RHIC. The rareness of hard probes demands detectors capable of high precision and high rate, which in turn drives the design and the innovation of the next generation of nuclear physics collider experiments, such as sPHENIX and future EIC detectors. I will recount a story told by hard probes of nuclear collisions through selected results from PHENIX, the plans for sPHENIX, and the possibilities at the EIC.

11

1. No events scheduled

12

1. 12 pm, Building 510, Room 2-160

Hosted by: Yuta Kikuchi

Ioffe time essentially quantifies the distance along the lightcone that the quark fields that enter the correlator describing the Parton Distribution Function (PDF) are separated by. In this sense, it is a natural candidate for clearly separating the short and long distance physics. We study how the behavior of the parton distribution in Ioffe time can be mapped out given its Mellin moments. Pseudo PDFs describe the nucleon matrix elements of quark field operators separated by a space like distance z. These are calculable in lattice QCD and as z^2 approaches zero, pseudo PDFs approach the actual PDFs. Complimentary to lattice efforts, we study the behavior of of pseudo PDFs as a function of z in a spectator diquark model. We also extend the study to Generalized Parton Distributions (GPDs), which involves taking into account an extra degree of freedom because of the non diagonal nature of the hadronic matrix element in the case of GPDs.

13

1. 2 pm, Building 510, CFNS Room 2-38

Hosted by: Nikhil Karthik

14

1. No events scheduled

15

1. No events scheduled

16

1. No events scheduled

17

1. No events scheduled

18

1. 1:30 pm, Training Room, Bldg 725

Hosted by: Layla Hormozi

TBA

19

1. No events scheduled

20

1. 10:30 am, web cast

Hosted by: Vladmir Tischenko

The ability of current and next generation accelerator based neutrino oscillation measurements to reach their desired sensitivity requires a high-level of understanding of the neutrino-nucleus interactions. These include precise estimation of the relevant cross sections and the reconstruction of the incident neutrino energy from the measured final state particles. Incomplete understanding of these interactions can skew the reconstructed neutrino spectrum and thereby bias the extraction of fundamental oscillation parameters and searches for new physics. In this talk I will present the first exclusive differential cross section measurement using neutrino-Argon Quasi Elastic like interactions from the MicroBooNE experiment. In addition, using wide phase-space electron scattering data, collected using the CLAS spectrometer at the Thomas Jefferson National Accelerator Facility (JLab), the reconstruction of the incoming lepton energy from the measured final state is being tested. Disagreements with current event generators, used in the analysis of neutrino oscillation measurements, are observed which indicate underestimation of nuclear effects. The impact of these findings on bias in oscillation analyses will be discussed.

21

1. No events scheduled

22

1. No events scheduled

23

1. No events scheduled

24

1. 3 pm, Webcast

Hosted by: Chao Zhang

One of the biggest surprises in particle physics is that the neutrinos have mass, which was discovered by the neutrino oscillation experiments. This fundamental property of neutrinos leads to some new questions. What is the ordering of the neutrino mass states? Do the neutrinos violate the matter/antimatter symmetry? What characteristics does the neutrino mixing matrix have? The Deep Underground Neutrino Experiment (DUNE) will address these questions with the high-precision Liquid Argon Time Projection Chamber (LArTPC) technology. In this talk, I will give a brief overview of neutrino oscillations, then describe DUNE and its physics programs. I will also talk about the Pulsed Neutron Source as an innovative calibration technique for liquid argon TPCs. The precision measurements of the neutrinos will open a window to new physics beyond the standard model. We will discuss the future and prospects of neutrino physics.

25

1. 6:30 pm, Conference Room A, Bldg. 725

Hosted by: Layla Hormozi

TBA

26

1. 3 pm, web cast

Hosted by: George Redlinger

The expected precision of current long-baseline neutrino oscillation experiments (T2K, NOνA) will be limited by uncertainties in neutrino interaction models in addition to sample statistics. The interaction uncertainties will also play a significant role in next-generation experiments (DUNE, Hyper-K), which aim to collect much larger samples of oscillated neutrinos. Without significant advancements in neutrino-nucleus interaction modeling, traditional analyses will be susceptible to biased oscillation measurements. The DUNE-PRISM (Precision Reaction Independent Spectrum Measurement) technique offers a complementary approach to the oscillation analysis methods used by T2K, NOνA, and MINOS. DUNE-PRISM uses direct extrapolation of near detector data to infer oscillation probabilities with significantly less dependence on the validity of neutrino interaction models. This is achieved by combining multiple near detector measurements, each taken with the detector at a different off beam axis position, in order to sample a variety of neutrino energy spectra. This talk will introduce DUNE-PRISM and show how the oscillation parameters extracted using this technique are robust to unknown interaction modeling errors.

27

1. 12:15 pm, Bluejeans

Hosted by: Peter Denton

Bluejeans link is https://bluejeans.com/507765681 Bluejeans: You can call in from the US with: tel:+1.888.748.9073 and the meeting ID is 507 765 681.

28

1. No events scheduled

29

1. No events scheduled

30

1. No events scheduled

31

1. No events scheduled

1. APR

2

Thursday

Particle Physics Seminar

"Neutrino Interactions, the Universe, and Everything"

Presented by Kirsty Duffy, Fermilab

3 pm, Webcast

Thursday, April 2, 2020, 3:00 pm

Hosted by: Elizabeth Worcester

2. APR

2

Thursday

Particle Physics Seminar

"Neutrino Interactions, the Universe, and Everything"

Presented by Kirsty Duffy, Fermi National Laboratory

3 pm, web cast

Thursday, April 2, 2020, 3:00 pm

Hosted by: Elizabeth Worcester

3. APR

7

Tuesday

Particle Physics Seminar

"Three-dimensional approaches to reconstruct neutrino activity for LArTPCs"

Presented by Hanyu Wei, Brookhaven National Laboratory

3 pm, web cast

Tuesday, April 7, 2020, 3:00 pm

Hosted by: Steve Kettell

4. APR

8

Wednesday

CSI Q Seminar

"CANCELLED Quantum-driven classical optimization"

Presented by Helmut Katzgraber, Microsoft Research

1:30 pm, Training Room, Bldg 725

Wednesday, April 8, 2020, 1:30 pm

Hosted by: Layla Hormozi

The advent of the first useful quantum computing devices has resulted in an arms race with classical algorithms on traditional computing hardware. While near-term quantum devices might revolutionize, e.g., optimization and quantum chemistry, tackling many applications will directly depend on either hybrid or purely classical computing techniques. Inspired by these recent exciting developments, a variety of new classical algorithms have emerged. In this talk an overview on quantum inspired methods and their applications is given.

5. APR

9

Thursday

Particle Physics Seminar

"Maximizing the potential of neutrino experiments"

Presented by Philip Rodrigues, University of Oxford

3 pm, Webcast

Thursday, April 9, 2020, 3:00 pm

Hosted by: Hanyu Wei

Present and future neutrino experiments will search for CP violation in the lepton sector, detect neutrinos from a galactic supernova, and search for evidence of sterile neutrinos. I will discuss two strands of work aimed at maximizing the success of these experiments: on DUNE, developing the far detector trigger system is vital to achieving the physics goals of the experiment; while on the SBN project, neutrino cross section uncertainties are a major systematic in the sterile neutrino oscillation analysis.

6. MAY

12

Tuesday

Nuclear Physics Seminar

"Unitarity in meson spectroscopy: implications for experiment, lattice, and models"

Presented by George Rupp, Instituto Superior Técnico

11 am, Small Seminar Room, Bldg. 510

Tuesday, May 12, 2020, 11:00 am

Hosted by: Jin Huang

The most fundamental cornerstone of the PDG tables is the uniqueness of S-matrix pole positions of unstable particles, as a consequence of quantum-field-theory principles. Therefore, the unitarity property of the S-matrix should ideally be respected in whatever description of meson resonances in experiment, lattice-QCD simulations, and quark models. However, mesons are still often analyzed using non-unitary Breit-Wigner parametrizations and treated as manifest bound states on the lattice or in models. In the present talk I shall demonstrate the huge discrepancies that may result from such naive approaches, with potentially dramatic consequences for meson spectroscopy and the inferred confining potential.

7. MAY

12

Tuesday

Physics Colloquium

"TBA"

Presented by Tae Min Hong, University of Pittsburgh

3:30 pm, Large Seminar Room, Bldg. 510

Tuesday, May 12, 2020, 3:30 pm

Hosted by: George Redlinger

8. MAY

15

Friday

NT/RIKEN Seminar

"TBA"

2 pm, Building 510, CFNS Room 2-38

Friday, May 15, 2020, 2:00 pm

Hosted by: Nikhil Karthik

9. MAY

21

Thursday

Particle Physics Seminar

"TBA"

3 pm, Small Seminar Room, Bldg. 510

Thursday, May 21, 2020, 3:00 pm

10. MAY

22

Friday

NT/RIKEN Seminar

"TBA"

Presented by Shohini Bhattacharya, Temple University

2 pm, Building 510, CFNS Room 2-38

Friday, May 22, 2020, 2:00 pm

Hosted by: Nikhil Karthik

11. JUL

17

Friday

NT/RIKEN Seminar

"TBA"

Presented by Asmita Mukharjee, IIT Bombay

2 pm, Building 510, CFNS Room 2-38

Friday, July 17, 2020, 2:00 pm

Hosted by: Nikhil Karthik

1. HET Lunch Seminar

""Physics Opportunities with Potential DUNE Beam Upgrades""

Presented by Mary Bishai (BNL)

Friday, March 27, 2020, 12:15 pm
Bluejeans

Hosted by: Peter Denton

Bluejeans link is https://bluejeans.com/507765681 Bluejeans: You can call in from the US with: tel:+1.888.748.9073 and the meeting ID is 507 765 681.

2. Particle Physics Seminar

"Overcoming Neutrino Interaction Mis-modeling with DUNE-PRISM"

Presented by Luke Pickering, Michigan State University

Thursday, March 26, 2020, 3 pm
web cast

Hosted by: George Redlinger

The expected precision of current long-baseline neutrino oscillation experiments (T2K, NOνA) will be limited by uncertainties in neutrino interaction models in addition to sample statistics. The interaction uncertainties will also play a significant role in next-generation experiments (DUNE, Hyper-K), which aim to collect much larger samples of oscillated neutrinos. Without significant advancements in neutrino-nucleus interaction modeling, traditional analyses will be susceptible to biased oscillation measurements. The DUNE-PRISM (Precision Reaction Independent Spectrum Measurement) technique offers a complementary approach to the oscillation analysis methods used by T2K, NOνA, and MINOS. DUNE-PRISM uses direct extrapolation of near detector data to infer oscillation probabilities with significantly less dependence on the validity of neutrino interaction models. This is achieved by combining multiple near detector measurements, each taken with the detector at a different off beam axis position, in order to sample a variety of neutrino energy spectra. This talk will introduce DUNE-PRISM and show how the oscillation parameters extracted using this technique are robust to unknown interaction modeling errors.

3. CSI Q Seminar

"CANCELLED"

Presented by Evan Philip, Stony Brook University

Wednesday, March 25, 2020, 6:30 pm
Conference Room A, Bldg. 725

Hosted by: Layla Hormozi

TBA

4. Particle Physics Seminar

"Exploring the neutrino physics with the Deep Underground Neutrino Experiment"

Presented by Jingbo Wang, University of California, Davis

Tuesday, March 24, 2020, 3 pm
Webcast

Hosted by: Chao Zhang

One of the biggest surprises in particle physics is that the neutrinos have mass, which was discovered by the neutrino oscillation experiments. This fundamental property of neutrinos leads to some new questions. What is the ordering of the neutrino mass states? Do the neutrinos violate the matter/antimatter symmetry? What characteristics does the neutrino mixing matrix have? The Deep Underground Neutrino Experiment (DUNE) will address these questions with the high-precision Liquid Argon Time Projection Chamber (LArTPC) technology. In this talk, I will give a brief overview of neutrino oscillations, then describe DUNE and its physics programs. I will also talk about the Pulsed Neutron Source as an innovative calibration technique for liquid argon TPCs. The precision measurements of the neutrinos will open a window to new physics beyond the standard model. We will discuss the future and prospects of neutrino physics.

5. Particle Physics Seminar

"Probing ν interactions for ν physics"

Presented by Adi Ashkenazi, MIT

Friday, March 20, 2020, 10:30 am
web cast

Hosted by: Vladmir Tischenko

The ability of current and next generation accelerator based neutrino oscillation measurements to reach their desired sensitivity requires a high-level of understanding of the neutrino-nucleus interactions. These include precise estimation of the relevant cross sections and the reconstruction of the incident neutrino energy from the measured final state particles. Incomplete understanding of these interactions can skew the reconstructed neutrino spectrum and thereby bias the extraction of fundamental oscillation parameters and searches for new physics. In this talk I will present the first exclusive differential cross section measurement using neutrino-Argon Quasi Elastic like interactions from the MicroBooNE experiment. In addition, using wide phase-space electron scattering data, collected using the CLAS spectrometer at the Thomas Jefferson National Accelerator Facility (JLab), the reconstruction of the incoming lepton energy from the measured final state is being tested. Disagreements with current event generators, used in the analysis of neutrino oscillation measurements, are observed which indicate underestimation of nuclear effects. The impact of these findings on bias in oscillation analyses will be discussed.

6. CSI Q Seminar

"CANCELLED"

Presented by Javad Shabani, NYU

Wednesday, March 18, 2020, 1:30 pm
Training Room, Bldg 725

Hosted by: Layla Hormozi

TBA

7. NT/RIKEN Seminar- CANCELLED

"A mode by mode approach to heavy ion collision"

Presented by Eduardo Grossi, SBU

Friday, March 13, 2020, 2 pm
Building 510, CFNS Room 2-38

Hosted by: Nikhil Karthik

8. RIKEN Lunch Seminar

"Ioffe time behavior of PDFs and GPDs"

Presented by Abha Rajan, BNL

Thursday, March 12, 2020, 12 pm
Building 510, Room 2-160

Hosted by: Yuta Kikuchi

Ioffe time essentially quantifies the distance along the lightcone that the quark fields that enter the correlator describing the Parton Distribution Function (PDF) are separated by. In this sense, it is a natural candidate for clearly separating the short and long distance physics. We study how the behavior of the parton distribution in Ioffe time can be mapped out given its Mellin moments. Pseudo PDFs describe the nucleon matrix elements of quark field operators separated by a space like distance z. These are calculable in lattice QCD and as z^2 approaches zero, pseudo PDFs approach the actual PDFs. Complimentary to lattice efforts, we study the behavior of of pseudo PDFs as a function of z in a spectator diquark model. We also extend the study to Generalized Parton Distributions (GPDs), which involves taking into account an extra degree of freedom because of the non diagonal nature of the hadronic matrix element in the case of GPDs.

9. Physics Colloquium

"A tale told by hard probes in high energy nuclear collisions – from PHENIX to sPHENIX and on toward the EIC"

Presented by Jin Huang, BNL

Tuesday, March 10, 2020, 3:30 pm
Large Seminar Room, Bldg. 510

Hosted by: Bjoern Schenke

Hard probes such as heavy flavor quarks, jets, and virtual and real photons convey valuable information from the heart of high energy nuclear collisions, opening a window into the microscopic nature of QCD matter. These probes have been used to study both hadronic states and also nuclear matter under extreme conditions. In addition, the spin degree of freedom of the colliding proton provides a fresh perspective on the quantum nature of nuclear matter, enabled by the unique capabilities of RHIC. The rareness of hard probes demands detectors capable of high precision and high rate, which in turn drives the design and the innovation of the next generation of nuclear physics collider experiments, such as sPHENIX and future EIC detectors. I will recount a story told by hard probes of nuclear collisions through selected results from PHENIX, the plans for sPHENIX, and the possibilities at the EIC.

10. Nuclear Physics Seminar

"Jet quenching tests of the QCD Equation of State"

Presented by Xabier Feal, BNL

Tuesday, March 10, 2020, 11 am
Small Seminar Room, Bldg. 510

Hosted by: Rongrong Ma

We re-analyze the bremsstrahlung problem in a background field consisting of several sources. We explain how these processes can be represented as a sum of diagrams, generally interfering and thus leading to the well known LPM effect. Then we show how these diagrams can be properly resummed at high energies to go beyond the most common approximations in phenomenological analyses to date: the perturbative (GLV), the Gaussian (BDMPS) or the semi-infinite medium (AMY) approximations. Finally we present some QED and QCD results, and show how the improvement is able to cure some of the puzzles found in data, namely the temperature issues in the determination of the QGP color opacity, encoded usually in the transport coefficient, $\hat{q}$. This finding indicates that full resummations are required for a proper extraction of the QCD matter parameters, and may open up an additional handle on the study of the QCD Equation of State.

11. HET Lunch Discussion

"Windows into the Muon HVP from Staggered Lattice QCD"

Presented by Aaron Meyer, BNL

Friday, March 6, 2020, 12:15 pm
Building 510, Room 2-95

Hosted by: Peter Denton

12. RIKEN Lunch Seminar

"Nonperturbative Collins-Soper Kernel from Lattice QCD"

Presented by Yong Zhao, BNL

Thursday, March 5, 2020, 12 pm
Building 510, Room 2-160

Hosted by: Akio Tomiya

The transverse momentum dependent parton distribution functions (TMDPDFs) measure the transverse momentum of partons in a fast moving hadron, and is an important observable for the Electron-Ion Collider. The energy evolution of TMDPDFs is given by the Collins-Soper (CS) anomalous dimension, or the CS kernel, which is essential to the fitting of TMDPDFs from global cross section data at different energies. At small transverse momentum, the CS kernel is nonperturbative and can only be determined from global fitting or first principle calculations. In this talk, I present an exploratory calculation of the CS kernel from lattice QCD using the large-momentum effective theory, which is a systematic approach to extract light-cone parton physics. Our preliminary results show that it is promising to achieve precision calculation with currently available computing resources, which has the potential to be used in the global fitting of TMDPDFs in the future.

13. Particle Physics Seminar

"What is the Higgs boson hiding"

Presented by Caterina Vernieri, SLAC National Accelerator Laboratory

Wednesday, March 4, 2020, 4 pm
Small Seminar Room, Bldg. 510

Hosted by: Viviana Cavaliere

The Higgs boson discovery at the LHC marked a historic milestone in the study of fundamental particles and their interactions. Over the last eight years, we have begun measuring its properties, which are essential to build a deep understanding of the Higgs sector of the Standard Model and to potentially uncover new phenomena. The Standard Model is far from being a complete theory of nature and many of its predictions have yet to be tested. In particular, the energy potential of the Higgs boson field, responsible for the electroweak symmetry breaking mechanism, has not yet been measured by any experiment. A measurement of the Higgs boson self-coupling at the LHC would shed light into the actual structure of the potential, whose exact shape can have deep theoretical consequences. This coupling can be accessed directly through the very challenging measurement of Higgs pair production. In this talk the experimental status of the di-Higgs boson production searches and constraints on the self-coupling at the LHC will be presented and the special role played by the decay to b-quark, the largest Higgs branching fraction, and its distinctive signature will be described.

14. HET Seminar

"Teaching a Computer to Integrate"

Presented by Christina Gao, Fermilab

Wednesday, March 4, 2020, 2:30 pm
Small Seminar Room, Bldg. 510

Hosted by: Peter Denton

We present a novel integrator based on normalizing flows which can be used to improve the unweighting efficiency of Monte-Carlo event generators for collider physics simulations. In contrast to the machine learning approaches based on surrogate models, our method generates the correct result even if the underlying neural networks are not optimally trained. We exemplify the new strategy using the example of Drell-Yan type processes at the LHC.

15. Nuclear Physics Seminar

"Direct Photon Production in Au+Au collisions at 200GeV"

Presented by Wenqing Fan, Stony Brook University

Tuesday, March 3, 2020, 11 am
Small Seminar Room, Bldg. 510

Hosted by: Rongrong Ma

The PHENIX experiment operates as one of the major detectors at the RHIC collider to identify and study Quark Gluon Plasma (QGP). Direct photons have long been considered as unique probes to study properties of QGP due to their small interaction cross section with the collision produced medium, hence carrying direct information of their creation point. Taking advantage of the precise tracking system and high granularity electromagnetic calorimeter, PHENIX has made comprehensive measurements of direct photons across different collision species and a wide range of beam energies. In this talk I will show new measurements with high statistics Au+Au data taken in 2014 at 200GeV using the photon conversions at the silicon vertex detector (VTX). This dataset provides a 10-fold increase in statistics for the measurements of direct photon yields and their anisotropy.

16. NT/RIKEN Seminar

"Studying supranuclear matter with gravitational waves from neutron star binaries"

Presented by Katerina Chatziioannou

Friday, February 28, 2020, 2 pm
Building 510, CFNS Seminar Room 2-38

Hosted by: Nikhil Karthik

17. HET Lunch Discussion

"LMA-Dark: Large New Physics Effects in Neutrino Oscillations"

Presented by Peter Denton, BNL

Friday, February 28, 2020, 12:15 pm
Building 510, Room 3-192

18. Particle Physics Seminar

"HUNTER: a search for keV-scale sterile neutrinos using trapped atoms"

Presented by Prof. Peter Meyers

Wednesday, February 26, 2020, 3 pm
Small Seminar Room, Bldg. 510

Hosted by: Hanyu Wei

The HUNTER experiment is a search for sterile neutrinos with masses in the 10-300 keV range. The neutrino missing mass will be reconstructed from 131-Cs electron capture decays occurring in a magneto-optically trapped, laser-cooled sample. Reaction-microscope spectrometers will be used to measure the vector momenta of all charged decay products with high solid angle acceptance, and LYSO scintillators read out by silicon photomultiplier arrays detect x-rays, each with sufficient resolution to reconstruct the neutrino missing mass as a peak separated from the near-zero-mass active neutrinos. The stand-alone apparatus to do this has dimensions of a few meters.

19. HET Seminar - Joint BNL/YITP Seminar (at BNL)

"Anomaly free Froggatt-Nielsen models of flavor"

Presented by Jure Zupan, University of Cincinnati

Wednesday, February 26, 2020, 1:30 pm
Small Seminar Room, Bldg. 510

20. Physics Colloquium

"From actions to answers: flavour physics from lattice gauge theory"

Presented by Peter Boyle, BNL

Tuesday, February 25, 2020, 3:30 pm
Large Seminar Room, Bldg. 510

Hosted by: Hooman Davoudiasl

Lattice gauge theory is a numerical approach to the Feynman path integral, and is the only systematically improvable approach to make theoretical predictions of hadronic properties from the underlying theory of quarks and gluons. I will present theoretical numerical calculations of hadronic properties that represent theoretical input to flavour physics, quark flavour mixing, and standard model CP violation in the Kaon, D and B mesons. These lead to constraints on CKM flavour mixing constants of the standard model, and searches for new physics.

21. Nuclear Physics Seminar

"Balance function as a unique probe to the quark gluon plasma: overview and outlook"

Presented by Jin Jin Pan, Wayne State University

Tuesday, February 25, 2020, 11 am
Small Seminar Room, Bldg. 510

Hosted by: Jiangyong Jia

In relativistic heavy-ion collisions, correlations of hadrons with opposite quantum numbers provide insight into general charge creation mechanisms, the time scales of quark production, collective motion of the Quark Gluon Plasma (QGP), and re-scattering in the hadronic phase. The longitudinal and azimuthal widths of general charge balance functions for charged pion (??±), kaon (??±) and (anti-)proton (??/??¯) are used to examine the two-wave quark production scenario recently proposed to explain quark-antiquark productions within the QGP, which predicts a large increase in up and down quark pairs relative to strange quark pairs around the time of hadronization. Balance function as a function of relative azimuthal angle is a good probe to the diffusion effect, which is a signature of the QGP. In addition, the balance function integrals measure hadron pairing probabilities, which provide a key constraint for hadron productions in models. Furthermore, balance function is also a key observable to study net-proton fluctuations and the Chiral Magnetic Effect (CME). In this talk, I will present a state-of-the-art overview on experimental measurements of balance function by STAR and ALICE, along with an outlook for the future experimental measurements.

22. Condensed-Matter Physics & Materials Science Seminar

"Tuning of spin-orbital interactions and charge gap by epitaxial strain in Sr2IrO4"

Presented by Thorsten Schmitt, Photon Science Division, Paul Scherrer Institut, Switzerland

Monday, February 24, 2020, 1:30 pm
ISB Bldg. 734, Conf. Rm. 201 (upstairs)

Hosted by: Mark Dean

The nature of the highly spin-orbit coupled Mott state of Sr2IrO4 suggests the ground state as well as the collective entangled spin and orbital excitations to be strongly dependent on the lattice degree of freedom. For this reason, Sr2IrO4 provides an ideal platform for controlling the physical properties of a correlated material by inducing local lattice distortions. We use epitaxial strain to modify the Ir-O bond geometry and perform momentum-dependent Resonant Inelastic X-ray Scattering (RIXS) both at the metal and ligand sites to unveil the response of the low energy elementary excitations. By applying tensile strain, we observe a large softening of the spin(-orbital) wave dispersion along the [h,0] direction and a simultaneous hardening along the [h,h] direction. This evolution entails a strain-driven crossover from anisotropic to isotropic interactions between the magnetic moments. We also show how the charge excitations are coupled to the lattice in Sr2IrO4. To this end, using O K-edge RIXS, we unveil the evolution of a dispersive electron-hole pair excitonic mode which shifts to lower (higher) energies upon compressive (tensile) strain, manifesting a reduction (increase) in the size of the charge gap. We show that this behavior originates in the modified hopping elements between the t2g orbitals induced by strain. Our work highlights the central role played by the lattice in determining both the spin(-orbital) as well as the charge excitations of Sr2IrO4 and confirms epitaxial strain as a promising route towards the control of the ground state of complex oxides in the presence of high spin-orbit coupling.

23. Condensed-Matter Physics & Materials Science Seminar

"Field-theoretical approach to strongly-correlated problems: RIXS in metals and Spin fermion model"

Presented by Igor Tupitsyn, University of Massachusetts Amherst

Monday, February 24, 2020, 11 am
ISB Bldg. 734 Conf. Rm. 201 (upstairs)

Hosted by: Alexei Tsvelik

In this talk I am going to touch two interesting strongly-correlated problems: Resonant inelastic x-ray scattering (RIXS) in metals and Spin fermion (SF) model. RIXS is a very promising technique for studying collective excitations in condensed matter systems. However, extraction of information from the RIXS signal is a difficult task and the standard approach to solution of RIXS problem is based on approximations that are inaccurate in metals (short-range/contact potentials and non-interacting Fermi-sea). Simultaneously, the SF model has a wide range of applications in the physics of cuprates and iron-based superconductors. However, all developments and applications of the SF model are also based on various, often uncontrollable, approximations. In my talk I am going to address both problems within the general "field-theoretical approach to strongly-correlated problems" framework. In the first part I will consider the RIXS in metals problem within a diagrammatic approach that fully respects the long-range Coulomb nature of interactions between all charged particles. In particular, I will demonstrate how the single-plasmon dispersion can be extracted from the multi-excitation RIXS spectra. In the remaining time I will briefly discuss how to deal with the SF model in the approximation-free manner by employing the Diagrammatic Monte Carlo technique, combining the advantages of Feynman diagrammatic techniques and Quantum Monte Carlo simulations. I will also show what one can get in the first skeleton order – in the widely used in materials science GW approximation.

24. NT/RIKEN Seminar

"Soft Fragmentation on the Celestial Sphere"

Presented by Duff Neill

Friday, February 21, 2020, 2 pm
Building 510, CFNS Room 2-38

Hosted by: Nikhil Karthik

We develop two approaches to the problem of soft fragmentation of hadrons in a gauge theory for high energy processes. The first approach directly adapts the standard resummation of the parton distribution function's anomalous dimension (that of twist-two local operators) in the forward scattering regime, using kT-factorization and BFKL theory, to the case of fragmentation function by exploiting the mapping between the dynamics of eikonal lines on transverse-plane to the celestial-sphere. Critically, to correctly resum the anomalous dimension of the fragmentation function under this mapping, one must pay careful attention to the role of regularization, despite the manifest collinear or infra- red finiteness of the BFKL equation. The anomalous dependence on energy in the celestial case, arising due to the mismatch of dimensionality between positions and angles, drives the differences between the space-like and time-like anomalous dimension of parton densities, even in a conformal theory. The second approach adapts an angular-ordered evolution equation, but working in 4 − 2epsilon dimensions at all angles. The two approaches are united by demanding that the anomalous dimension in 4 − 2epsilon dimensions for the PDF determines the kernel for the angular-ordered evolution to all orders.

25. HET Lunch Discussion

"Multigrid for chiral fermions"

Presented by Peter Boyle, BNL

Friday, February 21, 2020, 12:15 pm
Building 510, Room 1-224

26. NSLS-II Friday Lunchtime Seminar

"Effect of Metal (Pt, Ir) Nuclearity in the Subnanometer Regime on CO Oxidation Activity"

Presented by Ayman M. Karim, Department of Chemical Engineering, Virginia Polytechnic Institute and State University

Friday, February 21, 2020, 12 pm
NSLS-II Bldg. 743 Room 156

Hosted by: Ignace Jarrige

Supported noble metal catalysts are extensively used in industry and their catalytic performance is strongly affected by particle size and shape. In the last decade, supported single atoms and clusters in the subnanometer size regime have attracted a lot of interest since they maximize the metal utilization and have also shown extraordinary catalytic properties for many reactions. However, to tailor the catalyst properties for specific reactions and determine possible limitations, there is a need to understand, on the atomic scale, the origin of reactivity in the subnanometer regime. In this seminar, I will present my group's efforts in understanding the role of metal nuclearity and electronic properties in catalyzing CO oxidation as a model reaction. Using a suite of advanced characterization techniques (aberration-corrected electron microscopy, microcalorimetry, in-situ and in-operando DRIFTS, XPS, EXAFS and HERFD-XANES) complemented by DFT calculations and detailed kinetics measurements, the catalyst structural and electronic properties are identified and correlated with the reaction kinetics. In the talk, CO oxidation on Ir and Pt single atoms and subnanometer clusters supported on MgAl2O4 and CeO2, respectively, will be presented. We identified the active Ir and Pt single atom complexes and show that the reaction follows a combination of Eley-Rideal and Mars-van Krevelen mechanisms. Moreover, we show that despite considered a non-reducible support, CO oxidation on MgAl2O4 supported Ir subnanometer clusters follows a similar mechanism as on a reducible oxide where O2 is activated at the metal-support interface. Finally, the role of metal-support interaction in O2 activation and effect of CO binding strength on the catalytic activity will be discussed.

27. Particle Physics Seminar

"Precision neutrino oscillation physics and DUNE"

Presented by Callum Wilkinson, University of Bern

Thursday, February 20, 2020, 3 pm
Small Seminar Room, Bldg. 510

Hosted by: Hanyu Wei

Neutrino oscillations have been established as an energy and distance dependent phenomena, beyond the Standard Model of Particle Physics. However, a number of key questions remain, which have implications for our understanding of the origin and development of our Universe. The Deep Underground Neutrino Experiment (DUNE), which is currently in the planning stage, has the potential to answer these outstanding questions and make measurements of the other parameters with unprecedented precision. This talk gives an overview of the DUNE sensitivity to oscillation parameters, and describes a program of research aimed at reducing systematic uncertainties, and achieving DUNE's physics goals.

28. RIKEN Lunch Seminar

"Phase Transitions of Quantum Annealing and Quantum Chaos"

Presented by Dr Kazuki Ikeda, Osaka University

Thursday, February 20, 2020, 12 pm
Building 510, Room 1-224

Hosted by: Akio Tomiya

It is known that quantum phase transitions occur in the process of quantum annealing. The order of phase transition and computational efficiency are closely related with each other. Quantum computation starts with a non-entangled state and evolves into some entangled states, due to many body interactions and the dynamical delocalization of quantum information over an entire system's degrees of freedom (information scrambling). It is common to diagnose scrambling by observing the time evolution of single qubit Pauli operators with an out-of-timeorder correlator (OTOC). We aim at establishing a method to clarify those relations between phase transitions and scrambling by OTOCs. Using the p-spin model, we diagnose quantum phase transitions associated with quantum annealing and reverse annealing. In addition we provide a novel Majorana fermion model in which non-stoquastic dynamics of annealing can turn a first-order phase transition into a second-order phase transition. We also show that these phase transitions can be diagnosed by the OTOCs.

29. HET Seminar

"Status of muon g-2 theory"

Presented by Christoph Lehner, BNL

Wednesday, February 19, 2020, 2:30 pm
Small Seminar Room, Bldg. 510

Hosted by: Peter Denton

30. Special NT/RIKEN Seminar

"Infrared gluon mass and the Gribov-Zwanziger model of nonperturbative Yang-Mills theories"

Presented by Leticia Palhares

Wednesday, February 19, 2020, 2 pm
Building 510, CFNS Room 2-38

Hosted by: Nikhil Karthik

In this talk we review indications of an infrared gluon mass in different nonperturbative approaches and discuss its dynamical generation in a Gribov-Zwanziger model. We compute in particular the one-loop effective potential of the model in the recently-established BRST-invariant setup which guarantees gauge-parameter independence of the generated mass scales.

31. Special NT/RIKEN Seminar

"Critical dynamics from small, noisy, fluctuating systems"

Presented by Eduardo Fraga

Tuesday, February 18, 2020, 1 pm
Building 510, CFNS Room 2-38

Hosted by: Nikhil Karthik

Current heavy-ion collision experiments might lead to the discovery of a first-order chiral symmetry breaking phase-transition line, ending in a second-order critical point. Nevertheless, the extraction of information about the equilibrium thermodynamic properties of baryonic matter from the highly dynamic, small, noisy and fluctuating environment formed in such collisions is an extremely challenging task. We address some of the limitations present in the experimental search for the QCD critical point.

32. NT/RIKEN Seminar

"Solving the medium-induced gluon radiation spectrum for an arbitrary number of scatterings"

Presented by Carlota Andres Casas

Friday, February 14, 2020, 2 pm
Building 510, CFNS Seminar Room 2-38

Hosted by: Nikhil Karthik

New measurements of jet quenching observables at RHIC and at the LHC, such as jet substructure observables, demand an increased precision in the theory calculations describing medium-induced radiation of gluons. Closed expressions for the gluon spectrum including an arbitrary number of multiple scatterings have been known for the past 20 years, but analytical calculations have failed to evaluate this spectrum using realistic models for parton-medium interactions. We show a flexible method which allows us to write the analytical expressions for the full in-medium spectrum, including the resummation of all multiple scatterings, in a form where the numerical evaluation can be easily performed without the need of the usually employed harmonic or first opacity approximation. We present the transverse momentum and energy-dependent medium-induced gluon emission distributions for known realistic interaction models to illustrate how our framework can be applied beyond the limited kinematic regions of previous calculations.

33. HET Lunch Discussion

"Simulating Neutrino Physics for JUNO"

Presented by Rebekah Pestes, Virginia Tech

Friday, February 14, 2020, 12:15 pm
Building 510, Room 2-160

34. RIKEN Lunch Seminar

"Shedding light on photon and dilepton spectral functions"

Presented by Greg Jackson, University of Bern

Thursday, February 13, 2020, 12 pm
Building 510, Room 2-160

Hosted by: Yuta Kikuchi

Photons and dileptons offer themselves as 'clean' probes of the quark-gluon plasma because they are unlikely to reinteract once produced. Their emission rates are given via the vector channel spectral function, an object that can ultimately be reconstructed by analytic continuation of lattice data. To confront perturbative results with that data, the NLO corrections are needed in all domains that affect the associated imaginary-time correlator, namely for energies above, below and in the vicinity of the light cone. We summarize recent progress here and, to control an unavoidable snag, we also determine these corrections for the transverse and longitudinal polarizations separately. Our results should help to scrutinize direct spectral reconstruction attempts from lattice QCD.

35. HET Seminar

"BBN and CMB bounds on hidden sector vectors"

Presented by Graham White, TRIUMF

Wednesday, February 12, 2020, 2:30 pm
Small Seminar Room, Bldg. 510

Hosted by: Rob Pisarski

New dark vector bosons that couple very feebly to regular matter can be produced in the early universe and decay after the onset of Big Bang Nucleosynthesis (BBN) or the formation of the cosmic microwave background (CMB) at recombination. The energy injected by such decays can modify the light element abundances or modify the power and frequency spectra of the CMB. In this work we study the constraints implied by these considerations on a range of sub-GeV dark vectors including the kinetically mixed dark photon, as well as gauge B-L and lepton families. We focus on the effects of electromagnetic energy injection, and we update previous investigations of the dark photon by taking into account non-universality in the photon cascade spectrum relevant for BBN and the energy dependence of the ionization eciency after recombination in our treatment of modications to the CMB.

36. Physics Colloquium

"What ever happened to the WIMP of tomorrow?"

Presented by Philip 'Flip' Tanedo, UC Riverside

Tuesday, February 11, 2020, 3:30 pm
Large Seminar Room, Bldg. 510

Hosted by: Gopolang Mohlabeng

The overwhelming observational evidence for the existence of dark matter is only matched by the awkward scarcity of information about what it might actually be. Laboratory searches for dark matter now appear to exclude many of the "weakly interacting massive particle" models that were favored by particle physicists for decades. Where does that leave the hunt for dark matter? If we've left the WIMP behind, what are we looking for? We give a brief, biased, and largely fictional history of the WIMP in order to establish what has and has not been excluded, and why it matters. This general-interest presentation grew out of discussions with astronomers who wanted to understand why some of their particle physics colleagues are "searching for WIMPs" while the others have decided to live in a "post-WIMP world".

37. Nuclear Physics Seminar

"Heavy flavor physics from ATLAS"

Presented by Qipeng Hu, University of Colorado at Boulder

Tuesday, February 11, 2020, 11 am
Small Seminar Room, Bldg. 510

Hosted by: Jiangyong Jia

In A+A collisions, heavy-flavor (charm and bottom) quarks are created at the initial stage of the collision and experience the entire QGP evolution. Therefore, they serve as penetrating probes that traverse the hot and dense medium, interact with the partonic constituents of the plasma and lose energy. Studies of production rate and azimuthal anisotropy of heavy-flavor hadrons provide insight into the energy loss mechanism and transport properties of heavy quarks in the QGP. To better understand the baseline of heavy quark—QGP interaction and the origin of the azimuthal anisotropy, it's crucial to extend the heavy-flavor measurements to smaller systems like p+Pb and pp collisions. In this seminar, selected results on the production and azimuthal anisotropy of the muons from charm and bottom hadron decays in pp, p+Pb and Pb+Pb collisions with the ATLAS experiments at the LHC will be shown. The implications for our understanding of the QGP properties by comparing the results with model calculations will be discussed.

38. HET Special Seminar

"Direct Detection with Relativistic Electrons in Neutron Stars"

Presented by Flip Tanedo, UC Riverside

Monday, February 10, 2020, 3:30 pm
Small Seminar Room, Bldg. 510

Hosted by: Gopolang Mohlabeng

39. Special NT/RIKEN Seminar

"Partonic structure of the proton from large momentum effective theory"

Presented by Xiangdong Ji

Monday, February 10, 2020, 2 pm
Building 510, CFNS Room 2-38

Hosted by: Nikhil Karthik

40. NT/RIKEN Seminar

"New tools for the quantum many-body problem"

Presented by Dean Lee

Friday, February 7, 2020, 2 pm
Building 510, CFNS Seminar Room 2-38

Hosted by: Nikhil Karthik

I discuss three new methods for the quantum many-body problem. The first is the pinhole trace algorithm for first principles calculations of nuclear thermodynamics. I will present lattice Monte Carlo results for the liquid-vapor critical point. The second is the eigenvector continuation method for extrapolation and interpolation of quantum wave functions. I will show how it can be used as a fast emulator for quantum many-body calculations and as a resummation method for divergent perturbative expansions. The third is the projected cooling algorithm for quantum computers. This method is able to construct the localized ground state of any Hamiltonian with a translationally-invariant kinetic energy and interactions that vanish at infinity.

41. HET Lunch Discussion

"Hunting for Dark Matter from the Laboratory to the Cosmos"

Presented by Gopolang Mohlabeng, BNL

Friday, February 7, 2020, 12:15 pm
Building 510, Room 2-160

42. Condensed-Matter Physics & Materials Science Seminar

"Emergent phenomena from disorder on a 3D Topological Insulator surface"

Presented by Yishuai Xu, New York University

Friday, February 7, 2020, 11 am
ISB Bldg. 734, Conf. Rm. 201 (upstairs)

Hosted by: Mark Dean

Three-dimensional topological insulators are bulk insulators with Z2 topological order that gives rise to Dirac surface states. These surface states are well protected against weak perturbations that do not break time-reversal symmetry, such as non-magnetic scalar potential disorder. However recent studies have shown that non-magnetic point defects can introduce new in-gap states. We developed a numerical model to simulate point defects on a TI surface, and performed linear-dichroic angle resolved photoemission (ARPES) to image these states in the surface electronic structure. We find that resonance states associated with the defects can hybridize with the Dirac cone surface state and create a kink-like feature in the band structure near the Dirac point. These resonance states are not Anderson localized even though they cluster around the defects sites, and at higher densities, the kink feature is predicted to evolve into a new distinct band that can support diffusive transport. We also present ARPES spectromicroscopy measurements that more clearly resolve the interplay of Dirac surface states with real-space structure.

43. Condensed-Matter Physics & Materials Science Seminar

"RIXS study of charge dynamics in cuprates"

Presented by Jiaqi Lin, Chinese Academy of Sciences / BNL

Thursday, February 6, 2020, 11 am
ISB Bldg. 734, Conf. Rm. 201 (upstairs)

Hosted by: Mark Dean

The charge dynamics in cuprates is not comprehensively studied due to the limitation of experimental methods. Resonant inelastic x-ray scattering (RIXS) is a technique that is capable of coupling to various types of excitations and recently has been established as a new way to probe charge density response. Here we use RIXS technique to study two types of charge excitations, the plasmon excitations in electron-doped cuprates and the charge density wave (CDW) excitations in hole-doped cuprates. 1) We track the doping dependence of charge excitations in electron-doped cuprates La2-xCexCuO4. From the resonant energy dependence and the out-of-plane momentum dependence, the charge excitations are identified as three-dimensional plasmons, which reflect the nature of the electronic structure and Coulomb repulsion on both short and long length scale. With increasing electron doping, the plasmon excitations increase monotonically in energy and life time, which reflects the reduction of short-range electronic correlation. 2) We report a comprehensive RIXS study of La2−xSrxCuO4 finding that CDW effects persist up to a remarkably high doping level of x = 0.21 before disappearing at x = 0.25. The inelastic excitation spectra remain essentially unchanged with doping despite crossing a topological transition in the Fermi surface. This indicates that the spectra contain little or no direct coupling to electronic excitations near the Fermi surface, rather they are dominated by the resonant cross-section for phonons and CDW-induced phonon-softening. We interpret our results in terms of a CDW that is generated by strong correlations and a phonon response that is driven by the CDW-induced modification of the lattice.

44. HET Seminar

"New Insights on the Short Baseline Neutrino Anomalies"

Presented by Pedro Machado, FNAL

Wednesday, February 5, 2020, 2:30 pm
Small Seminar Room, Bldg. 510

45. Physics Colloquium

"New opportunities in neutrino physics"

Presented by Pedro Machado, Fermilab

Tuesday, February 4, 2020, 3:30 pm
Large Seminar Room, Bldg. 510

Hosted by: Peter Denton

In this colloquium I will briefly review the current status of neutrino physics and I will present new opportunities that will be unfolded by the future neutrino program. Some of these opportunities are incremental over past ones, while others are genuinely new. I will also emphasize the interplay between neutrino and other sectors in probing physics beyond the standard model.

46. Nuclear Physics Seminar

"Global and local polarization of Lambda hyperons in Au+Au collisions"

Presented by Takafumi Niida

Tuesday, February 4, 2020, 11 am
Small Seminar Room, Bldg. 510

Hosted by: Rongrong Ma

The matter created in non-central heavy-ion collisions is expected to have an initial angular momentum carried by two colliding nuclei. Such an initial angular momentum would be transferred to the global polarization due to the spin-orbit coupling. The STAR Collaboration observed \Lambda global polarization in Au+Au collisions at \sqrt{s_{NN}} = 7.7—200 GeV, indicating a thermal vorticity of the system. The detailed structure of the vorticity field may be complicated. Local vorticity and consequently the particle polarization may arise from jets and/or collective flow. In this talk, recent results on the polarization along the beam direction expected from the elliptic flow will be presented and the physics implications will be discussed with theoretical calculations.

47. HET Seminar

"Phase transitions in the early Universe"

Presented by Djuna Croon, TRIUMF

Thursday, January 30, 2020, 2:30 pm
Small Seminar Room, Bldg. 510

In anticipation of the next generation of gravitational wave experiments, I will discuss the opportunities for phenomenological studies of particle physics in the Early Universe. The focus of the talk will be on first order phase transitions in confining gauge theories. Such phase transitions may play an important role in explanations of the strong CP-problem, as well as in models of baryogenesis. I will discuss several such examples and their phenomenology.

48. RIKEN Lunch Seminar - CANCELLED

"TBA"

Presented by Yong Zhao, Brookhaven National Laboratory

Thursday, January 30, 2020, 12 pm
Building 510, Room 3-191

49. Condensed-Matter Physics & Materials Science Seminar

"Effect of Zeeman coupling on the Majorana vortex modes in iron-based topological superconductors"

Presented by Pouyan Ghaemi, The City College of New York

Tuesday, January 28, 2020, 1:30 pm
ISB Bldg. 734, Conf. Rm. 201 (upstairs)

Hosted by: Peter D. Johnson

In the superconducting regime of FeTe(1−x)Sex, there exist two types of vortices which are distinct by the presence or absence of zero energy states in their core. To understand their origin,we examine the interplay of Zeeman coupling and superconducting pairings in three-dimensional metals with band inversion. Weak Zeeman fields are found to suppress the intra-orbital spin-singlet pairing, known to localize the states at the ends of the vortices on the surface. On the other hand, an orbital-triplet pairing is shown to be stable against Zeeman interactions, but leads to delocalized zero-energy Majorana modes which extend through the vortex. In contrast, the finite-energy vortex modes remain localized at the vortex ends even when the pairing is of orbital-triplet form. Phenomenologically, this manifests as an observed disappearance of zero-bias peaks within the cores of vortices upon increase of the applied magnetic field. The presence of magnetic impurities in FeTe(1−x)Sex, which are attracted to the vortices, would lead to such Zeeman-induced delocalization of Majorana modes in a fraction of vortices that capture a large enough number of magnetic impurities. Our results provide a possible explanation to the dichotomy between topological and non-topological vortices recently observed in FeTe(1−x)Sex.

50. HET Seminar

"New physics in rare decays"

Presented by Julian Heeck, UC Irvine

Monday, January 27, 2020, 2:30 pm
Small Seminar Room, Bldg. 510

Despite its many successes, the Standard Model of particle physics cannot be the final description of nature at the most fundamental level. Additional elementary particles and interactions are an absolute necessity but have so far evaded our experimental efforts. I will highlight the importance of searches for processes that are forbidden within the Standard Model, as these make for clean signatures of new physics. Important examples are searches for lepton flavor violation and baryon number violation, which will be tested to unprecedented levels in upcoming experiments.

51. NT/RIKEN Seminar

"Towards precision event simulation for collider experiments"

Presented by Stefan Hoeche, Fermilab

Friday, January 24, 2020, 2 pm
Building 510, CFNS Seminar Room 2-38

Hosted by: Niklas Mueller

Experimental analyses during the high-luminosity era of the LHC will call for an unprecedented level of precision in event simulation. With the computation of hard cross sections at next-to-leading order accuracy a solved problem, the focus of development has now shifted towards automated precision resummation, i.e. the extension of parton-showers to next-to-leading order accuracy and beyond the leading-color approximation. At the same time, seemingly mundane problems like the consistent matching of four- and five-flavor calculations at next-to-leading order accuracy need to be tackled in order to make precision forecasts for the measurement of b-jet associated processes such as ttbb. I will discuss the theoretical foundations and practical implications of new algorithms that solve these problems and briefly touch on the readiness of event generators for the next generation high-performance computers.

52. RIKEN Lunch Seminar

"NLO impact factor for inclusive photon+dijet production in e+A DIS at small x"

Presented by Kaushik Roy, Stony Brook

Thursday, January 23, 2020, 12 pm
Building 510, Room 2-160

Hosted by: Yuta Kikuchi

We present the first computation of the NLO photon+dijet impact factor in e+A DIS at small x. When combined with the extant results for the JIMWLK small x evolution to NLLx accuracy, this result provides us with a prediction of the photon+dijet cross-section in e+A DIS to O( (\alpha_S)^3 ln(1/x) ) accuracy. The comparison of this result with photon+dijet measurements at a future EIC therefore provides a precision test of the systematics of gluon saturation. In the soft photon limit, one obtains a compact representation of the state-of-the art results for fully inclusive DIS. The novel techniques developed in this computation can also be applied to promote existing LO computations of photon+dijet production in p+A collisions to NLO+NLLx accuracy.

53. HET Seminar

"Precision tests of the Standard Model"

Presented by Robert Szafron, CERN

Wednesday, January 22, 2020, 2:30 pm
Small Seminar Room, Bldg. 510

54. Condensed-Matter Physics & Materials Science Seminar

"Interlayer charge dynamics in metallic transition metal dichalcogenides"

Presented by Edoardo Martino, Ecole Polytechnique Federale de Lausanne (EPFL), Switzerland

Tuesday, January 21, 2020, 11 am
ISB Bldg. 734, Conf. Rm. 201 (upstairs)

Hosted by: Christopher Homes

Layered metallic transition metal dichalcogenides (TMDs) are conventionally seen as two-dimensional conductors, despite a scarcity of systematic studies of the interlayer charge transport. Motivated by the prevailing strategy of functionalizing 2D materials by creating van der Waals heterostructures, we initiated an in-depth study of out-of-plane charge dynamics and emergent properties arising from interlayer coupling. Unprecedented results have been obtained thanks to employing Focused-ion-beam-assisted 3D microfabrication of samples, which enables tailoring geometry and current paths with submicron precision [1]. In this talk, I will present the first transport data revealing c-axis-oriented quasi-one- dimensional electronic states in 1T-TaS2, —a compound with the richest charge density wave phase diagram among TMDs. Temperature dependence of resistivity shows a robust coherent out-of-plane transport, while in-plane conduction is hindered by the presence of a unique nanoarray of charge density wave domains. Consequently, we interpret the highly debated metal-insulator transition in 1T-TaS2 as a Peierls-like instability of the c-axis-oriented orbital chains, in opposition to the long-standing Mott localization picture [2]. Among other highlights of our current research are the anomalous transport properties observed in natural heterostructures or arising from stacking faults. [1] Moll, P. J. (2018). Focused ion beam microstructuring of quantum matter. Annual Review of Condensed Matter Physics, 9, 147-162. [2] Martino, E., Pisoni, A., Ciric, L., Arakcheeva, A., Berger, H., Akrap, A., ... & Forró, L. (2019). Preferential out-of-plane conduction and quasi-one-dimensional electronic states in layered van der Waals material 1T-TaS2. arXiv preprint arXiv:1910.03817.

55. Nuclear Physics Seminar

"Charmonia in Small Systems"

Presented by Krista Smith, Florida State University

Tuesday, January 21, 2020, 11 am
Small Seminar Room, Bldg. 510

Hosted by: Jin Huang

in heavy systems, but has also become an interesting probe in small sys- tems, having been studied by ALICE, ATLAS, CMS, LHCb, PHENIX and STAR. With the recent Nature paper PHENIX published regarding v2 and v3 coe_cients consistent with hydrodynamic ow and the possibil- ity of droplets of QGP present in small system collisions, measurements on the modi_cation of Charmonium in these same small systems have become increasingly relevant. We present the results of J/ measure- ments in the dimuon decay channel for a collection of di_erent systems at the same collision energy. These small systems include: p+p, p+Al, p+Au and 3He+Au at collision energy p SNN = 200 GeV. A comparison of Charmonium modi_cation in 3He+Au and p+Au data was made to look for e_ects of the increased energy present in the _nal state for the 3He+Au case. The results are presented in the form of the observable RAB, the nuclear modi_cation factor, as a function of rapidity, central- ity and transverse momentum, then compared with di_erent theoretical model predictions. Also included in this discussion are future plans to ex- tract the nuclear modi_cation factor for the (2s), the _rst excited state of the J/ meson.

56. HET Seminar

"A Model of neutrino masses and the LHC"

Presented by Seyda Ipek, UC Irvine

Thursday, January 16, 2020, 2:30 pm
Small Seminar Room, Bldg. 510

Hosted by: Peter Denton

Neutrino masses cannot be explained within the Standard Model. Many new physics models address this question by adding right-handed neutrinos to the SM. These right-handed neutrinos are not expected to be observed at the LHC due either to their large masses or small couplings to the SM particles. I will give a different approach, in which we account for the SM neutrino masses via a pesudo-Dirac bino in an R-symmetric SUSY model. I will also give a recast of recent LHC analyses, mainly jets+MET and leptoquark searches, for this model.

57. Condensed-Matter Physics & Materials Science Seminar

"Symmetry Protected Topological Semimetals"

Presented by Jennifer Cano, SUNY-Stony Brook

Thursday, January 16, 2020, 1:30 pm
ISB Bldg. 734, Conf. Rm. 201 (upstairs)

Hosted by: Mark Dean

Topological semimetals can exhibit gapless Fermi arc surface states and unusual transport properties. I will discuss new aspects of the bulk-edge correspondence that elucidate the topological nature of Dirac fermions. I will then present the classification of nodal fermions in both magnetic and non-magnetic space groups. Finally, I will present an outlook for finding material realizations.

58. HET Seminar

"Resolving CP Confusion from Non-Standard Neutrino Interactions"

Presented by Jeff Hyde, Bowdoin

Wednesday, January 15, 2020, 2:30 pm
Small Seminar Room, Bldg. 510

Hosted by: Peter Denton

Non-standard neutrino interactions (NSI) can interfere with measurements of neutrino oscillation parameters at long-baseline experiments, in particular making determination of the CP-violating phase δ ambiguous. Measurements at different baselines or energies may be combined to improve this situation, but it can be difficult to see the influence of individual parameters and determine when degeneracies may exist or be broken. I will show how the relationship between underlying parameters, degeneracies and their breaking may be represented in a convenient way in biprobability space. An application of particular interest is the experimental hints suggesting δ∼−π/2 , which could be consistent with nonzero NSI but the absence of CP violation.

59. CSI Q Seminar

"Postponing the orthogonality catastrophe: efficient state preparation for electronic structure simulations on quantum devices"

Presented by Norman Tubman, NASA Quantum Artificial Intelligence Laboratory

Wednesday, January 15, 2020, 1:30 pm
Training Room, Bldg 725

Hosted by: Layla Hormozi

Despite significant work on resource estimation for quantum simulation of electronic systems, the challenge of preparing states with sufficient ground state support has so far been largely neglected. We investigate this issue in several systems of interest, including organic molecules, transition metal complexes, the uniform electron gas and Hubbard models. Our approach uses a state-of-the-art classical technique for high-fidelity ground state approximation. We find that easy-to-prepare single Slater determinants such as the Hartree-Fock state often have surprisingly robust support on the ground state for many applications of interest. For the most difficult systems, single-determinant reference states may be insufficient, but low-complexity reference states may suffice. For this we introduce a method for preparation of multi-determinant states on quantum computers.

60. Physics Colloquium

"The interface between Arts and Science, a multi-dimensional space"

Presented by Helio Takai, Interim Dean, School of Liberal Arts and Sciences, The Pratt Institute

Tuesday, January 14, 2020, 3:30 pm
Large Seminar Room, Bldg. 510

Hosted by: George Redlinger

The interface between Arts and Science is wide and diverse. Art and Design covers a wide range of activities from Fine Arts to Digital Arts, from Fashion to Industrial Design, and Architecture. In this context, the disciplines of mathematics and sciences have a broad overlap with these creative practices. The science, and technology, from the knowledge of materials to software for virtual and augmented reality, are all foundations to the development of Arts and Design. In all of these areas, one of the main concerns today is the evolution of these practices in a sustainable and ecological manner. Biomaterials, Material Degradation, Software Development, and Robotics, are a few of the subjects relevant to Arts and Design. On the counter flux, Arts can bring new ways to communicate science to a large segment of the population. Art communicates a message through experiences. In this presentation, I will discuss the various interfaces between arts and science, and in particular, those that are relevant to the Pratt Institute.

61. Nuclear Physics Seminar

"Study of nuclear effects in small collision systems connecting proton-proton and heavy-ion collisions"

Presented by Sanghoon Lim, Pusan National University

Tuesday, January 14, 2020, 11 am
Small Seminar Room, Bldg. 510

Hosted by: Jin Huang

The main purpose of relativistic heavy-ion collision experiments is to understand Quark­Gluon Plasma (QGP) which is very hot and dense QCD matters produced in heavy-ion collisions. Early results from RHIC such as jet quenching and elliptic flow are supported for the formation of the QGP. In order to fully understand the properties of the QGP, it is very important to understand initial conditions before the QGP formation. Proton(deuteron)-ion collision is a control experiment to explore this kind of effects from intrinsic nucleus so called cold-nuclear-matter (CNM) effects such as modification of parton · distributions, energy loss, multiple scattering, and break-up of quarkonia states. Another striking results recently observed in small systems are long-range correlations which were believed as one of properties of the QGP. Now, the studies in small systems receives much more attention than that as a control experiment of heavy-ion collisions. I will introduce the interesting results in small collision systems as well as what we can learn from the expected measurements in the future.

62. CSI Q Seminar

"Quantum-Assisted Telescope Arrays"

Presented by Emil Khabiboulline, Harvard University

Monday, January 13, 2020, 3 pm
Training Room, CSI Bldg 725

Hosted by: Andrei Nomerotski

Quantum networks provide a platform for astronomical interferometers capable of imaging faint stellar objects. We present a protocol with efficient use of quantum resources and modest quantum memories. In our approach, the quantum state of incoming photons along with an arrival time index is stored in a binary qubit code at each receiver. Nonlocal retrieval of the quantum state via entanglement-assisted parity checks at the expected photon arrival rate allows for direct extraction of phase difference, effectively circumventing transmission losses between nodes. Compared to prior proposals, our scheme (based on efficient quantum data compression) offers an exponential decrease in required entanglement bandwidth. We show that it can be operated as a broadband interferometer and generalized to multiple sites in the array. We also analyze how imaging based on the quantum Fourier transform provides improved signal-to-noise ratio compared to classical processing. Finally, we discuss physical realizations including photon detection-based quantum state transfer. Experimental implementation is then feasible with near-term technology, enabling optical imaging of astronomical objects akin to well-established radio interferometers and pushing resolution beyond what is practically achievable classically. References: Phys. Rev. Lett. 123, 070504, Phys. Rev. A 100, 022316

63. HET Seminar

"Experimental Probe of Higgs Parity"

Presented by Keisuke Harigaya, IAS

Monday, January 13, 2020, 2:30 pm
Small Seminar Room, Bldg. 510

Hosted by: Peter Denton

Higgs Parity is a spontaneously broken Z2 symmetry exchanging the standard model Higgs with its parity partner. Higgs Parity predicts a dark matter candidate, can solve the strong CP problem, and can be a part of an SO(10) grand unified gauge symmetry. I will show that the Higgs Parity symmetry breaking scale is determined by standard model parameters and predicts experimental signals such as the dark matter detection rate and the proton decay rate. As a result, Higgs Parity provides a tight correlation between future precision measurements of standard model parameters and these experimental signals.

64. HET Lunch Seminar

"Is the muon just a heavy electron?"

Presented by Amarjit Soni, BNL

Friday, January 10, 2020, 12:15 pm
Building 510, Room 2-160

Hosted by: Peter Denton

65. Condensed-Matter Physics & Materials Science Seminar

"Entropic elasticity and negative thermal expansion in crystalline solids"

Presented by Igor Zaliznyak, Brookhaven National Laboratory

Thursday, January 9, 2020, 1:30 pm
ISB Bldg. 734 Conf. Rm. 201

66. HET Seminar

"Precision Physics in the LHC Era"

Presented by Pier Paolo Giardino, BNL

Wednesday, January 8, 2020, 2:30 pm
Small Seminar Room, Bldg. 510

67. Physics Colloquium

"The Proton Remains Puzzling"

Presented by Haiyan Gao, Duke University

Tuesday, January 7, 2020, 3:30 pm
Large Seminar Room, Bldg. 510

Hosted by: Xin Qian

Nucleons (protons and neutrons) are the building blocks of atomic nuclei, and are responsible for more than 99% of the visible matter in the universe. Despite decades of efforts in studying its internal structure, there are still a number of puzzles surrounding the proton such as its spin, mass, and charge radius. The proton charge radius puzzle developed about ten years ago refers to a 5-7 sigma discrepancy between the ultrahigh precise values of the proton charge radius determined from muonic hydrogen Lamb shift measurements and the CODATA values compiled from electron-proton scattering experiments and hydrogen spectroscopy measurements. In this talk I will briefly introduce the proton spin and mass puzzles first. I will then focus on the proton charge radius puzzle, the latest experimental results, and especially the PRad experiment at Jefferson Lab and its result.

68. Chemistry Department Colloquium

"Design of high voltage all-solid-state batteries based on sulfide electrolytes"

Presented by Xin Li, John A. Paulson School of Engineering and Applied Sciences, Harvard University

Tuesday, January 7, 2020, 2 pm
Hamilton Seminar Room, Bldg. 555

Hosted by: Enyuan Hu

Ceramic sulfide solid-electrolytes are amongst the most promising materials for enabling solid-state lithium ion batteries. The ionic conductivities can meet or exceed liquid-electrolytes for such ceramic sulfides, however, there is a theoretical concern about the narrow electrochemical stability window of approximately 1.7-2.1 V vs lithium metal. In addition, ceramic sulfides are frequently plagued by interfacial reactions when combined with common electrode active materials. In this talk, methods for the stabilization of both the bulk electrochemical decompositions and the interfacial reactions will be discussed. Ceramic sulfides are known to substantially swell during electrochemical decay. Such swelling has been shown to provide viable means by which to stabilize electrochemical decomposition in lithium ion batteries. Experimental evidence and theoretical understanding of stability window expansion as the result of mechanical constriction will be discussed. An advanced mechanical constriction technique is applied on all-solid-state batteries constructed with Li10GeP2S12 (LGPS) as the electrolyte and lithium metal as the anode. The decomposition pathway of LGPS at the anode interface is modified by this mechanical constriction and the growth of lithium dendrite is inhibited, leading to excellent rate and cycling performances. On the cathode side, 5V all-solid-state batteries using layered LiCoO2 and spinel as cathodes will be presented and the stabilization mechanisms will be discussed. A combination of electrochemical battery tests, SEM, XAS, XPS and XRD characterizations, and DFT simulations was used. Biosketch Xin Li is an associate professor of materials science at School of Engineering and Applied Sciences (SEAS) at Harvard University, who was an assistant professor at SEAS from 2015 to 2019. Xin Li's research group designs new energy storage materials through advanced characterizations and simulations, with the current focus on solid s

69. Nuclear Physics Seminar

"Physics with heavy ions and exotic hadrons at LHCb"

Presented by Matt Durham, Los Alamos National Lab

Tuesday, January 7, 2020, 11 am
Small Seminar Room, Bldg. 510

Hosted by: Jin Huang

The LHCb Experiment has a growing program dedicated to heavy ion physics. With full tracking, particle ID, and calorimetry capabilities over the forward rapidity interval 2 < y < 5, LHCb covers a unique kinematic range at the LHC. This allows LHCb to fully reconstruct heavy quark states that are sensitive to the very low x structure of nucleons, as well as characterize exotic states that may be composed of more than three valence quarks. This talk will discuss recent results from the LHCb heavy ion program, with a focus on using heavy ion data and techniques to probe the structure of exotic hadrons.

70. NT/RIKEN Seminar

"From Qubits to Quarks: Parton Physics on a Quantum Computer"

Presented by Scott Lawrence

Friday, December 20, 2019, 2 pm
Building 510, CFNS Seminar Room 2-38

Hosted by: Nikhil Karthik

Quantum computers provide a unique way of computing real-time correlators from first principles, a task not yet achievable on classical computers due to the sign problem. The determination of the hadronic tensor on the Euclidean lattice is obstructed by the difficulty of converting Euclidean correlators to real-time correlators. This is a match made in heaven: a lattice field theory simulation on a quantum computer may provide access to PDFs. In this talk we discuss the way in which a quantum computer may naturally solve this problem, outline recent progress on simulating field theories on a quantum computer, and detail the resources needed to perform such a calculation.

71. CSI Q Seminar

"Probing quantum entanglement at the Electron Ion Collider"

Presented by Dmitri Kharzeev, Stony Brook University and BNL

Wednesday, December 18, 2019, 1:30 pm
Training Room, Bldg 725

Hosted by: Layla Hormozi

The structure functions measured in deep-inelastic scattering are related to the entropy of entanglement between the region probed by the virtual photon and the rest of the hadron. This opens new possibilities for experimental and theoretical studies using the Electron Ion Collider. The real-time evolution of the final state in deep-inelastic scattering can be addressed with quantum simulations using the duality between high energy QCD and the Heisenberg spin chain.

72. Physics Colloquium

"3D imaging of nuclei: status towards an EIC"

Presented by Kawtar Hafiti, ANL

Tuesday, December 17, 2019, 3:30 pm
Large Seminar Room, Bldg. 510

Hosted by: Thomas Ullrich

73. NT/RIKEN Seminar

"Helicity-dependent generalization of the JIMWLK evolution and MV model"

Presented by Florian Cougoulic

Friday, December 13, 2019, 2 pm
Building 510, CFNS Seminar Room 2-38

Hosted by: Nikhil Karthik

The small-x evolution equations for the quark and gluon helicity distribution have recently been constructed by finding sub-eikonal corrections to the eikonal shock wave formalism. Those equations are written for correlators of infinite light-cone Wilson lines along with the so-called polarized Wilson lines. Those equations close in the large N_c-limit (N_c is the number of quark colors), but also in the large N_c & N_f-limit (N_f is the number of quark flavors). However, in the shock wave formalism, no closed form can be obtained for arbitrary value of N_c and N_f. For the unpolarized case, the generalization of the Balitsky-Kovchegov equation is done by the Jalilian-Marian—Iancu—McLerran—Weigert—Leonidov—Kovner (JIMWLK) functional evolution equation. Such an approach for the small-x evolution of the helicity is beneficial for numerical evaluation at finite N_c and N_f (beyond previously used limit), and for the evaluation of helicity-dependent operator with an arbitrary number of Wilson lines. We derive an analogue of the JIMWLK evolution equation for the small-x evolution of helicity distributions and obtain an evolution equation for the target weight functional.

74. HET Lunch Discussion

"What to do when there are observers in your theory"

Presented by Robert Garisto, APS

Friday, December 13, 2019, 12:15 pm
Building 510, Room 2-160

Hosted by: Peter Denton

75. CSI Q Seminar

"Integrating ballistic graphene with superconducting resonators - A new building block for detectors and quantum circuits"

Presented by Olli Saira, BNL

Wednesday, December 11, 2019, 1:30 pm
Training Room, Bldg 725

Hosted by: Layla Hormozi

I present measurements of a bolometer device based on boron nitride-encapsulated graphene operating at temperatures of 300 mK and below. Our experiment probes the exquisite properties of graphene that make it an appealing material for detector applications. First, the specific heat of electronic excitations in graphene is low, promising excellent sensitivity as a thermal photodetector. Second, at low temperatures, superconductivity can be induced in a localized region within the flake. This enables the integration of graphene with superconducting microwave circuits routinely used in quantum processors and astronomical detector arrays. Our initial results demonstrate the operating principle of a graphene bolometer with resonator-coupled temperature readout. However, we also observed unexpected heat leakage out of the flake in our first-generation device, which prevented it from reaching its full theoretical performance.

76. C-AD Accelerator Physics Seminar

"High-Intensity Magnetron H- Ion Sources and Injector Development at BNL LINAC"

Presented by Dr. Anatoli Zelenski, BNL

Tuesday, December 10, 2019, 4 pm
BLDG 911B, Large Conference Room

Hosted by: Binping Xiao

77. Condensed-Matter Physics & Materials Science Seminar

"In-situ TEM sample-management solutions Wildfire and Lightning Heating and Biasing – capturing real dynamics in TEM"

Presented by Yevheniy Pivak, DENSsolutions

Monday, December 9, 2019, 11 am
Bldg. 480, Conference Room

Hosted by: Shaobo Cheng

DENSsolutions offers a complete suite of in-situ sample management solutions for unrivalled high resolution imaging in Transmission Electron Microscopes (TEM) under varying environmental conditions including Heating, Biasing, Gases & Liquids. This presentation is aimed at researchers that want to observe their materials in varying real-time dynamic In-situ TEM environments at high resolution. The format of the presentation will include an explanation to the theory behind DENSsolutions' MEMS-based technology, along with brief products introduction. The main topic of the presentation is the Heating and/or Biasing system and its application in the fields of materials science, chemistry and microelectronics. Application examples such as solar cells, ceramics, ReRam, batteries, 2D materials and more will be covered.

78. NT/RIKEN Seminar

"Probing Quark-Gluon Plasma at high resolution"

Presented by Amit Kumar

Friday, December 6, 2019, 2 pm
Building 510, CFNS Seminar Room 2-38

Hosted by: Nikhil Karthik

In the study of the quark-gluon plasma (QGP) in high-energy heavy-ion collisions, jet quenching plays an essential role as hard probes of the properties of the dense strongly interacting matter. In this talk, we present an attempt to probe the underlying structure of the quark-gluon plasma (QGP) at high resolution, based on the extracted jet transport coefficient \hat{q}. We argue that the exchanged momentum k between the hard parton and the medium varies over a range of scales, and for k ≥ 1 GeV, \hat{q} can be expressed in terms of a parton distribution function (PDF). Calculations, based on this reconstructed \hat{q} are compared to data sensitive to the hardcore of jets i.e., the single hadron suppression in terms of the nuclear modification factor R_{AA} and the azimuthal anisotropy parameter v_{2}, as a function of transverse momentum p_{T}, centrality and energy of the collision. It is demonstrated that the scale evolution of the QGP-PDF is responsible for the reduction in the normalization of \hat{q} between fits to Relativistic Heavy-Ion Collider (RHIC) and Large Hadron Collider (LHC) data; a puzzle, first discovered by the JET collaboration.

79. HET Lunch Discussion

"$\pi\pi$ scattering with distillation in lattice QCD"

Presented by Aaron Meyer, Brookhaven National Laboratory

Friday, December 6, 2019, 12:15 pm
Building 510, Room 2-160

80. Particle Physics Seminar

"A New Paradigm for Dark Matter Search at the LHC"

Presented by Yangyang Cheng, Cornell University

Thursday, December 5, 2019, 3 pm
Small Seminar Room, Bldg. 510

Hosted by: Ketevi Assamagan

The existence of dark matter (DM), through astrophysical and cosmological observations, presents some of the most striking evidence of physics beyond the Standard Model. Stringent limits have been placed on DM as a Weakly Interacting Massive Particle (WIMP) from direct and indirection detection as well as collider experiments. If instead of one type of DM particle, nature contains a complex dark sector, the new hidden particles can evade existing DM limits and most direct detection experiments, but may be produced at high-energy colliders like the LHC. Many dark sector models predict long-lived particles with striking collider signature, opening an exciting new paradigm for dark matter search. This talk overviews the landscape for dark matter search, and introduces the physics motivation for a complex dark sector with long-lived particles. It then describes two types of signature-driven dark sector searches at the CMS experiment, for a dark shower and for displaced lepton jets. Finally, the talk discusses prospects for dark sector searches at the High-Luminosity LHC with detector and trigger upgrades, in particular how the new forward detectors and enhanced timing capabilities can reach new phase spaces and sensitivities.

81. CSI Q Seminar

"Quantum supremacy using a programmable superconducting processor"

Presented by Pedram Roushan, Google

Wednesday, December 4, 2019, 1:30 pm
Large Seminar Room, Bldg. 510

Hosted by: Layla Hormozi

The promise of quantum computers is that certain computational tasks might be executed exponentially faster on a quantum processor than on a classical processor1. A fundamental challenge is to build a high-fidelity processor capable of running quantum algorithms in an exponentially large computational space. Here we report the use of a processor with programmable superconducting qubits to create quantum states on 53 qubits, corresponding to a computational state-space of dimension 2^53. Measurements from repeated experiments sample the resulting probability distribution, which we verify using classical simulations. Our Sycamore processor takes about 200 seconds to sample one instance of a quantum circuit a million times—our benchmarks currently indicate that the equivalent task for a state-of-the-art classical supercomputer would take approximately 10,000 years. This dramatic increase in speed compared to all known classical algorithms is an experimental realization of quantum supremacy for this specific computational task, heralding a much-anticipated computing paradigm.

82. Special HET Seminar (Joint BNL/YITP)

"Composite Higgs Models at the LHC and beyond"

Presented by Da Liu, UCDavis

Wednesday, December 4, 2019, 11 am
Small Seminar Room, Bldg. 510

Hosted by: Peter Denton

Compositeness is an elegant way to address the hierarchy problem. In this talk, I will discuss about the phenomenology of the composite Higgs models at the LHC and beyond, in which Higgs arise as Nambu-Goldstone bosons. Under broad assumption of partial compositeness and symmetry breaking pattern, I will discuss about phenomenology of the spin-1 resonances and the top partners and the relevance of their strong interactions in the searches at the LHC. In addition to the direct searches, the LHC has become a precision machine with accumulating enormous data at the High-Luminosity (HL) stage. I will discuss about precision measurement in the di-boson processes and their relevance in the different new physics patterns. Meanwhile, I will talk about the strong multi-pole interaction scenario, in which the transverse SM gauge bosons are also belonging to the strong sector at the multi-TeV scale. This provided a strong motivation for the precision measurement at the LHC. Finally, I will briefly discuss about the universal relationship between the Higgs couplings predicted by the non-linearity and their phenomenological relevance.

83. Special NT/RIKEN Seminar

"Elementary correlation functions in QCD and their application"

Presented by Nicolas Wink, Heidelberg

Wednesday, December 4, 2019, 10 am
Building 510, CFNS Seminar Room 2-38

Hosted by: Nikhil Karthik

The knowledge of all elementary correlation functions in a theory is sufficient to access all possible observables. The computation of these correlation functions in QCD within the Functional Renormalization Group is outlined. For applications, the shear and bulk viscosity in Yang-Mills, as well as diffusive transport for the critical mode in a Low-Energy Effective Theory of QCD are discussed.

84. Physics Colloquium

"The First Stage of the International Linear Collider"

Presented by James Brau, University of Oregon

Tuesday, December 3, 2019, 3:30 pm
Large Seminar Room, Bldg. 510

Hosted by: George Redlinger

The International Linear Collider is now proposed to begin with a first stage at 250 GeV with an initial integrated luminosity goal of 2 ab−1. I will review the plan for the collider and detectors, the key physics expectations, and recent international discussions. The key physics goal of the ILC250 is precision measurements of the Higgs boson couplings. The exceptional precision of model-independent measurements of all major decay modes makes this program sensitive to possible anomalies due to new physics beyond the Standard Model. Other physics goals will be addressed briefly. The ILC250 infrastructure will support an upgrade future of experiments with e+e− collisions at higher energy up to 1 TeV, building on the success of the first 250 GeV stage.

85. Nuclear Physics Seminar

"Initial state fluctuations of QCD conserved charges in heavy-ion collisions"

Presented by Matt Sievert

Tuesday, December 3, 2019, 11 am
Small Seminar Room, Bldg. 510

Hosted by: Alba Soto Ontoso

We initialize the Quantum Chromodynamic conserved charges of baryon number, strangeness, and electric charge arising from gluon splitting into quark-antiquark pairs for the initial conditions of relativistic heavy-ion collisions. A new Monte Carlo procedure that can sample from a generic energy density profile is presented, called Initial Conserved Charges in Nuclear Geometry (ICCING), based on quark and gluon multiplicities derived within the color glass condensate (CGC) effective theory. We find that while baryon number and electric charge have nearly identical geometries to the energy density profile, the initial strangeness distribution is considerable more eccentric and is produced primarily at the hot spots corresponding to temperatures of T > 400 MeV for PbPb collisions at 5.02 TeV.

86. Special Physics Colloquium

"FCC-ee at CERN: High Precision and High Luminosity at the Electroweak Scale"

Presented by Alain Blondel, Guest Professor at CERN

Monday, December 2, 2019, 11 am
Large Seminar Room, Bldg. 510

Hosted by: Maria Chamizo-Llatas / George Redlinger

Abstract: The discovery of the Higgs boson completed the Standard model and particle physics enters a new era, in which new phenomena are required, but at unknown energy scale and coupling strength. This requires a broad program of searches. The broadest program is offered by the Future Circular Collider (FCC) project at CERN, with a ultimate goal of reaching > 100 TeV in pp collisions. The first step of this program is a circular e+e- collider, offering unprecedented levels or precision and sensitivity to feebly coupled particles. Bio: Alain Blondel is Professor emeritus from University of Geneva and guest professor at CERN. He is leading the effort of physics and experiments for the Future Circular Collider FCC-ee at CERN, a high luminosity e+ e- machine able to produce 5x1012 Z, 108 WW events, 2x106 ZH events and more than 106 top quark pairs. The proposals for the FCC were just submitted to the CERN European Strategy for Particle Physics, which hopefully will endorse the FCC 100km facility around CERN providing powerful means to search for answers to the big questions. He previously worked in the T2K experiment, preparing HyperK, towards neutrino CP violation. He has a long career since 1974, with the Gargamelle experiment and LEP as highlights, and was awarded a number of prizes for his creative work, in particular on the determination of the number of neutrinos and the prediction of the top quark mass from radiative corrections.

87. Physics Colloquium

"A High Energy High-Luminosity Electron-Positron Collider using Energy Recovery Linacs"

Presented by Thomas Roser, Brookhaven National Laboratory

Tuesday, November 26, 2019, 3:30 pm
Large Seminar Room, Bldg. 510

Hosted by: Dmitri Denisov / George Redlinger

I will present an alternative approach for a high-energy high-luminosity electron-positron collider. Present designs for high-energy electron-positron colliders are either based on two storage rings with 100 km circumference with a maximum CM energy of 365 GeV or two large linear accelerators with a high energy reach but lower luminosity, especially at the lower initial CM energies. A collider based on storage rings has a high electric power consumption required to compensate for the beam energy losses from the 100 MW of synchrotron radiation power. Using an Energy Recovery Linac (ERL) located in the same-size 100 km tunnel would greatly reduce the beam energy losses while providing higher luminosity in this high-energy collider. Furthermore, this approach could allow for colliding fully polarized electron and positron beams and for extending the CM energy to 600 GeV, which would enable double-Higgs production and the production and measurements of the top Yukawa coupling.

88. NT/RIKEN Seminar

"Critical gravitational collapse and thermalization in small systems"

Presented by Paul Chesler, Harvard University

Friday, November 22, 2019, 2 pm
Building 510, CFNS Seminar Room 2-38

Hosted by: Niklas Karthik

89. HET Lunch Discussion

"Update on the study of critical slowing down in lattice QCD ensemble generation algorithms"

Presented by Chulwoo Jung, Brookhaven National Laboratory

Friday, November 22, 2019, 12:15 pm
Building 510, Room 2-160

Hosted by: Peter Denton

90. Particle Physics Seminar

Presented by Stefano Zambito, Harvard University

Thursday, November 21, 2019, 3 pm
Small Seminar Room, Bldg. 510

Hosted by: Viviana Cavaliere

"After the discovery of the Higgs Boson, the predictions of the Standard Model of particle physics can be extrapolated without inconsistencies all the way up to the Planck mass. Despite this tremendous success, we still remain in the dark about many open puzzles. Why is the weak interaction much stronger than gravity? What is the nature of Dark Matter? Are the strong, weak and electromagnetic forces a lower-energy manifestation of one single fundamental interaction? A possible solution to these questions is provided by Supersymmetry. The key assumption behind many natural supersymmetric models is that the masses of the gluinos, the top squarks and the higgsinos are near the TeV scale, thus within the LHC reach. In this presentation, I will introduce some of the theoretical and phenomenological arguments that motivate the quest for Supersymmetry. I will then outline how I searched for the above-mentioned particles using LHC Run-2 data collected by the ATLAS experiment. Finally, I will focus on my vision of the future and my research plans in high-energy experimental physics."

91. CANCELLED - RIKEN Lunch Seminar

"Shedding light on photon and dilepton spectral functions"

Presented by Greg Jackson, University of Bern

Thursday, November 21, 2019, 12 pm
Building 510, Room 2-160

Hosted by: Yuta Kikuchi

Photons and dileptons offer themselves as 'clean' probes of the quark-gluon plasma because they are unlikely to reinteract once produced. Their emission rates are given via the vector channel spectral function, an object that can ultimately be reconstructed by analytic continuation of lattice data. To confront perturbative results with that data, the NLO corrections are needed in all domains that affect the associated imaginary-time correlator, namely for energies above, below and in the vicinity of the light cone. We summarize recent progress here and, to control an unavoidable snag, we also determine these corrections for the transverse and longitudinal polarizations separately. Our results should help to scrutinize direct spectral reconstruction attempts from lattice QCD.

92. HET Seminar

"Precision Era of the SMEFT: the Higgs and Electroweak Sectors"

Presented by Tyler Corbett, NBI

Wednesday, November 20, 2019, 2:30 pm
Small Seminar Room, Bldg. 510

Hosted by: Peter Denton

I will quickly review the basics of the Standard Model Effective Field Theory (SMEFT) and mention various efforts to build up the foundation of the SMEFT. Next I review the current status of global fits to the open parameters of the SMEFT and motivate the need for precision calculations for the future of the LHC. With this motivation I will elaborate on my recent work on calculations of the Higgs width and the Ward identities in the SMEFT.

93. CSI Q Seminar

"Designing Two-Qubit Gates for Exchange-Only Quantum Computation"

Presented by Nick Bonesteel, Florida State University and NHMFL

Wednesday, November 20, 2019, 1:30 pm
Conference room 201, Bldg 734

Hosted by: Layla Hormozi

In exchange-only quantum computation, qubits are encoded using three or more spin-1/2 particles and quantum gates can be performed by switching on and off, or "pulsing", the isotropic exchange interaction between spins. Finding efficient pulse sequences for realizing two-qubit gates in this way is complicated by the large search space in which they live, and has typically involved numerical brute force search. Here I will give a simple analytic derivation of the most efficient known exchange-pulse sequence for carrying out a controlled-NOT gate, originally found numerically by Fong and Wandzura. I will then show how the ideas behind this derivation can be used to analytically find new pulse sequences for two-qubit gates beyond controlled-NOT.

94. Physics Colloquium

"Towards a quantum internet, and its applications"

Presented by Thomas Jennewein, University of Waterloo

Tuesday, November 19, 2019, 3:30 pm
Large Seminar Room, Bldg. 510

Hosted by: Andrei Nomerotski

Quantum information processing and quantum communication are novel protocols that originate from the very fundamental and philosophical questions on superposition and entanglement raised since the early days of quantum mechanics. Strikingly, these new protocols offer capabilities beyond communication task possible with classical physics. One very important example is the secure key exchange based on the transmission of individual quantum signals between communication partners. The big vision and frontier in the field of quantum communication research is the development of a Quantum Internet, which establishes entanglement between many different users and devices. The basic idea is that similar to today's internet, the Quantum Internet will readily transfer quantum bits, rather than today's classical bits, between users near and far and over multiple different channels and could be used for secure communications, quantum computer networks and metrological applications. I will discuss recent advances on implementations and tools useful for generating and distributing photonic quantum entanglement over robust channels including time-bin encoding and reference-frame-free protocols. I will also present an overview of the upcoming Canadian quantum communication satellite QEYSSAT.

95. Nuclear Physics Seminar

"Polarized Positron Beams at the Electron-Ion Collider - What physics can be done"

Presented by Dr. Eric Voutier, Institut de Physique Nucléaire, CNRS/IN2P3 Université Paris-Sud & Université Paris-Saclay

Tuesday, November 19, 2019, 11 am
Building 510, CFNS Seminar Room 2-38

Hosted by: Salvatore Fazio

96. HET Lunch Discussion

"Higgs and the Lattice"

Presented by Sally Dawson, BNL

Friday, November 15, 2019, 12:15 pm
Building 510, Room 2-160

97. Particle Physics Seminar

"Cosmology: Halo splashback detection"

Presented by Tae-Hyeon Shin, UPenn

Thursday, November 14, 2019, 3 pm
Small Seminar Room, Bldg. 510

Hosted by: Thomas McClintock

98. Particle Physics Seminar

"The NA62 experiment at CERN: recent results and prospects"

Presented by Dr Evgueni Goudzovski

Thursday, November 14, 2019, 1:30 pm
Small Seminar Room, Bldg. 510

Hosted by: Steve Kettell

The NA62 experiment at CERN dedicated to measurements of ultra-rare decays of the charged kaon with the decay-in-flight technique collected a large data set corresponding to 6*10^{12} kaon decays in 2016-2018. The first NA62 results based on parts this data set are presented, including the search for the K+—>pi+nunu decay, as well as searches for lepton number violation and production of heavy neutral leptons in kaon decays. Prospects for these and other measurements are discussed in view of the second NA62 run foreseen in 2021-2024.

99. RIKEN Lunch Seminar

"Revisiting the discovery potential of the isobar run at RHIC"

Presented by Alba Soto Ontoso, BNL

Thursday, November 14, 2019, 12 pm
Building 510, Room 2-160

Hosted by: Yuta Kikuchi

During the spring of 2018, the Relativistic Heavy-Ion Collider carried out an isobar run consisting of Ru+Ru and Zr+Zr collisions at 200 GeV. The main objective of such experimental program was the unambiguous observation of a Chiral Magnetic Effect-driven charge separation. In this talk, I will demonstrate how an experimentally confirmed property of the nuclear structure of Zr, i.e. its neutron skin, significantly reduces the feasibility of such a finding. This study provides a much needed theoretical baseline to meaningfully interpret the recorded experimental data by combining state-of-the art nuclear structure techniques with a dynamical description of heavy-ion collisions in terms of a novel transport model, SMASH.

100. HET Seminar

"Formulating Lattice Field Theory for a Quantum Computer"

Presented by Richard Brower, Boston University

Wednesday, November 13, 2019, 2:30 pm
Small Seminar Room, Bldg. 510

The quantum link (or D-theory) formulation of lattice field theory, introduced 20 years ago by Brower-Chandrasekharan-Wiese, replaced all gauge and matter fields as single bit fermion operators for a Hamiltonian in an extra dimension. This can been recast as real time quantum evolution in Minkowski space ideally suited for Qubit quantum simulations. In addition a map from fermionic (anti-computing operators) to Pauli matrix Qubit has been found using pseudo-fermions and a local Jordan Wigner transformation in the group manifold, which is simpler than the Bravyi-Kitaev map due to local gauge invariance. With the trotter expansions the gauge invariant kernels for U(1) compact QED on triangular lattice are represented as Qubit circuit are ready to be tested on the IMB-Q.

101. CSI Q Seminar

"Quantum Information: History, Development and Applications"

Presented by Vladimir Korepin, Stony Brook University

Wednesday, November 13, 2019, 11 am
Training Room, Bldg 725

Hosted by: Layla Hormozi

History of quantum information will be mentioned. Followed by comments on modern developments. Current projects of the speaker [spin chains and quantum search] will be briefly described.

102. Condensed-Matter Physics & Materials Science Seminar

"Topological transition on anisotropic hexagonal lattices and effective phonon model for the Quantum Hall transition"

Presented by Andreas Sinner, University of Augsburg, Germany

Tuesday, November 12, 2019, 1 pm
ISB Bldg. 734 Conf. Rm. 201 (upstairs)

Hosted by: Alexei Tsvelik

The topology of the band structure, which is determined by the lattice symmetries, has a strong influence on the transport properties. We consider an anisotropic honeycomb lattice and study the effect of a continuously deformed band structure on the conductivity and optical properties. We find a strong suppression of the conductivity in one direction and increment by several orders in another which leand to a considerable change of optical properties. We further study a gap generation in a two-dimensional Dirac fermion system which are coupled to in-plane phonons. At sufficiently strong electron-phonon interaction a gap appears in the spectrum of fermions. The structure of elementary excitations above the gap in the corresponding phase reveals the presence of scale invariant parity breaking terms which resemble Chern-Simons excitations. The Kubo formula remyields quantized Hall plateaux. References: EPL 119, 27001 (2017); PRB 97, 235411 (2018); PRB 93, 125112 (2016); Ann. Phys. 400, 262 (2018); arxiv:1908.00442.

103. HET Lunch Discussion

"Improving Lattice Measurements for B Mesons"

Presented by Peter Boyle (BNL), Brookhaven National Laboratory

Friday, November 8, 2019, 12:15 pm
Building 510, Room 2-160

Hosted by: Peter Denton

104. NSLS-II Friday Lunchtime Seminar

"Underpinning the nuclear fuel cycle with synchrotron and laboratory based X-ray absorption spectroscopy"

Presented by Neil Hyatt, University of Sheffield, United Kingdom

Friday, November 8, 2019, 12 pm
NSLS-II Bldg. 743 Room 156

Hosted by: Ignace Jarrige

Nuclear energy provides about 30% of the world's low carbon electricity supply, from more than 450 civil nuclear reactors. The supporting nuclear fuel cycle comprises a suite of industrial processes, which transform uranium ore into nuclear fuel, and support reactor operations, decommissioning, waste management, and geological disposal. This seminar will highlight three case studies in the application of X-ray absorption spectroscopy (XAS) in the nuclear fuel cycle, embracing environmental contamination, nuclear forensics, and radioactive waste management. In addition to exploitation of state of the art micro-focus multi-modal beamlines at synchrotron light sources, I will also show how we are using new developments in laboratory based XAS instrumentation, to probe element speciation in nuclear materials.

105. CSI Q Seminar

"Many-body physics with atoms and molecules under quantum control"

Presented by Sebastain Will, Columbia University

Thursday, November 7, 2019, 3 pm
Conference room 201, Bldg 734

Hosted by: Layla Hormozi

Over the past decade, quantum simulators based on ultracold atoms have emerged as a powerful tool to address open questions in strongly interacting systems and nonequilibrium quantum dynamics that have relevance in all areas of physics, from strongly correlated materials to cosmology. Today, quantum simulators based on ultracold dipolar molecules are within experimental reach, which exploit long-range dipole-dipole interactions and will give access to new classes of strongly correlated many-body systems. In this talk, I will present our efforts towards quantum simulation with ultracold dipolar molecules. In trailblazing experiments we have demonstrated the creation of ultracold molecules via atom-by-atom assembly, which yields complete control over the molecular degrees of freedom, including electronic, vibrational, rotational, and nuclear spin states. Exploiting this control, we have observed long nuclear spin coherence times in molecular ensembles, which makes ultracold molecules an interesting candidate for the realization of a long-lived quantum memory. In addition, the dipole-dipole interactions between molecules can be flexibly tuned via external electrostatic and microwave fields. This motivates our current work towards two-dimensional systems of strongly interacting molecules, which promises access to novel quantum phases, will enable high-speed simulation of quantum magnetism, and points towards potential quantum computing schemes based on ultracold molecules. In the end, I will briefly present our new project on enhancing quantum coherence by dissipation in programmable atomic arrays. For this effort we will develop a novel nanophotonic platform that will enable trapping of individual atoms in optical tweezer arrays with unprecedented accuracy and high-speed tunability.

106. Particle Physics Seminar

"Latest neutrino cross-section results from MicroBooNE"

Presented by Dr. Kirsty Duffy, FNAL

Thursday, November 7, 2019, 3 pm
Small Seminar Room, Bldg. 510

Hosted by: Xin Qian

MicroBooNE, the Micro Booster Neutrino Experiment at Fermilab, is an 85-ton active mass liquid argon time projection chamber (LArTPC) located in the Booster Neutrino Beam at Fermilab. The LArTPC technology with 3mm wire spacing enables high-precision imaging of neutrino interactions, which leads to high-efficiency, low-threshold measurements with full angular coverage. As the largest liquid argon detector worldwide taking neutrino beam data, MicroBooNE provides a unique opportunity to investigate neutrino interactions in neutrino-argon scattering at O(1 GeV) energies. These measurements are of broad interest to neutrino physicists because of their application to Fermilab Short Baseline Neutrino program and the Deep Underground Neutrino Experiment (which will both rely on LArTPC technology), as well as the possibility for new insights into A-dependent effects in neutrino scattering on heavier targets such as argon. In this seminar I will present the most recent cross-section results from MicroBooNE, including measurements of inclusive charged-current neutrino scattering, neutral pion production, and low-energy protons. Many of the results I will show represent the first measurements of these interactions on argon nuclei, as well as an exciting demonstration of the potential of LArTPC detector technology to improve our current understanding of neutrino scattering physics.

107. Physics Colloquium

"Changing Flavor: the Universe's Weirdest Particle"

Presented by Kirsty Duffy - Leona Woods Award Winner, FNAL

Tuesday, November 5, 2019, 3:30 pm
Large Seminar Room, Bldg. 510

Neutrinos are some of the most abundant–but elusive–constituents of matter in the universe. It has been firmly established that neutrinos can change flavor (or "oscillate"), as recognized by the 2015 Nobel Prize, and in recent years the field has moved beyond the "discovery" phase to focus on precise measurements of the parameters that determine neutrino oscillation. As our understanding improves, it opens doors to new discoveries about the nature of this little-understood particle. This is a very exciting time in neutrino physics there exists a wealth of fascinating questions to investigate, including recent tantalizing hints of large neutrino-sector CP violation, and we are rapidly developing the tools to answer them. As the United States HEP community leads the next generation of neutrino oscillation experiments, I will give an overview of the field: from the initial discovery of the neutrino, to the first evidence for oscillation, to the most recent results from current long-baseline oscillation experiments such as T2K and NOvA. I will finish by discussing the exciting future prospect of the Deep Underground Neutrino Experiment and the liquid argon time projection chamber technology that makes it possible, including recent results and examples from my own work on MicroBooNE, a liquid argon neutrino detector currently taking data at Fermilab

108. HET Lunch Discussion

"Neutrino Windows to New Physics"

Presented by Julia Gehrlein

Friday, November 1, 2019, 12:15 pm
Building 510, Room 2-160

Hosted by: Peter Denton

109. Special NT/RIKEN Seminar

"Relaxation Time for Strange Quark Spin in Rotating Quark-Gluon Plasma"

Presented by Joseph Kapusta

Thursday, October 31, 2019, 2 pm
Building 510, CFNS Room 2-38

Hosted by: Nikhil Karthik

110. CSI Q Seminar

"Characterizing readout in quantum computers: does the reading '0' really mean 0 and '1' really 1?"

Presented by Tzu-Chieh Wei, Stony Brook University

Wednesday, October 30, 2019, 3 pm
Training Room, Bldg 725

Hosted by: Layla Hormozi

Typical quantum computation includes three stages: state initialization, gate operations and readout. There are tomographic tools on quantum state and process tomography, as well as one that is often ignored, i.e. the detector tomography. It is important to characterize the readout in interpreting experiments on quantum computers. We use quantum detector tomography to characterize the qubit readout in terms of measurement POVMs on IBM Quantum Computers (e.g. IBM Q 5 Tenerife and IBM Q 5 Yorktown). Our results suggest that the characterized detector model deviates from the ideal projectors, ranging from 10 to 40 percent. This is mostly dominated by classical errors, evident from the shrinkage of arrows in the corresponding Bloch-vector representations. There are also small deviations that are not classical', of order 3 percent or less, represented by the tilt of the arrows from the z axis. Further improvement on this characterization can be made by adopting two- or more-qubit detector models instead of independent single-qubit detectors for all the qubits in one device. We also find evidence indicating correlations in the detector behavior, i.e. the detector characterization is slightly altered (to a few percent) when other qubits and their detectors are in operation. Such peculiar behavior is consistent with characterization from the more sophisticated approach of the gate set tomography. Finally, we also discuss how the characterized detectors' POVM, despite deviation from the ideal projectors, can be used to estimate the ideal detection distribution.

111. HET Seminar

"Elastic neutrino-electron scattering in effective field theory"

Presented by Oleksandr Tomalak, Kentucky University

Wednesday, October 30, 2019, 2:30 pm
Small Seminar Room, Bldg. 510

Elastic neutrino-electron scattering provides an important tool for normalizing neutrino flux in modern experiments. This process is subject to large radiative corrections. We determine the Fermi effective theory performing the one-loop matching to the Standard model at the electroweak scale with subsequent running down to low energies. Based on this theory, we analytically evaluate virtual corrections and distributions with one radiated photon beyond the electron energy spectrum and provide the resulting scattering cross sections quantifying errors for the first time. We discuss the relevance of radiative corrections depending on conditions of modern accelerator-based neutrino experiments.

112. Physics Colloquium

"New Physics Probes in Future Neutrino Experiments"

Presented by Peter Denton, BNL

Tuesday, October 29, 2019, 3:30 pm
Large Seminar Room, Bldg. 510

Hosted by: Mary Bishai

Neutrino physics is a broad and diverse field, both experimentally and theoretically. As the standard oscillation picture begins to settle we are moving into an era where precise tests of the neutrino picture can be made. In this talk I will discuss the present and future status of many theoretical probes and a broad range of experiments spanning twenty orders of magnitude in neutrino energy. In particular, I will highlight the strongly interconnected nature of new physics studies in the neutrino sector.

113. Computational Science Initiative Event

"Learning Parameters and Constitutive Relationships with Physics-Informed Machine Learning Methods"

Presented by Alexandre Tartakovsky, Computational Mathematics in the Advanced Computing, Mathematics and Data Division Pacific Northwest National Laboratory

Monday, October 28, 2019, 11 am
Bldg. 725 training room

Hosted by: Kerstin Kleese van Dam

114. Chemistry Department Colloquium

"Electronic Cooperativity in Supported Single and Multinuclear-Sites for Catalytic C-C and C-H Bond Functionalization"

Presented by Dr. Massimiliano Delferro, Argonne National Laboratory

Monday, October 28, 2019, 11 am
Hamilton Seminar Room, Bldg. 555

Hosted by: Sanjaya Senanayake

Systematic study of the interactions between organometallic catalysts and metal oxide support materials is essential for the realization of rational design in heterogeneous catalysis. In this talk, I will describe the stoichiometric and catalytic chemistry of a series of organometallic complex chemisorbed on a variety of metal oxides as a multifaceted probe for stereoelectronic communication between the support and organometallic center. Electrophilic bond activation was explored in the context of stoichiometric hydrogenolysis as well as catalytic hydrogenation, dehydrogenation, and H/D exchange. Strongly acidic modified metal oxides such as sulfated zirconia engender high levels of activity toward electrophilic bond activation of both sp2 and sp3 C–H bonds, including the rapid activation of methane at room temperature; however, the global trend for the supports studied here does not suggest a direct correlation between activity and surface Brønsted acidity, and more complex metal surface interactions are at play.

115. NT/RIKEN Seminar

"Detectability of phase transitions from multi-messenger observations"

Presented by Sophia Han, Ohio University

Friday, October 25, 2019, 2 pm
Building 510, CFNS Seminar Room 2-38

Hosted by: Nikhil Karthik

There is as yet no firm evidence for quark matter in neutron stars. This is mainly because of the lack of direct probes of the opaque neutron star interior, and the lack of clear qualitative difference between hadronic and quark phases. The detection of GW170817 has offered a first example of how gravitational waves can be used to constrain the equation of state (EoS) of ultra-dense matter. We shall discuss taking into account currently available information how to reveal possible phase transitions in neutron stars: the steadily growing body of astrophysical data and supported laboratory experiments should eventually allow us to narrow down the options by combining these various observations. We survey the proposed signatures of exotic matter, and emphasize the importance of data from neutron star mergers.

116. HET Lunch Discussion

"LIGO/Virgo Black Holes from a First Order "QCD" Phase Transition"

Presented by Hooman Davoudiasl, Brookhaven National Laboratory

Friday, October 25, 2019, 12:15 pm
Building 510, Room 2-160

117. Condensed-Matter Physics & Materials Science Seminar

"Engineering magnetism with light with the novel photovoltaic perovskite CH3NH3PbI3"

Presented by László Forró, Ecole Polytechnique Fédérale de Lausanne, Switzerland

Thursday, October 24, 2019, 2:30 pm
ISB Bldg. 734 Conf. Rm. 201 (upstairs)

Hosted by: Cedomir Petrovic

The demand for ever-increasing density of information storage and speed of manipulation boosts an intense search for new magnetic materials and novel ways of controlling the magnetic bit. Here, we report the synthesis of a ferromagnetic photovoltaic CH3NH3(Mn:Pb)I3 material in which the photo-excited electrons rapidly melt the local magnetic order through the Ruderman–Kittel–Kasuya–Yosida interactions without heating up the spin system (1). Similar effect was observed in La1-xSrxMnO3/CH3NH3PbI3 heterostructure in which Tc can be tuned by x (2). The observed optical melting of magnetism could be of practical importance, for example, in a magnetic thin film of a hard drive, where a small magnetic writing field could change the magnetic bit. Our method needs only a low-power visible light source, providing isothermal switching, and a small magnetic guide-field to overcompensate the stray field of neighboring bits. Acknowledgment: The work has been performed in collaboration with B. Náfrádi, E. Horváth, A, Arakcheeva, P. Szirmai, M. Spina, H. Lee, O.V. Yazyev, D. Chernyshov, and many others. The research was partially supported by the ERC Advanced Grant (PICOPROP#670918). Reference : 1. Nafradi et al, Nature Communications, 7, 13406, (2016) 2. Nafradi et al, submitted to PNAS

118. CSI Q Seminar

"Universal logical gate sets with constant-depth circuits for topological and hyperbolic quantum codes"

Presented by Guanyu Zhu, IBM T.J. Watson Research Center

Wednesday, October 23, 2019, 3 pm
Conference Room 201, Bldg 734

Hosted by: Layla Hormozi

A fundamental question in the theory of quantum computation is to understand the ultimate space-time resource costs for performing a universal set of logical quantum gates to arbitrary precision. To date, common approaches for implementing a universal logical gate set, such as schemes utilizing magic state distillation, require a substantial space-time overhead. In this work, we show that braids and Dehn twists, which generate the mapping class group of a generic high genus surface and correspond to logical gates on encoded qubits in arbitrary topological codes, can be performed through a constant depth circuit acting on the physical qubits. In particular, the circuit depth is independent of code distance d and system size. The constant depth circuit is composed of a local quantum circuit, which implements a local geometry deformation, and a permutation of qubits. When applied to anyon braiding or Dehn twists in the Fibonacci Turaev-Viro code based on the Levin-Wen model, our results demonstrate that a universal logical gate set can be implemented on encoded qubits in O(1) time through a constant depth unitary quantum circuit, and without increasing the asymptotic scaling of the space overhead. Our results for Dehn twists can be extended to the context of hyperbolic Turaev-Viro codes as well, which have constant space overhead (constant rate encoding). This implies the possibility of achieving a space-time overhead of O(d/log d), which is optimal to date. From a conceptual perspective, our results reveal a deep connection between the geometry of quantum many-body states and the complexity of quantum circuits. References: arXiv:1806.06078,arXiv:1806.02358, Quantum 3, 180 (2019) (arXiv:1901.11029).

119. HET Seminar

"Neutrino Propagation in Matter: 3 flavors & beyond (joint BNL/YITP seminar (at BNL))"

Presented by Stephen Parke, FNAL

Wednesday, October 23, 2019, 2:30 pm
Small Seminar Room, Bldg. 510

The Wolfenstein matter effect significantly alters neutrino flavor transformations in matter. This effect is responsible for the 1/3 reduction in the solar electron neutrino flux observed by Davis and also has significant effects in terrestrial oscillation experiments such as T2K, NOvA, DUNE and T2HK/K. In this seminar I will present some recent results on 3 (& beyond) flavor matter effects for long baseline experiments.

120. Physics Colloquium

"KATRIN and the Neutrino Mass Scale"

Presented by Diana Parno, Carnegie Mellon University

Tuesday, October 22, 2019, 3:30 pm
Large Seminar Room, Bldg. 510

Hosted by: Xin Qian

Ever since it was first hypothesized 89 years ago, the strange and ghostly particle called the neutrino has mystified and inspired particle and nuclear physicists. After decades of experimental and theoretical work, we have now firmly established that neutrinos have mass, and yet their absolute mass scale remains unknown. Now, after many years of painstaking design, construction, and commissioning work, the Karlsruhe Tritium Neutrino experiment (KATRIN) has recently improved the world's best direct neutrino-mass sensitivity by a factor of 2, with more improvements to come. I will give a tour of KATRIN's 70-m beamline, share some of our adventures with engineering challenges and novel backgrounds, describe our spectral fits and systematic uncertainties, and show a glimpse of KATRIN's future.

121. Center for Functional Nanomaterials Seminar

"Heterogeneous Chemistry at Liquid/Vapor Interfaces Investigated with Photoelectron Spectroscopy"

Presented by Hendrik Bluhm, Fritz Haber Institute of the Max Planck Society, Department of Inorganic Chemistry, Faradayweg, Berlin, Germany

Monday, October 21, 2019, 11 am
Bldg.735 (CFN) 1st floor conference room

Hosted by: Ashley Head

Aqueous solution/vapor interfaces govern important phenomena in the environment and atmosphere, including the uptake and release of trace gases by aerosols and CO2 sequestration by the oceans.[1] A detailed understanding of these processes requires the investigation of liquid/vapor interfaces with chemical sensitivity and interface specificity under ambient conditions, i.e., temperatures above 200 K and water vapour pressures in the millibar to tens of millibar pressure range. This talk will discuss opportunities and challenges for investigations of liquid/vapor interfaces using X-ray photoelectron spectroscopy and describe some recent experiments that have focused on the propensity of certain ions and the role of surfactants at the liquid/vapor interface. [1] O. Björneholm et al., Chem. Rev. 116, 7698 (2016).

122. NT/RIKEN Seminar

"The bulk viscosity of QCD in the chiral limit"

Presented by Derek Teaney, Stony Brook

Friday, October 18, 2019, 2 pm
Building 510, CFNS Room 2-38

In the chiral limit, the long distance effective theory of QCD at finite temperature is not hydrodynamics but a kind of non-abelian superfluid hydrodynamics. We describe this theory and its viscous corrections, including also a correction due to the finite quark mass. At finite quark mass, the long distance theory is ordinary hydrodynamics, and the superfluid theory then just determines non-analytic in the quark mass corrections to the transport coefficients of QCD, akin to the "long time tails" of hydro. We show how this works out for the bulk viscosity. In chiral perturbation theory the dissipative parameters of the superfluid theory can be computed diagrammatically, and we do this. These results then determine the leading order the bulk viscosity of the pion gas close to the chiral limit.

123. HET Lunch Discussion

"Quantum Computing Schwinger Model"

Presented by Taku Izubuchi, BNL HET & RIKEN BNL

Friday, October 18, 2019, 12:15 pm
Building 510, Room 2-160

124. RIKEN Lunch Seminar

"Bottomonia in QGP from lattice QCD: Beyond the ground states"

Presented by Rasmus Larsen, BNL

Thursday, October 17, 2019, 12 pm
Building 510, Room 2-160

Hosted by: Yuta Kikuchi

Using novel lattice (non-relativistic) QCD techniques, for the first time, we will present results pertaining to the fate of Υ(1S), Υ(2S) and Υ(3S) in QGP. We will present results on how the masses of these states change with temperature, as well as how their spatial sizes change. Finally, we will also show new lattice QCD results on excited P-wave bottomonia in QGP.

125. HET Seminar

"Next generation kinematic variables for signal discovery and measurement in colliders"

Presented by Prasanth Shyamsundar, Florida

Wednesday, October 16, 2019, 2:30 pm
Small Seminar Room, Bldg. 510

High energy physics data, even at the parton level, is high dimensional. Analyzing the distribution of collider events in the full phase-space comes with several challenges—insufficient computational resources to scan the full phase-space, insufficient data to populate it, difficulty in validating monte carlo in the full phase-space, etc. One way to address the curse of dimensionality is to reduce it. At the parton level, this is typically done by constructing kinematic event variables. But this dimensionality reduction is accompanied by information loss, so it becomes important to construct "good" event variables that capture the main features of the phase-space distribution and minimize information loss. Construction of good event variables is a challenging task for event topologies with missing particles in the final state. In this talk we'll look at a new class of kinematic event "variables" that can produce mass bumps even for event topologies with missing particles. And in the process, we'll introduce a brand new way of visualizing and representing high dimensional data, which can open up a world of possibilities for new data analysis techniques.

126. Physics Colloquium

"Trapped Ion Quantum Computers"

Presented by Boris Blinov, University of Washington

Tuesday, October 15, 2019, 3:30 pm
Large Seminar Room, Bldg. 510

Hosted by: Andrei Nomerotski

System of cold trapped atomic ions has all key features necessary for implementing quantum computation, and many demonstrations of high fidelity quantum logic gates, high fidelity information storage and readout have been made in recent years. However, scalability remains an elusive goal. I will describe one possible avenue to a scalable ion trap quantum computing architecture known as the MUSIQC architecture, in which an expandable number of Elementary Logic Units (ELUs), microfabricated traps holding linear chains of 10 to 100 ions, are linked together using photonic interface to form a modular large-scale system. Local quantum gates are performed using motional coupling between ions in the same trap. One or two ions in each chain are reserved for performing a slower entanglement operation between ions in different ion traps coupled by optical fibers. This long distance entanglement will be accomplished using photon-mediated ion-ion entanglement, in which pairs of ions are projected into an entangled Bell state by a combined measurement of their emitted single photons. It is beneficial to separate the fast motional coupling and the slower remote ion entanglement to different ion species, ytterbium and barium respectively, whose atomic transitions are widely separated in frequency, yet atomic masses are relatively similar. I will comment on the current state of the art of this architecture, and briefly mention our work on two-dimensional trapped ion crystals, and an effort towards linking trapped ion qubits and solid state spins.

127. CSI Q Seminar

"Quantum simulation of quantum field theory on the light front"

Presented by Peter Love, Tufts University and BNL

Tuesday, October 15, 2019, 12 pm
Training Room, Bldg 725

Hosted by: Layla Hormozi

Quantum simulation proposes to use future quantum computers to calculate properties of quantum systems. The simulation of quantum field theories by any means is a challenge, and quantum algorithms for problems in fundamental physics are a natural target for quantum computation. We will show that the light front formulation of quantum field theory is particularly useful in this regard. We analyze a simple theory in 1 + 1D and show how computation of quantities of interest in this theory is analogous to quantum algorithms for chemistry that we understand in detail.

128. Condensed-Matter Physics & Materials Science Seminar

"Heavy-fermion quantum criticality and unconventional superconductivity"

Presented by Frank Stegllich, Max-Planck-Institute for Chemical Physics & Solids, Germany

Tuesday, October 15, 2019, 11 am
ISB Bldg. 734, Conf. Rm. 201 (upstairs)

Hosted by: Cedomir Petrovic

Heavy-fermion (HF) metals, i.e., intermetallic compounds of certain lanthanides and actinides, have been subject of intensive investigations over the last few decades. These research activities have furnished important discoveries, such as of unconventional superconductivity (SC) ("beyond BCS") and unconventional quantum criticality ("beyond Landau"). About fifty HF superconductors are currently known, more than half of which exhibiting a quantum critical point (QCP) where antiferromagnetic (AF) order is smoothly suppressed by tuning a non-thermal control parameter like pressure or magnetic field. Two variants of HF AF-QCPs have yet been established, i.e., a conventional ("3D SDW") and an unconventional, partial Mott ("Kondo destroying") QCP [1, 2]. In clean, stoichiometric HF metals, the huge entropy accumulated at such an AF QCP is commonly removed by forming an unconventional superconducting phase. The apparent validity of this 'quantum critical paradigm' will be illustrated in the first part of the talk by addressing exemplary quantum critical materials, i.e., the isostructural compounds YbRh2Si2 and CeCu2Si2. The former system exhibits a partial-Mott QCP as reflected by, e.g., an abrupt jump of the Fermi-surface volume [3- 5] and a violation of the Wiedemann-Franz law [6, 7]. For this compound, no SC had been detected down to 10 mK, the lowest temperature accessible in a commercial 3He-4He dilution refrigerator [8]. However, recent magnetic and specific-heat measurements performed in a nuclear demagnetization cryostat down to about 1 mK revealed HF, i.e., unconventional, SC below Tc = 2 mK [9]. CeCu2Si2, the first HF superconductor [10], exhibits SC at a 3D SDW-QCP and was considered a (one-band) d-wave superconductor until a few years ago, when its specific heat was found to exhibit two-gap behavior and exponential temperature dependence at very low temperatures [11]. Based on atomic substitution [12],

129. NT/RIKEN Seminar

"JIMWLK equation from quantum-classical correspondence"

Presented by Ming Li, University of Connecticut

Friday, October 11, 2019, 2 pm
Building 510, CFNS Room 2-38

Hosted by: Niklas Mueller

In this talk, I will examine the status of the JIMWLK evolution equation in relation to the effective density matrix of a high energy hadronic system. The high energy evolution of this density matrix which is associated with the Hilbert space completely spanned by color charge density operators has the form of Lindblad equation. The JIMWLK equation is reproduced by mapping this Lindblad type quantum mechanical equation onto the classical phase space of the system using Weyl's correspondence rules.

130. Physics Colloquium

"Toward scalable quantum computing in the quantum optical frequency comb""

Presented by Oliver Pfister

Tuesday, October 8, 2019, 3:30 pm
Large Seminar Room, Bldg. 510

Hosted by: Andrei Nomerotski

The resonant (qu)modes of a single optical cavity form a quite large number of well-defined quantum optical fields. When that cavity contains a nonlinear material, i.e., a multiphoton emitter, it becomes an exotic light source, e.g. an optical parametric oscillator (OPO), which, as we have shown, can be made to emit large numbers of qumodes in multimode-squeezed, multipartite- entangled quantum states. We have also shown that said multipartite entanglement can (easily) be made to be of the cluster-state type, which is a major component of a quantum computer. The other major component of a quantum computer would be quantum fault tolerance which, in a nutshell, requires that either some states or gates include some nonpositivity in their Wigner functions. I will present my group's progress on the parallel fronts of massively scalable Gaussian entanglement and non-Gaussian quantum state tomography and engineering toward quantum error correction.

131. NT/RIKEN Seminar

"Resurgence and Non-Perturbative Physics"

Presented by Gerald Dunne, University of Connecticut

Friday, October 4, 2019, 1 pm
Building 510, CFNS Room 2-38

Hosted by: Niklas Mueller

I will review the basic ideas behind the connections between resurgent asymptotics and physics, and report on current applications to quantum field theory and phase transitions.

132. HET Lunch Discussion

"Unifying background with perturbations in Chaplygin gas cosmology"

Presented by Heba Sami, North-West University

Friday, October 4, 2019, 12:15 pm
Building 510, Room 2-160

133. RIKEN Lunch Seminar

"Chiral charge dynamics in Abelian gauge theories at finite temperature"

Presented by Adrien Florio, École polytechnique fédérale de Lausanne

Thursday, October 3, 2019, 12 pm
Building 510, Room 2-160

Hosted by: Yuta Kikuchi

The chiral anomaly present in the standard model can have important phenomenological consequences, especially in cosmology and heavy-ions physics. In this talk, I will focus on the contribution from the Abelian gauge fields. Despite an absence of topologically distinct sectors, they have a surprisingly rich vacuum dynamics, partly because of the chiral anomaly. I will present results obtained from real-time classical lattice simulations of a U(1) gauge field in the presence of a chiral chemical potential. They account for short distance fluctuations, contrary to effective descriptions such as Magneto-Hydrodynamics (MHD). I will discuss various phenomena, like inverse magnetic cascade, which occur in this system. In particular, in presence of a background magnetic field, the chemical potential exponentially decays. The associated chiral decay rate is related to the diffusion of the Abelian Chern-Simons number in a magnetic background, in the absence of chemical potential. The rate obtained from the simulations is an order of magnitude larger than the one predicted by MHD. If this result is shown to be robust under corrections such as Hard Thermal Loops, it will call for a revision of the implications of fermion number and chiral number non-conservation in Abelian theory at finite temperature.

134. HET Seminar

"Reevaluating Reactor Antineutrino Anomalies with Updated Flux Predictions"

Presented by Jeffrey Berryman, University of Kentucky

Wednesday, October 2, 2019, 1:30 pm
Small Seminar Room, Bldg. 510

As the number of experimental searches for oscillations involving additional, sterile neutrinos has grown, the evidence for (or against) the latter's existence has become more ambiguous. Part of this ambiguity is attributable to the predicted flux of antineutrinos from nuclear reactors: the systematic uncertainties that enter into any such evaluation can muddy the water substantially. In this talk, I discuss how the sterile neutrino hypothesis fares when the global reactor antineutrino dataset is analyzed with respect to three particular flux predictions – the traditional Huber-Mueller fluxes and two new calculations – and consider how current and future electron-neutrino disappearance experiments may affect the situation over the coming decade.

135. NT/RIKEN Seminar

"Observing the deformation of nuclei with relativistic nuclear collisions"

Presented by Giuliano Giacalone, IPhT - Saclay

Friday, September 27, 2019, 2 pm
Building 510, CFNS Seminar Room 2-38

Hosted by: Niklas Mueller

The geometry of overlap between two nuclei interacting at high energy determines many of the observables typically investigated in heavy-ion-collision analyses, such as average transverse momenta () and azimuthal anisotropies of the emitted particle distributions. If the colliding nuclei are non-spherical, e.g., if they present a quadrupole deformation and look like ellipsoids, the geometry of interaction experiences nontrivial fluctuations due to the random orientation of the colliding bodies. I introduce an 'event-shape engineering' procedure that allows one to probe the quadrupole deformation of the colliding ions. The method is straightforward. One selects a batch of high-multiplicity (ultracentral) collisions, and within this batch looks at events that present an abnormally large or small of the produced hadrons. I show that these events correspond to configurations in which the colliding nuclei are overlapping along the longer (shorter) side of the prolate (oblate) ellipsoids. In these events, the interaction region has an elliptical shape, whose eccentricity is closely related to the quadrupole deformation of the considered nuclei. Therefore, for collisions of nuclei that are significantly deformed (e.g. 238U and 129Xe nuclei collided at RHIC and LHC) I predict a strong enhancement of elliptic flow in the tails of the distributions of ultracentral events. If validated by experimental data, this method would provide a robust tool to observe the deformations of nuclear ground states at particle colliders (in particular at RHIC).

136. BROOKHAVEN FORUM 2019

"Particle Physics and Cosmology in the 2020's"

Friday, September 27, 2019, 8 am
Berkner Hall (Bldg. 488) Main Lecture Hall

137. RIKEN Lunch Seminar

"Rapidity correlators at unequal rapidity"

Presented by Andrecia Ramnath, University of Jyvaskyla

Thursday, September 26, 2019, 12 pm
Building 510, Room 2-160

Hosted by: Yuta Kikuchi

Unequal rapidity correlations can be studied within the stochastic Langevin picture of JIMWLK evolution in the Colour Glass Condensate effective field theory. By evolving the classical field in the direct and complex conjugate amplitudes, the Langevin formalism can be used to study two-particle production at large rapidity separations. We show how the evolution between the rapidities of the two produced particles can be expressed as a linear equation, even in the full nonlinear limit. In addition, we show how the Langevin formalism for two-particle correlations reduces to a BFKL picture in the dilute limit and in momentum space, providing an interpretation of BFKL evolution as a stochastic process for colour charges.

138. BROOKHAVEN FORUM 2019

"Particle Physics and Cosmology in the 2020's"

Thursday, September 26, 2019, 8 am
Berkner Hall (Bldg. 488) Main Lecture Hall

139. Brookhaven Forum 2019

"Particle Physics and Cosmology in the 2020's"

Wednesday, September 25, 2019, 8 am
Berkner Hall (Bldg. 488) Main Lecture Hall

140. Chemistry Department Seminar

""Probing the Excited-State Reactivity of Transition-Metal Compounds Using Photophysics""

Presented by Dr. Daniela M. Arias-Rotondo, Department of Chemistry

Monday, September 23, 2019, 10 am
Hamilton Seminar Room, Bldg. 555

Hosted by: Matt Bird

Transition metal compounds are ubiquitous throughout the chemical sciences, their presence broadly impacting fields such as organic synthesis and solar energy conversion. This talk illustrates how spectroscopic techniques can be used to understand the intricacies of reactions involving transition metal compounds towards two different applications. The first part of this presentation will focus on the conservation of spin in chemical reactions. Our group has previously shown that spin must be conserved for energy transfer to occur.1 To further our understanding of the effect of spin on other types of reactions, we have combined Ru(II) polypyridyls and Fe(III) oxo/hydroxo-bridged dimers to study how the spin state of the acceptor affects the rate of electron transfer. Through a combination of time-resolved spectroscopy and electrochemical techniques we have shown that excited spin states may be involved in electron transfer, as was predicted by Bominaar and coworkers in their studies involving metalloproteins.2 The second half of this seminar describes the use of energy transfer to activate traditional organometallic catalysts to unlock novel reactivity patterns. In particular, we studied the use of an Ir(III) photosensitizer in combination with a Ni(II) catalyst in the coupling of aryl halides and carboxylic acids.3 Mechanistic studies showed that energy transfer from the photocatalyst to the nickel species promotes the latter to an excited state that can promote a novel C-O bond formation.

141. NT/RIKEN Seminar - CANCELLED

"The bulk viscosity of QCD in the chiral limit"

Presented by Derek Teaney, Stony Brook

Friday, September 20, 2019, 2 pm
Building 510, CFNS Room 2-38

Hosted by: Niklas Mueller

In the chiral limit, the long distance effective theory of QCD at finite temperature is not hydrodynamics but a kind of non-abelian superfluid hydrodynamics. We describe this theory and its viscous corrections, including also a correction due to the finite quark mass. At finite quark mass, the long distance theory is ordinary hydrodynamics, and the superfluid theory then just determines non-analytic in the quark mass corrections to the transport coefficients of QCD, akin to the "long time tails" of hydro. We show how this works out for the bulk viscosity. In chiral perturbation theory the dissipative parameters of the superfluid theory can be computed diagrammatically, and we do this. These results then determine the leading order the bulk viscosity of the pion gas close to the chiral limit.

142. NSLS-II Friday Lunchtime Seminar

"Non-trivial Spin Textures in Ferromagnetic Hetero-Interfaces"

Presented by Ramesh C Budhani, Department of Physics, Morgan State University, Baltimore, MD

Friday, September 20, 2019, 12:30 pm
NSLS-II Bldg. 743 Room 156

143. HET Lunch Discussion

"Snowmass Discussion"

Presented by Viviana Cavaliere, Brookhaven National Lab

Friday, September 20, 2019, 12:15 pm
Building 510, Room 2-160

144. Special Physics Colloquium

"Mega-linear versus Giant-circular. The next big machine for HEP"

Presented by Franco Bedeschi, INFN

Thursday, September 19, 2019, 3:30 pm
Large Seminar Room, Bldg. 510

Hosted by: Dmitri Denisov

Time is coming for a decision on the next particle accelerator at the energy frontier. As Europe is updating its strategy for particle physics, e+e- colliders are standing out as the preferred choice. The physics case for these future colliders and the comparison between the linear and circular option will be reviewed. The status of these projects and the R&D on the detectors required for these machines will also be discussed.

145. NT/RIKEN Seminar

"The bulk viscosity of QCD in the chiral limit"

Presented by Derek Teaney, Stony Brook

Thursday, September 19, 2019, 2 pm
Building 510, CFNS Seminar Room 2-38

Hosted by: Niklas Mueller

In the chiral limit, the long distance effective theory of QCD at finite temperature is not hydrodynamics but a kind of non-abelian superfluid hydrodynamics. We describe this theory and its viscous corrections, including also a correction due to the finite quark mass. At finite quark mass, the long distance theory is ordinary hydrodynamics, and the superfluid theory then just determines non-analytic in the quark mass corrections to the transport coefficients of QCD, akin to the "long time tails" of hydro. We show how this works out for the bulk viscosity. In chiral perturbation theory the dissipative parameters of the superfluid theory can be computed diagrammatically, and we do this. These results then determine the leading order the bulk viscosity of the pion gas close to the chiral limit.

146. Particle Physics Seminar

"Radar detection of neutrino-induced cascades in ice: experimental evidence and future prospects"

Presented by Steven Prohira, The Ohio State University

Thursday, September 12, 2019, 3 pm
Small Seminar Room, Bldg. 510

Hosted by: Alessandro Tricoli

In order to detect ultra-high energy (UHE) neutrinos (? few PeV), tens to hundreds of cubic kilometers of material must be instrumented, owing to the exceedingly low flux. Radio methods have been suggested as the clear way forward in the UHE regime, owing to very long path lengths for radio waves in ice, meaning that a massive volume can be sparsely instrumented. Among radio techniques, the most recent—and most promising—is the radar detection method. Here, radio waves illuminate a volume, and if an UHE neutrino-induced cascade occurs within the volume, these waves are reflected to a distant receiver. In this seminar, we present the first evidence of detection of such a radar reflection, captured at SLAC in experiment T-576. We then present the science case for radar, and show that it has the best discovery potential for a detector technology in the UHE range.

147. RIKEN Lunch Seminar

"Deeply inelastic scattering structure functions on a hybrid quantum computer"

Presented by Andrey Tarasov, BNL

Thursday, September 12, 2019, 12 pm
Building 510, Room 2-160

Hosted by: Yuta Kikuchi

Computation of DIS structure functions from first principles is an outstanding problem in Quantum Chromodynamics (QCD) as it involves matrix elements of products of electromagnetic currents that are light-like separated in Minkowski spacetime. Since Monte Carlo computations in lattice QCD are only robust in Euclidean spacetime, it is worthwhile to ask whether simulations on a quantum computer can be beneficial. In my talk I will outline a strategy to compute deeply inelastic scattering structure functions on a hybrid quantum computer which is based on representation of the fermion determinant in the QCD effective action as a quantum mechanical "worldline" path integral over fermionic and bosonic degrees of freedom. The proper time evolution of these worldlines can be determined on a quantum computer. While extremely challenging in general, the problem simplifies in the Regge limit of QCD, where the interaction of the worldlines with gauge fields is strongly localized in proper time and the corresponding quantum circuits can be written down. As a first application, we employ the Color Glass Condensate effective theory to construct the quantum algorithm for a simple dipole model of the F2 structure function. We outline further how this computation scales up in complexity and extends in scope to other real-time correlation functions.

148. HET Seminar

"Neutrinos at Dark Matter Experiments, and Vice Versa"

Presented by Nirmal Raj, Triumf Lab

Wednesday, September 11, 2019, 2:30 pm
Small Seminar Room, Bldg. 510

Hosted by: Gopolang Mohlabeng

149. Condensed-Matter Physics & Materials Science Seminar

"Nematic superconductivity in twisted bilayer graphene"

Presented by Laura Classen, University of Minnesota

Tuesday, September 10, 2019, 1 pm
ISB Bldg. 734 Conf. Rm. 201 (upstairs)

Hosted by: Alexei Tsvelik

Tunable insulating and superconducting phases have recently been induced in several twisted graphene-based heterostructures. These correlated phases are ascribed to an exceptional band flattening, which comes along with a very large hexagonal moiré pattern in real space. We study this interplay of orders in a phenomenological model for the moiré superlattice with a focus on superconductivity. Motivated by the presence of van-Hove instabilities, we approach the pairing problem as an interaction-induced instability of the Fermi surface in terms of the unbiased functional renormalization group. We find two pairing instabilities with different symmetries being close in energy and show that a similar situation arises in a model specific for twisted bilayer graphene. In view of recent experimental observations that the threefold lattice rotational symmetry is broken in the superconducting state of hole-doped twisted bilayer graphene, we analyze the corresponding Landau-Ginzburg free energy with two superconducting order parameters. The result is, indeed, a mixed ground state that breaks rotation symmetry and leads to nematic superconductivity. Time-reversal symmetry can simultaneously be broken.

150. Nuclear Physics Seminar

"Longitudinal double spin asymmetry for incluisve jet and dijet production in proton-proton collisions at $\sqrt{s} =$ 510 GeV"

Presented by Zilong Chang, BNL

Tuesday, September 10, 2019, 11 am
Small Seminar Room, Bldg. 510

Hosted by: Rongrong Ma

Jets productions from $pp$ collisions at RHIC kinematics are dominated by quark-gluon and gluon-gluon scattering processes. Both of these longitudinal double spin dependent processes have sizable asymmetries in the pseudorapidity range, $-1 < \eta < 1$. Therefore the longitudinal double-spin asymmetry $A_{LL}$ for jets is an effective channel to explore the gluon polarization in the proton. Early STAR inclusive jet $A_{LL}$ results at $\sqrt{s} =$ 200 GeV provided the first evidence of the non-zero gluon polarization at $x >$ 0.05. In this talk, we will report the first measurement of the midrapidity inclusive jet and dijet $A_{LL}$ at $\sqrt{s} =$ 510 GeV. The inclusive jet $A_{LL}$ measurement provides sensitivity to the gluon helicity distribution down to a Bjorken-$x$ of 0.015, while the dijet measurements, binned in four jet-pair topologies, will allow for tighter constraints on the $x$ dependence. Both results are consistent with previous measurements made at $\sqrt{s} =$ 200 GeV and show excellent agreement with predictions from recent next-to-leading order global analyses. In addition the new techniques designed for this analysis, for example, the underlying event correction to the jet transverse energy and its effect on the jet $A_{LL}$ will be discussed.

151. NT/RIKEN Seminar

"Qubit Regularization of Quantum Field Theories"

Presented by Shailesh Chandrasekharan, Duke University

Friday, September 6, 2019, 2 pm
Building 510, CFNS Seminar Room 2-38

Hosted by: Niklas Mueller

Motivated by the desire to study quantum field theories on a quantum computer, we propose a new type of regularization of quantum field theories where in addition to the usual lattice regularization, quantum field theories are constructed with a finite dimensional Hilbert space per lattice site. This is particularly relevant for studying bosonic field theories using a quantum computer since traditional lattice regularization assumes an infinite dimensional Hilbert space per lattice site and hence difficult to formulate on a quantum computer. Here we show that a two qubit model is sufficient to recover the 3d Wilson-Fisher fixed point and the 4d Gaussian fixed point of the O(3) sigma model. On the other hand in 2d, our qubit model does not seem to have a continuum limit although we have to study large lattices to establish this fact. We discuss modifications of our model that could perhaps yield a continuum limit.

152. HET Lunch Discussion - CANCELLED

"Is the muon just a heavy electron"

Presented by Amarjit Soni, BNL

Friday, September 6, 2019, 12:15 pm
Building 510, Room 2-160

153. CFNS Seminar

"Nuclear femtography as a bridge from protons and neutrons to the core of neutron stars"

Presented by Simonetta Liuti, University of Virginia

Thursday, September 5, 2019, 4 pm
Building 510, CFNS Room 2-38

Hosted by: Abha Rajan

In this talk I will address how the science of Nuclear Femtography, probed by deeply virtual exclusive electron nucleon scattering, has revolutionized our approach to exploring the internal structure of the nucleon. Current and planned experiments at the future EIC could in principle allow us to use all the information from data and phenomenology, on one side, to form tomographic images of the nucleon's quark and gluon distributions and, on the other, to reveal the nucleon's internal structure by measuring mechanical properties such as the quark angular momentum, energy density and pressure distributions. While this information is critical for ultimately understanding the working of the color forces, it also defines a new area of research where the fundamental gravitational properties of protons, neutrons and nuclei can be tested through recent astronomical observations constraining the equation of state of neutron stars.

154. Special Nuclear Theory Seminar

"Confinement and Entanglement in Coupled Quantum Systems"

Presented by Masanori Hanada, Stanford/Kyoto

Thursday, September 5, 2019, 12 pm
Building 510, Room 2-160

Hosted by: Rob Pisarski

155. HET Lunch Discussion

"NSI at DUNE"

Presented by Poonam Mehta

Friday, August 30, 2019, 12:15 pm
Building 510, Room 2-160

156. RIKEN Lunch Seminar

"Quantum Black Hole Entropy from 4d Supersymmetric Cardy formula"

Presented by Masazumi Honda, Cambridge

Thursday, August 29, 2019, 12 pm
Building 510, Room 2-160

Hosted by: Yuta Kikuchi

I will talk about supersymmetric index of 4d N=1 supersymmetric theories on S^1xM_3 which counts supersymmetric states. In the first part, I will discuss a general formula to describe an asymptotic behaviour of the index in the limit of shrinking S^1 which we refer to as 4d (refined) supersymmetric Cardy formula. This part is based on arXiv:1611.00380 with Lorenzo Di Pietro. In the second part, I will apply this formula to black hole physics. I will mainly focus on superconformal index of SU(N) N=4 super Yang-Mills theory which is expected to be dual to type IIB superstring theory on AdS_5 x S^5. We will see that the index in the large-N limit reproduces the Bekenstein-Hawking entropy of rotating charged BPS black hole on the gravity side. Our result for finite N makes a prediction to the black hole entropy with full quantum corrections. The second part is based on arXiv:1901.08091.

157. Condensed-Matter Physics & Materials Science Seminar

"Tailoring the twinning of DyBa2Cu3O7-x thin films with atomic-layer-by-layer molecular beam epitaxy"

Presented by Daniel Putzky, Max Planck Institute for Solid State Research, Germany

Monday, August 26, 2019, 1:30 pm
ISB Bldg. 734, Conf. Rm. 201 (upstairs)

Hosted by: Tony Valla/Ilya Drozdov

In this talk I will present the work on high-quality, epitaxial DyBa2Cu3O7-x (DBCO) thin films grown by molecular beam epitaxy (MBE). In contrast to the previous DBCO growth by MBE using co-deposition technique, we have employed an atomic-layer-by-layer shuttering sequence with in-situ RHEED feedback. Films grown on LSAT (100), NGO (110) and STO (100) have a sharp superconducting transition above 80 K. Scanning-transition electron microscopy (STEM) shows atomically sharp substrate-film interface and the absence of stacking faults, unlike films previously grown by PLD. In the second part of the talk I will focus on the structural investigation using x-ray diffraction (XRD). In-plane scans at the KARA synchrotron confirm the epitaxial relationship to the substrate. In addition the formation of twin domains with the bulk-like orthorhombic crystal structure were observed. By reducing the film thickness the tetragonal to orthorhombic phase transition can be suppressed while the films still remain superconducting.

158. NT/RIKEN Seminar

"Symmetries in quantum field theory and quantum gravity"

Presented by Daniel Harlow, MIT

Friday, August 23, 2019, 1:15 pm
Building 510, CFNS Seminar room 2-38

Hosted by: Niklas Mueller

It has long been suspected that symmetries in quantum gravity are highly constrained. In this talk I will describe joint work with Hirosi Ooguri, where we use the power of the AdS/CFT correspondence to prove three conjectures of this type: that there are no global symmetries, that there must be objects transforming in all representations of any gauge symmetry, and that any gauge group must be compact. Real world implications include the existence of magnetic monopoles and neutrinoless double beta decay, although we so far are unable to give estimates for when these should be seen. An important point, which we dwell on at length, is the proper definition of gauge and global symmetries in quantum field theory.

159. HET Discussion - CANCELLED

"TBD"

Presented by Aaron Meyer, BNL

Friday, August 23, 2019, 12:15 pm
Building 510, Room 2-160

160. Condensed-Matter Physics & Materials Science Seminar

"The 2-spinon contribution to the longitudinal structure factor in the XXZ model"

Presented by Isaac Perez Castillo, Institute of Physics, UNAM and London Mathematical Laboratory

Thursday, August 22, 2019, 1:30 pm
ISB Bldg. 734 Conf. Rm. 201 (upstairs)

Hosted by: Alexei Tsvelik

In this work we derive exactly the two-spinon contribution to the longitudinal dynamical structure factor of the anisotropic Heisenberg spin-1/2 chain in the gapped regime by using quantum group approach. We will briefly discuss some of the mathematical difficulties when confronting form factor formulas given by quantum group approach and how to overcome these obstacles. We end up by contrasting our results with those coming from perturbation theory, while comparison to DMRG and experiments are currently underway.

161. NT/RIKEN

"Effective and temperature-dependent viscosities in a hydrodynamically-expanding QCD plasma"

Presented by Jean-Francois Paquet, Duke University

Friday, August 16, 2019, 2 pm
Building 510, CFNS room 2-38

Hosted by: Niklas Mueller

The shear and bulk viscosities of QCD are understood to have non-trivial temperature dependence. The quark-gluon plasma created at RHIC and the LHC provides a unique probe of this temperature dependence for temperatures ranging from ∼150 ~MeV to ∼400−600 MeV. Values of viscosities commonly quoted for the quark-gluon plasma, e.g. η/s∼0.1−0.2 for the shear viscosity to entropy density ratio, are understood to represent `effective viscosities'', which combine the actual temperature-dependence of the transport coefficient with the complex temperature profile of the quark-gluon plasma. Using 0+1D Bjorken hydrodynamics as starting point, we provide a precise definition of effective viscosity for first-order (Navier-Stokes) hydrodynamics. We examine the role of the equation of state by comparing a QCD fluid with a conformal one. We use this definition of effective viscosity to obtain families of bulk viscosities ζ/s(T) that have different temperature dependence but nevertheless produce matching temperature evolutions in 0+1D hydrodynamics. We further extend the definition of effective viscosity to second-order (Israel-Stewart) Bjorken hydrodynamics. We express the second-order effective viscosity in terms of the initial bulk pressure of the system and its first-order effective viscosity, and quantify the approximate degeneracy of these latter two quantities in Bjorken hydrodynamics. We discuss extensions of this work beyond 0+1D, and review implications for phenomenological studies of heavy ion collisions.

162. HET Lunch Discussion

"The Fermi Constant Revisited"

Presented by William Marciano, BNL

Friday, August 16, 2019, 12:15 pm
Building 510, Room 2-95

163. RIKEN Lunch Seminar

"Mean field approach to the Fisher information matrix in deep neural networks"

Presented by Ryo Karakida, AIST, National Institute of Advanced Industrial Science and Technology

Thursday, August 15, 2019, 12 pm
Building 510, Room 1-224

Hosted by: Akio Tomiya

164. Environmental & Climate Sciences Department Seminar

"Experimental and modeling investigation of the OH-initiated heterogeneous oxidation of semi-solid and aqueous saccharide aerosols"

Presented by Hanyu Fan, Department of Chemistry, West Virginia University

Monday, August 12, 2019, 11 am
Conference Room Bldg 815E

Hosted by: Art Sedlacek and Ernie Lewis

Sugars (primary saccharides, saccharide polyols and anhydro-saccharides) are a major class of water-soluble organic carbon (WSOC) that significantly contribute to atmospheric organic aerosol particular matter (PM). [1] The heterogeneous oxidation of organic materials plays a significant role during the chemical aging of organic aerosols in the atmosphere. The kinetic of such heterogeneous reactions has been shown to be very dependent on the chemical component of the particle phase. [2] The experiments were performed using an atmospheric pressure aerosol flow tube coupled with Scanning Mobility Particle Sizer (SMPS), Gas Chromatography – Flame Ionization Detector (GC-FID) and Aerosol Mass Spectrometer or Teflon filter collection. The kinetics are determined from the loss of particle species as a function of OH exposure. We reported results on the OH-initiated heterogeneous oxidation of pure monosaccharide semi solid nanoparticles over a wide range of relative humidity (RH) conditions. The decay rate of the monosaccharide is found to strongly depend on the gas phase water concentration. [3] We recently report results on heterogeneous oxidation of OH radicals with ternary component of monosaccharide-disaccharide-water semi solid nanoparticles over a range of mole ratio of mixtures of monosaccharide and disaccharide. The presence of disaccharide slows down the decay rate of monosaccharide in semi solid phase. [4] Then we moved on to aqueous phase oxidation of saccharides by OH radicals study. Contrast to what we observed in semi solid phase study, the presence of monosaccharide slows down the kinetic of disaccharide in aqueous phase. [5] A reaction-diffusion kinetic model solved in Matlab software is developed in order to investigate the effect composition-dependent diffusion on heterogeneous reaction behaviors in solid phase study. [3,4] Molecular dynamics simulations and kinetic mechanism of the heterogeneous oxidation of aqueous droplets based

165. C-AD Accelerator Physics Seminar

"Storage Rings as Quantum Computers"

Presented by Kevin Brown, BNL

Friday, August 9, 2019, 4 pm
Bldg. 911B, Second Floor, Large Conf. Rm., Rm. A2

There are multiple ways that quantum computer elements have been realized and have been proposed to be realized. These include ion traps, Josephson junctions, Nuclear Magnetic Resonance spin states and optical systems. In this presentation, I will present a new idea; using a storage ring as a quantum computer. The key to building a storage ring quantum computer is to create an ultracold beam in the form of an "ion Coulomb crystal". In a classical Coulomb crystal, a chain of ions is bound into a lattice structure in which the ions remain locked in sequence despite the mutual Coulomb repulsion force between the positively charged ions. In an ion Coulomb crystal, the thermal vibrations of the ions are cooled to extremely low temperature, so that the quantum states in the motion of the ions are observable. There are a number of challenges in realizing such a system, although much can be learned from ion trap systems, since the storage ring is essentially an unbounded ion trap where the ion chains have a finite velocity.

166. Nuclear Theory / RIKEN Seminar

"DIS on a Quantum Extremal RN-AdS Black Hole: with Application to DIS on a Nucleus"

Presented by Kiminad Mamo, Stony Brook University

Thursday, August 8, 2019, 12 pm
Building 510, Room 2-160

Hosted by: Yuta Kikuchi

We consider deep inelastic scattering (DIS) on a dense nucleus described as an extremal RN-AdS black hole with holographic quantum fermions in the bulk. We find that the R-ratio (the ratio of the structure function of the black hole to proton) exhibit shadowing for x < 0.1, anti-shadowing for 0.1 < x < 0.3, EMC-like effect for 0.3 < x < 0.8 and Fermi motion for x > 0.8 in a qualitative agreement with the experimental observation of the ratio for DIS on nucleus for all range of x. We also take the dilute limit of the black hole and show that its R-ratio exhibits EMC-like effect for 0.2 < x < 0.8 and the Fermi motion for x > 0.8, and no shadowing is observed in the dilute limit.

167. Center for Functional Nanomaterials Seminar

"Precursors that live surprisingly long and prosper even at "real catalytic" high temperatures"

Presented by Heriberto Fabio Busnengo

Tuesday, August 6, 2019, 11 am
CFN, Building 735 - first floor conf. rm.

Hosted by: Dario Stacchiola

The dynamics of intrinsic precursors and their role on surface chemistry are presented using quasi-classical trajectory calculations based on force fields parametrized from Density Functional Theory results. Carbon monoxide and methane are used as benchmark molecules, exemplifying non-reactive and reactive sticking processes on Cu(110) and Ir(111) respectively. The role of entropic effects in the stabilization of the precursor state for CO/Cu(110) is presented, as well as an analysis of the extent low energy CH4 molecules thermalize on a hot surface. The theoretical studies are motivated by recent molecular beam experimental findings for both molecules, where the long lifetime of vibrationally excited states on shallow potential wells enable these precursors to "prosper" even at high "real catalytic" temperatures.

168. NT/RIKEN Seminar

"Perturbation Theory of Non-Perturbative QCD"

Presented by Fabio Siringo, University of Catania

Friday, August 2, 2019, 2 pm
Building 510, CFNS Seminar Room 2-38

Hosted by: Niklas Mueller

A purely analytical approach to non-perturbative QCD is discussed. The exact, gauge-fixed, Faddeev-Popov Lagrangian of Yang-Mills theory is studied by the screened massive expansion which emerges from a mere change of the expansion point of ordinary perturbation theory. The gluon propagator has gauge-invariant complex conjugated poles which might give a direct dynamical proof of gluon confinement. Their genuine nature is discussed. Because of BRST symmetry, the analytic properties and the poles are shown to play a central role in the optimization of the expansion, which becomes a very predictive and ab initio tool. While in excellent agreement with the lattice data in the Euclidean space, the expansion provides valuable information in sectors which are not easily explored on the lattice, like Minkowski space and a generic covariant gauge. Moreover, even in the Euclidean space, the method gives a lattice-independent estimate of the running coupling in the continuum limit.

169. HET Lunch Seminar

"Nucleon-Pion States for the Nucleon Form Factors from the Lattice QCD"

Presented by Yong-Chull Jang

Friday, August 2, 2019, 12:15 pm
Building 510, Room 2-160

Hosted by: Peter Denton

170. Physics Colloquium

"Belle II and SuperKEKB: New Physics and the Next Generation"

Presented by Tom Browder, University of Hawai'i at Manoa

Tuesday, July 30, 2019, 3:30 pm
Large Seminar Room, Bldg. 510

Hosted by: David Jaffe

Recent results now suggest that flavor physics could be an alternative path to breaking the Standard Model of particle physics. I will review the startup of Belle II and SuperKEKB, including news from the first physics run that took place April-June 2019 as well as the the long term physics program of Belle II and the innovative technologies that have made it possible. Belle II will soon become the leading experiment for exploration of the physics of B mesons, D mesons and tau leptons. I will also discuss the special role of BNL in Belle II.

171. Nuclear Physics Seminar

"Understanding the nature of heavy-ion collisions in small systems"

Presented by Jacquelyn Noronha-Hostler, Rutgers University

Tuesday, July 30, 2019, 11 am
Small Seminar Room, Bldg. 510

Hosted by: Jiangyong Jia

In recent years our understanding on the limits of the smallest possible droplet of the Quark-Gluon Plasma has been called into question. Experimental results from both the Large Hadron Collider and the Relativistic Heavy Ion Collider have provided hints that the Quark-Gluon Plasma may be produced in systems as small as those formed in pPb or dAu collisions. Yet, alternative explanations still exist from correlations arising from quarks and gluons in a color glass condensate picture. In order to better resolve the distinctions between these two scenarios, I will discuss the possibility of a future system size scan involving ArAr and OO collisions at the Large Hadron collider and make predictions for flow harmonics in both the light and heavy flavor sectors. Additionally, I will discuss the potential of using small deformed ions to help disentangle the color glass condensate scenario versus hydrodynamics where most of these results can be confirmed or denied using experimental data that is already on tape.

172. Condensed-Matter Physics & Materials Science Seminar

"Fermi arcs, nodal and antinodal gaps in cuprates : the 'pairon' model to the rescue"

Presented by William Sacks, Sorbonne University, France

Friday, July 26, 2019, 1:30 pm
ISB Bldg. 734 Conf. Rm. 201 (upstairs)

Hosted by: Ivan Bozovic

Angle-resolved photoemission, in addition to tunneling, has provided key information on the cuprate pairing on the microscopic scale. In particular, in the underdoped regime, the angular dependence of the gap function Δ(θ) deviates from a pure d-wave form such that the antinodal gap value ΔAN and the nodal gap value ΔN completely diverge. On another front, ARPES has firmly established that the enigmatic Fermi arcs, i.e. normal electron excitations around the nodes, exist even below Tc. In this work, we will interpret these experiments based on the 'pairon' model [1] in which the fundamental object is a hole pair bound by its local antiferromagnetic environment on the scale of the coherence length ξAF. The pairon model agrees quantitatively with both the gap function Δ(θ) and the Fermi arcs seen at finite temperature.

173. Physics Department Summer Lectures

"From Raw Data to Physics Results"

Presented by Paul Laycock

Friday, July 26, 2019, 12:30 pm
Small Seminar Room, Bldg. 510

Hosted by: Mary Bishai

Modern nuclear and particle physics experiments generate huge amounts of data that need to be calibrated, processed and analysed so that we can extract and publish physics results. In this talk I will describe the journey of data, from the bits that leave the detectors through its transformation into well-understood physics objects that are analysed by physicists all over the world. We will look in particular at how this exabyte scale problem requires computing and software solutions that operate on a global scale, and take a look at the challenges that still lie ahead of us.

174. HET Lunch Discussion

"Revisiting the Dark Photon Interpretation of the Muon Anomalous Magnetic Moment"

Presented by Gopi Mohlabeng, BNL

Friday, July 26, 2019, 12:15 pm
Building 510, Room 2-160

A massive U(1)′ gauge boson known as a "dark photon" or A′, has long been proposed as a potential explanation for the discrepancy observed between the experimental measurement and theoretical determination of the anomalous magnetic moment of the muon (gμ − 2) anomaly. Recently, experimental results have excluded this possibility for a dark photon exhibiting exclusively visible or invisible decays. In this work, we revisit this idea and consider a model where A′ couples inelastically to dark matter and an excited dark sector state, leading to a more exotic decay topology we refer to as a semi-visible decay. We show that for large mass splittings between the dark sector states this decay mode is enhanced, weakening the previous invisibly decaying dark photon bounds. As a consequence, A′ resolves the gμ− 2 anomaly in a region of parameter space the thermal dark matter component of the Universe is readily explained. Interestingly, it is possible that the semi-visible events we discuss may have been vetoed by experiments searching for invisible dark photon decays. A re-analysis of the data and future searches may be crucial in uncovering this exotic decay mode or closing the window on the dark photon explanation of the gμ− 2 anomaly.

175. HET Lunch Discussions

"Unearthing Kinematic Information in WH Production"

Presented by Sam Homiller, SBU

Friday, July 26, 2019, 12:15 pm
Building 510, Room 2-160

The associated production of a Higgs and a W boson is an important channel not only for observing the Higgs decay to b quark pairs, but also for examining the interactions of the Higgs and gauge fields. Using the inference toolkit MadMiner, which combines matrix element information and machine learning techniques, we examine the sensitivity of this production mode to non-Standard Model (SM) interactions arising in the context of the SM Effective Field Theory. These modern inference techniques maximize the sensitivity to new physics effects by exploiting all the kinematic information in the process and also help us understand how this information is distributed in phase space. In particular, this lets us rigorously evaluate the sensitivity of traditional approaches using histograms of a small number of observables. Based on our study we propose improvements to the recently implemented "Simplified Template Cross Section" templates for the Higgstrahlung process in order to increase the experimental sensitivity of beyond the SM physics at the LHC.

176. Sambamurti Lecture

"Finger-printing a nuclear reactor with neutrinos"

Presented by Thomas Langford, Yale University

Thursday, July 25, 2019, 3:30 pm
Large Seminar Room, Bldg. 510

Hosted by: John Haggerty

Neutrinos have been the most consistently surprising particle of the last few decades. The onset of high-precision experiments has lead to the discovery of neutrino oscillations, possible evidence for beyond the Standard Model sterile neutrinos, and the beginnings of neutrino-based geophysics. Recent measurements of antineutrinos from nuclear reactors have observed flux and spectral discrepancies compared to leading theoretical models. Experiments like Daya Bay and PROSPECT are able to observe the small differences of neutrino emission from different mixtures of nuclear fuel, which may illuminate the origin of this disagreement. These neutrino finger-prints can also be used to investigate the mixture of fuel inside an operating reactor, rekindling interest in neutrino-based reactor monitoring. I will present recent advances which have demonstrated how small-scale experiments utilizing new technologies can advance both fundamental and applied science.

177. RIKEN Lunch Seminar

"Deciphering the z_g distribution in ultrarelativistic heavy ion collisions"

Presented by Paul Caucal, Saclay

Thursday, July 25, 2019, 12 pm
Building 510, Room 2-160

Hosted by: Yuta Kikuchi

178. Nuclear Physics Seminar

"Understanding the nature of heavy-ion collisions in small systems"

Presented by Jacquelyn Noronha-Hostler, Rutgers University

Thursday, July 25, 2019, 11 am
Small Seminar Room, Bldg. 510

Hosted by: Jia Jiangyong

In recent years our understanding on the limits of the smallest possible droplet of the Quark-Gluon Plasma has been called into question. Experimental results from both the Large Hadron Collider and the Relativistic Heavy Ion Collider have provided hints that the Quark-Gluon Plasma may be produced in systems as small as those formed in pPb or dAu collisions. Yet, alternative explanations still exist from correlations arising from quarks and gluons in a color glass condensate picture. In order to better resolve the distinctions between these two scenarios, I will discuss the possibility of a future system size scan involving ArAr and OO collisions at the Large Hadron collider and make predictions for flow harmonics in both the light and heavy flavor sectors. Additionally, I will discuss the potential of using small deformed ions to help disentangle the color glass condensate scenario versus hydrodynamics where most of these results can be confirmed or denied using experimental data that is already on tape.

179. Condensed-Matter Physics & Materials Science Seminar

"Strange superconductivity near an antiferromagnetic heavy-fermion quantum critical point"

Presented by Chung-Hou Chung, Department of Electrophysics, National Chiao-Tung University, Taiwan

Wednesday, July 24, 2019, 1:30 pm
ISB Bldg. 734 Conf. Rm. 201

Hosted by: Alexei Tsvelik

The heavy fermion systems CeMIn5 with M = Co, Rh, Ir, the "115" family, provide a prototypical example of an exotic "strange superconductivity" where unconventional d-wave Cooper pairs get condensed out of an incoherent strange metal normal state, displaying non-Fermi liquid behavior such as: T-linear-resistivity, T-logarithmic specific heat coefficient and a T-power-law singularity in magnetic susceptibility, near an antiferromagnetic quantum critical point [1]. The microscopic origin of strange superconductivity and its link to antiferromagnetic quantum criticality of the strange metal state are still long-standing open issues. We propose a microscopic mechanism for strange superconductors, based on the coexistence and competition between the Kondo correlation and the quasi-2d short-ranged antiferromagnetic resonating-valence-bond (RVB)spin-liquid near the antiferromagnetic quantum critical point via a large-N (Sp(N)) Kondo-Heisenberg model and renormalization group analysis beyond the mean-field level [2]. In the absence of superconductivity, this effective field theory [3] can describe various aspects of strange metal state observed in Ge-substituted YbRh2Si2 [4] close to the field-tuned Kondo breakdown quantum critical point. The interplay of these two effects between the Kondo and RVB physics provides a qualitative understanding on how superconductivity emerges from the strange metal state and the observed superconducting phase diagrams for CeMIn5 [1,2]. References: [1] C. Petrovic et al. J. Phys. Condens. Matt. 13, L337 (2001); S. Zaum et al. Phys. Rev. Lett. 106, 087003 (2011). [2] Y. Y. Chang, F. Hsu, S. Kirchner, C. Y. Mou, T. K. Lee, and C. H. Chung, Phys. Rev. B 99, 094513 (2019). [3] Y. Y. Chang, S. Paschen, and C. H. Chung, Phys. Rev. B 97, 035156 (2018). [4] J. Custers et al, Nature (London) 424, 524 (2003); J. Custers et al. Phys. Rev. Lett. 104, 186402 (2010).

180. Physics Department Summer Lectures

"Searching for and understanding the quark-gluon plasma in heavy-ion"

Presented by Rongrong Ma, BNL

Tuesday, July 23, 2019, 12:30 pm
Small Seminar Room, Bldg. 510

Hosted by: Mary Bishai

Lattice-QCD predicts the occurrence of a phase transition above a critical temperature from ordinary nuclear matter to a new state of matter, usually referred to as the quark-gluon plasma (QGP), in which partons are relevant degrees of freedom. One primary goal of the heavy-ion physics is to create and study the properties of the QGP created in these collisions. The last couple of decades have seen tremendous progresses in understanding the QGP, thanks to the successful operation of dedicated experiments at the RHIC and the LHC. In this lecture, I will discuss the detectors designed for heavy-ion physics, and how an experimentalist turns electronic signal into physics results. Future direction of heavy-ion experiments will also be discussed.

181. Condensed-Matter Physics & Materials Science Seminar

"Electron beam effects on organic ices"

Presented by Marco Beleggia, Technical University of Denmark, Denmark

Monday, July 22, 2019, 11 am
ISB Bldg. 734 Conf. Rm. 201 (upstairs)

Hosted by: Yimei Zhu

While beam damage is often considered detrimental to our quantitative imaging capabilities, the energy and charge injected into the sample as a result of inelastic scattering can be exploited beneficially. This is especially true in radiation-chemistry-type experimental setups in the electron microscope where the beam promotes local wanted chemical reactions. We have observed that by exposing to the electron beam a layer of small volatile organic molecules condensed over a cold substrate results in the formation of a solid product. Evidence suggests that the exposure mechanism driving the formation of a solid product is partial dehydrogenation of the molecules, removal of H2, and progressive increase of the average molecular weight. Contrary to focused electron beam induced deposition, that relies on surface absorption followed by aggregation of mobile species, at cryogenic temperature organic ice molecules are largely immobilized, and act as targets for the incoming electrons throughout the entire thickness of the layer. Therefore, the exposure occurs throughout the volume of the frozen precursor, and the features are essentially determined by the electron distribution, with diffusion/transport parameters bearing little or no relevance. Since larger molecules are less volatile, if the molecular weight increases sufficiently, upon raising the temperature the unexposed areas leave the sample, while the exposed molecules assemble into a solid product in the form of hydrogenated amorphous carbon.

182. Physics Department Summer Lectures

"Introduction to Statistics in High-Energy Physics"

Presented by Xin Qian

Friday, July 19, 2019, 12:30 pm
Small Seminar Room, Bldg. 510

Hosted by: Mary Bishai

In this lecture, I will introduce some basic statistical concepts commonly used in the data analysis of high-energy physics experiments. I will review the basic procedure in setting confidence intervals. Some advanced topics in data unfolding, selection of test statistics, and usage of linear algebra in reducing computation will be touched upon.

183. HET Lunch Seminar

"Probing Dark Matter Particle Properties with Ultra-High-Resolution CMB Lensing"

Presented by Neelima Sehgal, SBU

Friday, July 19, 2019, 12:15 pm
Building 510, Room 2-160

Hosted by: Hooman Davoudiasl

184. Particle Physics Seminar

"Precision Jet Substructure with the ATLAS Detector"

Presented by Jennifer Roloff, BNL

Thursday, July 18, 2019, 3 pm
Small Seminar Room, Bldg. 510

Hosted by: Alessandro Tricoli

185. Physics Department Summer Lecture Series

"Quantum Chromodynamics (QCD) as a many-body theory: An existential tale in four acts"

Presented by Raju Venugopalan, BNL

Tuesday, July 16, 2019, 12:30 pm
Small Seminar Room, Bldg. 510

Hosted by: Mary Bishai

QCD, our nearly perfect theory of the strong interaction, is also deeply profound because all phenomena are emergent features of the many-body dynamics of the quark and gluon fields and the vacuum of the theory. This talk on many-body QCD is organized as a play in four acts: i) Origins, mysteries, symmetries ii) The power and the glory of QCD iii) Surprises from boiling the QCD vacuum in heavy-ion collisions: a) why the world's hottest fluid, albeit also being its most viscous, flows with almost no resistance b) a possible unexpected universality between the hottest and coldest fluids on earth c) What magnetar strength magnetic fields created in heavy-ion collisions may reveal about the topology of the QCD vacuum iv) Looking ahead to the Electron-Ion Collider: what the ultimate IMAX experience may reveal of QCD's mysteries

186. Chemistry Department Seminar

"Nanoparticle Beam Deposition: A Novel Route to the Solvent-Free"

Presented by Richard E. Palmer, Nanomaterials Lab, Swansea University, UK, United Kingdom

Tuesday, July 16, 2019, 11 am
Room 300, 3rd Floor, Chemistry Building 555

Hosted by: Michael White

Size-selected nanoparticles (atomic clusters), deposited onto supports from the beam in the absence of solvents, represent a new class of model systems for catalysis research and possibly small-scale manufacturing of selective catalysts. To translate these novel and well-controlled systems into practical use, two major challenges have to be addressed. (1) Very rarely have the actual structures of clusters been obtained from direct experimental measurements, so the metrology of these new material systems have to improve. The availability of aberration-corrected HAADF STEM is transforming our approach to this structure challenge [1,2]. I will address the atomic structures of size-selected Au clusters, deposited onto standard carbon TEM supports from a mass-selected cluster beam source. Specific examples considered are the "magic number clusters" Au20, Au55, Au309, Au561, and Au923. The results expose, for example, the metastability of frequently observed structures, the nature of equilibrium amongst competing isomers, and the cluster surface and core melting points as a function of size. The cluster beam approach is applicable to more complex nanoparticles too, such as oxides and sulphides [3]. (2) A second major challenge is scale-up, needed to enable the beautiful physics and chemistry of clusters to be exploited in applications, notably catalysis [4]. Compared with the (powerful) colloidal route, the nanocluster beam approach [5] involves no solvents and no ligands, while particles can be size selected by a mass filter, and alloys with challenging combinations of metals can readily be produced. However, the cluster approach has been held back by extremely low rates of particle production, only 1 microgram per hour, sufficient for surface science studies but well below what is desirable even for research-level realistic reaction studies. In an effort to address this scale-up challenge, I will discuss the development of a new kind of nanop

187. NT/RIKEN Seminar

"Topological Superconducting Qubits"

Presented by Javad Shabani, Center for Quantum Phenomena NYU

Friday, July 12, 2019, 2 pm
Building 510, CFNS Room 2-38

Hosted by: Niklas Mueller

Topological superconductivity hosts exotic quasi-particle excitations including Majorana bound states which hold promise for fault-tolerant quantum computing. The theory predicts emergence of Majorana bound states is accompanied by a topological phase transition. We show experimentally in epitaxial Al/InAs Josephson junctions a transition between trivial and topological superconductivity. We observe a minimum of the critical current at the topological transition, indicating a closing and reopening of the superconducting gap induced in InAs, with increasing magnetic field. By embedding the Josephson junction in a phase-sensitive loop geometry, we measure a π-jump in the superconducting phase across the junction when the system is driven through the topological transition. We present a scalable topological qubit architecture to study coherence for computing applications. Funded by DARPA TEE program.

188. Physics Department Summer Lecture Series

"A golden age in physics, an overview of what the...is going on in the RHIC tunnel"

Presented by Rob Pisarski, BNL

Friday, July 12, 2019, 12:30 pm
Small Seminar Room, Bldg. 510

Hosted by: Mary Bishai

I will give a general introduction to the modern theory of "strong" interactions, which involve quarks and gluons. At about a trillion degrees, these form a Quark-Gluon Plasma, which we believe is created in the collisions of heavy ions at very high energies, such as at the Relativistic Heavy Ion Collider here at Brookhaven. I also make extensive comments about the sociology of the field, especially the phenomenon of "As everyone who is anyone knows..."

189. Particle Physics Seminar

"Low-nu Flux Measurement Using Neutrino/Antineutrino-Hydrogen Interactions for Long-baseline Neutrino Oscillation Experiments"

Presented by Hongyue Duyang, University of South Carolina

Thursday, July 11, 2019, 3 pm
Small Seminar Room, Bldg. 510

Hosted by: Chao Zhang

The next generation long-baseline neutrino oscillation experiments such as DUNE (Deep Underground Neutrino Experiment) aim to solve the remaining questions in neutrino oscillation physics, including neutrinos' mass ordering and CP violation. The near detector(s) will provide crucial constraints on the systematic uncertainties to the oscillation measurements. Flux uncertainty is one of the dominant contributions to the systematic uncertainties. In this talk I present a novel approach of precisely determining the neutrino flux in the near detector(s) of a long-baseline neutrino experiment such as DUNE, by using neutrino/antineutrino-hydrogen interactions with low visible hadronic energy (Low-nu). The application of this method in the proposed KLOE-STT detector is discussed, which could serve as part of the near detector complex of DUNE.

190. Physics Department Summer Lecture Series

"Silicon Detectors for Particle and Nuclear Physics"

Presented by Gabriele Giacomini, BNL

Tuesday, July 9, 2019, 12:30 pm
Small Seminar Room, Bldg. 510

Hosted by: Mary Bishai

Silicon technology is approximately 70 years old but thousands of years by a multitude of researchers has been dedicated to R&D; the well-established microelectronic industry is based on it. Being that the silicon is sensitive to photons (from infrared to X-rays, passing through visible light and ultraviolet) and to charged particles, we can leverage the microelectronic technology to make sensors out of silicon. Silicon sensors are used in a variety of applications including scientific experiments (High Energy Physics, Astrophysics, Photon Science, etc) as well as industrial and commercial use (cameras, etc). The basic structure is the p-n junction across which a voltage is applied. When an ionizing event occurs (a photon or a charged-particle interacting with silicon), a short current pulse (~ few ns) is generated and detected by the read-out electronics. There are many kinds of silicon sensors and each one must be tailored according to the specific application. We'll give an overview of the state of the silicon technology and its different applications.

191. Nuclear Physics Seminar

": Extracting the Heavy-Quark Potential from Bottomonium Observables in Heavy-Ion Collisions"

Presented by Xiaojian Du, Texas A&M University

Tuesday, July 9, 2019, 11 am
Small Seminar Room, Bldg. 510

Hosted by: Rongrong Ma

The in-medium color potential is a fundamental quantity for understanding the properties of the strongly coupled quark-gluon plasma (sQGP). Open and hidden heavy-flavor (HF) production in ultrarelativistic heavy-ion collisions (URHICs) has been found to be a sensitive probe of this potential. Here we utilize a previously developed quarkonium transport approach in combination with insights from open HF diffusion to extract the color-singlet potential from experimental results on Υ production in URHICs. Starting from a parameterized trial potential, we evaluate the Υ transport parameters and conduct systematic fits to available data for the centrality dependence of ground and excited states at RHIC and the LHC. The best fits and their statistical significance are converted into a temperature dependent potential. Including nonperturbative effects in the dissociation rate guided from open HF phenomenology, we extract a rather strongly coupled potential with substantial remnants of the long-range confining force in the QGP.

192. EBNN Directorate Visitor Seminar

"Defense Nuclear Nonproliferation's Mission"

Presented by Dr. Brent K. Park, NNSA - Deputy Administrator for Defense Nuclear Nonproliferation

Monday, July 8, 2019, 3 pm
Large Conference Room, Bldg. 535

Hosted by: Martin Schoonen

193. Office of Educational Programs Event

"QuarkNet Workshop for High School Teachers"

Wednesday, July 3, 2019, 9 am
Building 438

Hosted by: Ketevi Assamagan

194. Physics Department Summer Lecture Series

"Astronomical CCDs and light-sensitive sensors for fast imaging"

Presented by Andrei Nomerotski, BNL

Tuesday, July 2, 2019, 12:30 pm
Small Seminar Room, Bldg. 510

Hosted by: Mary Bishai

I will review how the state-of-the-art sensors developed for astronomical applications can precisely measure the positions and shapes of billions of galaxies. The talk will focus on the camera and sensors for the Large Synoptic Survey Telescope (LSST) and will discuss limitations on the achievable precision coming from the instrumentation. I will also discuss light sensitive sensors which can be used for fast imaging of single photons in QIS and other applications.

195. Nuclear Physics Seminar

"DREENA framework as a multipurpose QGP tomography tool"

Presented by Magdalena Djordjevic, Institute of Physics Belgrade

Tuesday, July 2, 2019, 11 am
Small Seminar Room, Bldg. 510

Hosted by: Jin Huang

High-pt theory and data are traditionally used to explore high-pt parton interactions with QGP, while QGP bulk properties are explored through low-pt data and corresponding models. However, with a proper description of high-pt medium interactions, high-pt probes also become a powerful tool for inferring bulk QGP properties, as they are sensitive to global QGP parameters. With the goal of developing a multipurpose QGP tomography tool, over the past several years, we developed the dynamical energy loss formalism, and the corresponding fully optimized DREENA numerical framework. As first steps towards QGP tomography, we will use DREENA framework to address how we can directly from experimental data i) differentiate between different energy loss mechanisms, ii) infer the shape of QGP droplet. The research presented in this talk will therefore demonstrate how high-pt theory and data can be used to both infer the nature of high pt-parton medium interactions, and important bulk QGP medium properties.

196. Nuclear Physics Seminar

"Charm hadron collective flow and charm hadrochemistry in heavy-ion collisions"

Presented by Xin Dong, Lawrence Berkeley National Laboratory

Tuesday, July 2, 2019, 10 am
Small Seminar Room, Bldg. 510

Hosted by: Lijuan Ruan

Heavy quark transport offers unique insight into the microscopic picture of the sQGP created in heavy-ion collisions. One central focus of heavy quark program is to determine the heavy quark spatial diffusion coefficient and its momentum and temperature dependence. This requires precise measurements of heavy flavor hadron production and their collective flow over a broad momentum region. In the meantime, heavy quark hadrochemistry, the abundance of various heavy flavor hadrons, provides special sensitivity to the QCD hadronization and also plays an important role for the interpretation of heavy flavor hadron data in order to constrain the heavy quark spatial diffusion coefficient of the sQGP. In this seminar, I will focus on the recent STAR results of charm hadron D0, D+/-, D*, Ds, Lambda_c production and D0 radial and elliptic flow in heavy-ion collisions utilizing the state-of-the-art silicon pixel detector, the Heavy Flavor Tracker. These data will be compared to measurements from other experiments at RHIC and the LHC as well as various model calculations. I will then discuss how these data will help us better understand the sQGP properties and its hadronization. Finally, I will present a personal view of future heavy quark measurements at RHIC.

197. Office of Educational Programs Event

"QuarkNet Workshop for High School Teachers"

Tuesday, July 2, 2019, 9 am
Building 438

Hosted by: Ketevi Assamagan

198. Particle Physics Seminar

"Searches of Dark Matter signals with the ATLAS detector at the LHC: Present and future"

Presented by Dr. Rachid Mazini, Academia Sinica, Taiwan

Monday, July 1, 2019, 3 pm
Small Seminar Room, Bldg. 510

Hosted by: Alessandro Tricoli

In this seminar, I will present an overview of up-to-date results on searches for Dark Matter signals with the ATLAS detector at the LHC using Run 2 data. Comparison with non-accelerator DM results as well as interpretation within some theoretical models will be discussed. In addition, expectation from the high-luminosity LHC (HL-LHC) DM searches program will be briefly presented. Finally, I will talk about the new ATLAS High Granularity Timing Detector (HGTD), planned for the phase 2 upgrade program for the HL-LHC run, and it performances for physics studies.

199. Office of Educational Programs Event

"QuarkNet Workshop for High School Teachers"

Monday, July 1, 2019, 9 am
Building 438

Hosted by: Ketevi Assamagan

200. Physics Department Summer Lecture Series

"Using Gravitational Lensing to measure Dark Matter and Dark Energy in the Universe"

Presented by Erin Sheldon, BNL

Friday, June 28, 2019, 12:30 pm
Small Seminar Room, Bldg. 510

Hosted by: Mary Bishai

Gravitational lensing is the bending of the path of light near massive bodies. Mass produces a curvature of space time, and light follows a curved path that is calculable using the General Theory of Relativity. I will discuss how the lensing effect is used to measure the amount of Dark Matter in galaxies and in the universe as a whole. I will also discuss how we use lensing to measure the properties of the mysterious Dark Energy that is driving the accelerated expansion of our universe.

201. Particle Physics Seminar

"First measurement of the neutron-argon cross section between 100 and 800 MeV"

Presented by Prof. Christopher Mauger, University of Pennsylvania

Thursday, June 27, 2019, 3 pm
Small Seminar Room, Bldg. 510

Hosted by: Chao Zhang

The DUNE experiment directs a neutrino beam from Fermilab towards a 40 kiloton liquid argon time-projection chamber (TPC) 1300 km away in the Sanford Underground Research Facility in South Dakota. By measuring electron neutrino and anti-neutrino appearance from the predominantly muon neutrino and anti-neutrino beams, DUNE will determine the neutrino mass ordering and explore leptonic CP violation. The neutrino oscillation phenomena explored by DUNE require robust determinations of the (anti-)neutrino energies by reconstructing the particles produced in charged current reactions. Among the particles emerging from the interaction which carry significant energy, neutrons are the most challenging to reconstruct. The CAPTAIN collaboration has made the first measurement of the neutrino-argon cross section between 100 and 800 MeV of neutron kinetic energy - an energy regime crucial for neutrino energy reconstruction at DUNE. We made the measurement in a liquid argon TPC with 400 kg of instrumented mass. I describe the measurement and discuss future plans.

202. Condensed-Matter Physics & Materials Science Seminar

"Excitonic condensation of strongly correlated electrons"

Presented by Professor Jan Kunes, Vienna University of Technology, Austria

Wednesday, June 26, 2019, 2:30 pm
Bldg. 734, ISB Conference Room 201 (upstairs)

Hosted by: Keith Gilmore

Spontaneous symmetry breaking is a prominent demonstration of the collective behavior of strongly correlated systems. Besides ordering of charge or of spin dipoles, more exotic types of long-range order are possible, which do not couple to conventional probes and are therefore sometimes called the hidden order. Excitonic magnets, or excitonic condensates, are examples of such systems. I will introduce the concept of excitonic condensate from the strong coupling perspective and discuss the rich variety of excitonic phases arising from the internal (spin, orbital) degrees of freedom of the excitons. I will present some numerical results obtained with dynamical mean-field theory for models as well as for specific materials, which we suspect to be excitonic magnets. The presentation will include the recently obtained results for dynamical susceptibilities in phases with long-range order and some proposals on how to detect excitonic condensates with today's experimental techniques.

203. HET Seminar

"Inducing and Detecting Collective Effects of Particle Dark Matter"

Presented by Asher Berlin, SLAC

Wednesday, June 26, 2019, 2:30 pm
Small Seminar Room, Bldg. 510

Hosted by: Gopolang Mohlabeng

Detecting light dark matter that interacts weakly with electromagnetism has recently become one of the benchmark goals of near-term and futuristic direct detection experiments. In this talk, I will discuss an alternative approach to directly detecting such models below the GeV-scale, leveraging on the recent interest and advances in resonant detectors, such as LC circuits.

204. Physics Department Summer Lecture Series

"The Really Big Picture: Cosmology in the 21st Century"

Presented by Paul Stankus, Oak Ridge National Laboratory

Tuesday, June 25, 2019, 12:30 pm
Small Seminar Room, Bldg. 510

Hosted by: Mary Bishai

205. Physics Department Summer Lecture Series

"Search for a new particle in the decay of the Higgs boson"

Presented by Ketevi Assamagan, BNL

Friday, June 21, 2019, 12:30 pm
Small Seminar Room, Bldg. 510

Hosted by: Mary Bishai

In this talk, I will discuss the search strategies that led to the discovery of the Higgs boson. Then, I will focus on the usage of the Higgs boson as a portal to "new physics". I will conclude with dark sector states as a possibility for physics beyond the Standard Model of particle physics

206. Physics Collquium - CANCELLED

"3D imaging of nuclei: status and towards an EIC"

Presented by Kawtar Hafidi, ANL

Tuesday, June 18, 2019, 3:30 pm
Large Seminar Room, Bldg. 510

Hosted by: Thomas Ullrich

207. Physics Department Summer Lecture Series

"Basics of Neutrino Interactions in Matter"

Presented by Milind Diwan, BNL

Tuesday, June 18, 2019, 12:30 pm
Small Seminar Room, Bldg. 510

Hosted by: Mary Bishai

I will review the basics of neutrino interactions in matter with emphasis on calculations of cross sections and rates. The lecture will provide introduction to the physics of weak interactions.

208. Nuclear Physics Seminar

"First observation of the directed flow of D0 and anti-D0 in Au+Au collisions at sqrt(sNN) = 200 GeV"

Presented by Subhash Singha, KSU

Tuesday, June 18, 2019, 11 am
Small Seminar Room, Bldg. 510

Hosted by: Isaac Upsal

In this talk, we will present the first measurement of rapidity-odd directed flow (v1) for D0 and anti-D0 mesons at mid-rapidity (|y| < 0.8) in Au+Au collisions at sqrt(sNN) = 200 GeV using the STAR detector at the Relativistic Heavy Ion Collider. In 10-80% Au+Au collisions, the slope of the v1 rapidity dependence (dv1/dy), averaged over D0 and anti-D0 mesons, is -0.080 +/- 0.017 (stat.) +/- 0.016 (syst.) for transverse momentum (pT) above 1.5 GeV/c. The absolute value of D0-meson dv1/dy is about 25 times larger than that for charged kaons, with 3.4sigma significance. These data not only give unique insight into the initial tilt of the produced matter, they are expected to provide improved constraints for the geometric and transport parameters of the hot QCD medium created in relativistic heavy-ion collisions.

209. Condensed-Matter Physics & Materials Science Seminar

"Tracking phase textures in complex oxides using coherent x-rays"

Presented by Xiaoqian Chen, Lawrence Berkeley Laboratory

Monday, June 17, 2019, 11 am
ISB Bldg. 734, Conf. Rm. 201 (upstairs)

Hosted by: Ian Robinson/Mark Dean

In complex oxides, coupled interactions result in unpredictable and novel emerging orders that are yet to be understood. With the recent advancement in x-ray and laser sources, exploration of equilibrium fluctuation and nonlinear dynamics have become an effective approach to understand these intertwined orders. In particular, coherent x-rays are a simultaneous probe of the order parameter, phase texture, and dynamics. In the first part of my talk, I will use underdoped cuprate La2-xBaxCuO4 as an example to show how x-ray speckle correlation can be a test for (lattice degree of freedom and charge) order coupling and dynamics. However, can we image domain dynamics in real time? In the second part of my talk, I will use antiferromagnetically ordered artificial lattice to demonstrate that phase retrieval lensless imaging can be used to image charge and magnetic orders. Using Bragg coherent diffraction imaging, we revealed a single domain wall motion with 100ms time resolution. References [1] X. M. Chen et al. Phys. Rev. Lett. 117, 167001 (2016) [2] V. Thampy et al. Phys. Rev. B 95, 241111 (2017) [3] X. M. Chen et al. Nat Commun. 10 1435 (2019) [4] X. M. Chen et al. under review, arXiv:1809.05656 [cond-mat.mes-hall]

210. NT/RIKEN Seminar

"D meson mixing via dispersion relation"

Presented by Hsiang-nan Li, National Center for Theoretical Sciences, Physics Division, Taiwan

Friday, June 14, 2019, 2 pm
Building 510, CFNS Room 2-38

Hosted by: Niklas Mueller

In this talk I will explain how to calculate the D meson mixing parameters x and y in the Standard Model. Charm physics is notoriously difficult, because most effective theories and perturbation theories do not apply well. I propose to study the D meson mixing via a dispersion relation, which relates low mass dynamics to high mass one. Taking heavy quark results as inputs in the high mass region, we obtain x and y consistent with experimental data at least in order of magnitude.

211. Physics Department Summer Lecture Series

"The Little Neutral One"

Presented by Mary Bishai, BNL

Friday, June 14, 2019, 12:30 pm
Small Seminar Room, Bldg. 510

Hosted by: Mary Bishai

In the past 50 years, the study of neutrinos, the lightest, yet most abundant of the known elementary particles has revealed cracks in the Standard Model of Particle Physics. Could neutrinos explain the matter anti-matter asymmetry in our Universe? To answer these questions we need to better understand the properties of these elusive polymorphs. I will present a brief history of the neutrino, what we have learnt so far about it, and what we hope to learn in the next couple of decades from some of the most ambitious experiments in particle physics.

212. NSLS-II Friday Lunchtime Seminar

"High resolution strain measurements and phase discrimination in solid solutions using X-Ray Diffuse Multiple Scattering (DMS)"

Presented by Gareth Nisbet, Diamond Light Source, United Kingdom

Friday, June 14, 2019, 12 pm
NSLS-II Bldg. 743 Room 156

Hosted by: Ignace Jarrige

DMS is a new high resolution scattering technique which manifests as diffraction lines impinging on the detector plane, similar to Kikuchi lines or Kossel lines. I will explain how multiple intersections from coplanar and non-coplanar reflections can be used for phase discrimination in multi-phasic systems by following a simple reductive procedure. The methods will be demonstrated using data from complex PMN-PT and PIN-PMN-PT ferroelectric solid solutions. I will also show how convolutional neural networks are being applied to DMS data for phase discrimination.

213. Particle Physics Seminar

"Argon Capture Experiment at DANCE (ACED)"

Presented by Jingbo Wang, UC Davis

Thursday, June 13, 2019, 3 pm
Small Seminar Room, Bldg. 510

Hosted by: Chao Zhang

Liquid argon is becoming a popular medium for particle detection, with applications ranging from low-background dark matter searches to high-energy neutrino detection. Because neutrons may represent both an important source of background and a product of signal events, a good understanding of their interactions in argon is a requirement for precision physics measurements. Despite being one of the most basic quantities needed to describe low energy neutron transport, the thermal neutron capture cross section on argon remains poorly understood, with the existing activation measurements showing significant disagreements. To resolve these disagreements, the Argon Capture Experiment at DANCE (ACED) collaboration has performed a differential measurement of the 40Ar(n, gamma)41Ar cross section using a time of flight neutron beam and the Detector for Advanced Neutron Capture Experiments (DANCE), a ∼4pi gamma spectrometer at Los Alamos National Laboratory. A fit to the differential cross section from 0.015-0.15eV, assuming a 1/v energy dependence, yields sigma(2200)=673+-26 (stat.) +- 59(sys.) mb. During this talk, I will introduce the DUNE experiment before focusing on the importance of neutrons in liquid argon detectors. I will then present the ACED experiment and the use of neutrons as a detector calibration method.

214. Physics Colloquium

"High energy atmospheric neutrinos: connections between laboratory experiments and cosmic rays"

Presented by Mary Hall Reno, University of Iowa

Tuesday, June 11, 2019, 3:30 pm
Large Seminar Room, Bldg. 510

Hosted by: Milind Diwan

The IceCube Neutrino Observatory's measurement of a diffuse flux of neutrinos from astrophysical sources has opened a new era in high energy astroparticle physics. Neutrinos produced by cosmic ray interactions in the atmosphere are the main background to the astrophysical neutrino flux. At these high energies, data from the Large Hadron Collider experiments on heavy flavor production can be used to narrow the uncertainties in the background predictions at the highest energies. Our evaluation of the atmospheric neutrino flux from charm will be used to illustrate how collider physics results are connected to cosmic ray physics in this context.

215. Physics Department Summer Lecture Series

"The Anomalous Magnetic Moment of the Muon and the Standard Model of Particle Physics"

Presented by William Morse, BNL

Tuesday, June 11, 2019, 12:30 pm
Small Seminar Room, Bldg. 510

Hosted by: Mary Bishai

At the end of this lecture, you will know: What is anomalous about the magnetic moment of the muon. What is the magnetic moment of the muon. What is the muon. Why Bohr said "Anyone who thinks they understand Quantum Mechanics, and is not deeply disturbed by it, doesn't understand Quantum Mechanics." What the Standard Model Theorists have to fear from the anomalous magnetic moment of the muon.

216. NSLS-II Friday Lunchtime Seminar

"Status and perspective of high-energy automotive batteries"

Presented by Richard Schmuch, University of Munster, Germany

Friday, June 7, 2019, 12:30 pm
NSLS-II Bldg. 743 Room 156

Hosted by: Ignace Jarrige

This presentation gives an overview of the materials, performance requirements and cost of current automotive traction batteries based on Li-ion technology. It also includes important aspects related to electromobility, such as its sustainability and energy efficiency. As current Li-Ion batteries with intercalation-type active materials are approaching their physicochemical energy density limit of roughly 300 Wh/kg or 800 Wh/L, alternative technologies such as lithium-metal based all-solid-state batteries (ASSBs) currently intensively studied, which promise an energy density of up to 1000 Wh/L. The potential and challenges of this and other post Li-ion batteries (e.g. Dual-Ion, Mg-Ion, Li-Sulphur) are discussed and also compared by systematic bottom-up energy density calculations. Through a step-by-step analysis from theoretical energy content at the material level to practical energies at the cell level, the individual advantages and shortcomings of the studied battery types are elucidated. Literature: (1) Schmuch, R.; Wagner, R.; Hörpel, G.; Placke, T.; Winter, M. Performance and Cost of Materials for Lithium-Based Rechargeable Automotive Batteries. Nat. Energy 2018, 3 (4), 267–278. (2) Betz, J.; Bieker, G.; Meister, P.; Placke, T.; Winter, M.; Schmuch, R. Theoretical versus Practical Energy: A Plea for More Transparency in the Energy Calculation of Different Rechargeable Battery Systems. Adv. Energy Mater. 2018, 1803170, 1803170. (3) Placke, T.; Kloepsch, R.; Dühnen, S.; Winter, M. Lithium Ion, Lithium Metal, and Alternative Rechargeable Battery Technologies: The Odyssey for High Energy Density. J. Solid State Electrochem. 2017, 1–26. (4) Meister, P.; Jia, H.; Li, J.; Kloepsch, R.; Winter, M.; Placke, T. Best Practice: Performance and Cost Evaluation of Lithium Ion Battery Active Materials with Special Emphasis on Energy Efficiency. Chem. Mater. 2016, 28 (20), 7203-7217

217. Physics Department Summer Lecture Series

"Visible and Invisible Clues for New Physics"

Presented by Hooman Davoudiasl, BNL

Friday, June 7, 2019, 12:30 pm
Small Seminar Room, Bldg. 510

Hosted by: Mary Bishai

In this presentation, we will briefly describe the main elements of the Standard Model of particle physics. This theory, together with General Relativity, provides a precise description of a vast array of experimental and observational data, from microscopic to astronomical scales. However, solid empirical evidence and conceptual clues lead us to expect that this "standard" picture is incomplete. We will discuss some of the key reasons for this expectation.

218. Condensed-Matter Physics & Materials Science Seminar

"Probing quantum materials with multiple spectroscopic techniques"

Presented by Eduardo H. da Silva Neto, University of California, Davis

Thursday, June 6, 2019, 1:30 pm
ISB - Bldg. 734

Hosted by: Robert Konik

Resonant X-ray Scattering (RXS), Scanning Tunneling Spectroscopy (STS) and Angle-Resolved Photo-Emission Spectroscopy (ARPES) measurements have been at the forefront of several advances in the studies of quantum materials. Our group specializes in these techniques, looking to leverage their combination to the study of quantum materials. I will discuss two projects where we have used these state-of-the-art techniques to study high-temperature superconductors and topological materials. Charge order has now been ubiquitously observed in cuprate high-temperature superconductors. However, it remains unclear if the charge order is purely static or whether it also features dynamic correlations. I will discuss a polarization-resolved soft x-ray inelastic RXS experiment with unprecedented resolution that demonstrates the existence of a coupling between dynamic magnetic and charge-order correlations in the electron-doped cuprate Nd2−xCexCuO4 [1-3]. I will also discuss a combined ARPES-STS study of the topological material Hf2Te2P. Similar to the reports by H. Ji, et al. on Zr2Te2P [4], band structure calculations and ARPES by Hosen et al. [5] also suggest multiple topological surface states in Hf2Te2P. However, some topological surface states still lacked direct spectroscopic evidence due the inability of ARPES experiments to probe the unoccupied band structure. Using the combination of STS and ARPES with surface K-doping, we probe the unoccupied band structure of Hf2Te2P and demonstrate the presence of multiple surface states with a linear Dirac-like dispersion, consistent with the predictions from previously reported band structure calculations [6]. [1] E. H. da Silva Neto, et al. Science 347, 282 (2015). [2] E. H. da Silva Neto, et al. Science Advances 2 (8), e1600782 (2016). [3] E. H. da Silva Neto, et al. Physical Review B, Rapid Communication 98, 161114(R) (2018). [4] H. Ji, et al. Physical

219. Condensed-Matter Physics & Materials Science Seminar

"Mega-electron-volt ultrafast electron diffraction at SLAC National Accelerator Laboratory"

Presented by Xiaozhe Shen, SLAC National Accelerator Laboratory

Monday, June 3, 2019, 2 pm
Bldg. 480, Conference Room

Hosted by: Jing Tao

Ultrafast electron diffraction (UED) is a transformative tool for probing atomic structural dynamics in ultrafast science to understand the correlation between materials' structure and their functionalities, with the ultimate goal of controlling energy and matter. The advent of high-brightness relativistic electron beams from photocathode radio frequency (RF) gun provides a great opportunity to push the resolving power of UED onto atomic length and time scales. With the expertise in electron beam physics and ultrafast laser technology, SLAC has dedicated enormous efforts to develop a world-leading UED using mega-electron-volt (MeV) electron beams since 2014. Over the years, SLAC MeV UED has achieved great instrument performance and delivered numerous scientific outcomes for ultrafast science. In 2019, SLAC MeV UED has officially transformed into a user facility. In this talk, performance of SLAC MeV UED will be reviewed, including characterization of the instrument resolution and machine stability. The unique capabilities of SLAC MeV UED to accommodate various sample environments for a broad range of scientific interests, including condense matter physics and chemical science, will be presented, with highlighted scientific results. Research and development efforts to improve the performance of SLAC MeV UED will be discussed.

220. Particle Physics Seminar

"Dark matter in the cosmos-The Hunt to Find it in the Laboratory"

Presented by Ioannis (J.D.) Vergados

Friday, May 31, 2019, 11 am
Small Seminar Room, Bldg. 510

Hosted by: Milind Diwan

There is plenty of evidence at all scales (galaxies, cluster of galaxies, cosmological distances) that most of the energy content of the universe is of unknown nature, i.e, 70% is dark energy and 25% dark matter. Only 5% is made up of matter of known nature, in atoms, in stars, in planets etc, constituents predicted by the standard model. Thus unraveling the nature of the dominant components and, in particular, of dark matter is one of the most important open problems in science. This nature can only be understood by the direct detection of its constituents in the laboratory. This can be achieved, if there exists a week interaction, much stronger than gravity, between the dark matter and ordinary matter. The constituents are supposed to have a mass and are called WIMPs (weakly interacting massive particles). We have no idea what this mass is, but from the rotational curves we know that the constituents must be non relativistic, regardless of the size of their mass. The experimental techniques for the direct detection crucially depend on the assumed WIMP mass. Historically the first searches assumed WIMP masses of many GeV and, therefore, heavy nuclear targets were favored. Thus the hunt for DM began and evolved into a multi-pronged and interdisciplinary enterprise, combining cosmology and astrophysics, particle and nuclear physics as well as detector technology, which will be reviewed. Since the WIMP energy is in the keV region, the nucleus cannot be excited and only the nuclear recoil can be measured. As a result, unfortunately, the signal cannot be easily distinguished from backgrounds. After thirty years of intensive work against formidable backgrounds by a lot of large experimental teams, no dark matter has been found. Impressive limits on the nucleon cross section have, however, been obtained. Extension of these searches to GeV or sub-GeV WIMPs is also been considered using light nuclear targets. It may very w

221. Particle Physics Seminar

"Latest oscillation results from the NOvA experiment"

Presented by Diana Patricia Mendez, University of Sussex

Thursday, May 30, 2019, 3 pm
Small Seminar Room, Bldg. 510

Hosted by: Elizabeth Worcester

NOvA is a long-baseline neutrino oscillation experiment measuring $\nu_{\mu}$ disappearance and $\nu_e$ appearance within the NuMI beam from Fermilab. The experiment uses a Near and a Far Detector placed 810 km away from each other and at 14 milliradians off the beam-axis resulting in an observed energy spectrum that peaks at 2 GeV, close to the oscillation maximum. A combined $\bar{\nu}_{\mu}$ + $\nu_{\mu}$ disappearance, and $\bar{\nu}_{e}$ + $\nu_{e}$ appearance result will be presented including NOvA's first collected anti-neutrino data for a total exposure of $16\times10^{20}$ protons-on-target. In addition to an increased exposure, an upgraded analysis has enable the experiment to set new limits to the allowed regions for $\Delta m^2_{32}$ and sin$^2\theta_{23}$ and make a measurement of $\Delta m^2_{32}$ among the world's best.

222. RIKEN Lunch Seminar

"Applications of machine learning to computational physics"

Presented by Dr Akio Tomiya, RBRC

Thursday, May 30, 2019, 12 pm
Building 510, Room 2-160

Hosted by: Yuta Kikuchi

In this talk, I would like to talk about my works with machine learning. I plan to introduce my works which related to lattice QCD research: detection of phase transition in classical spin systems [arXiv 1609.09087, 1812.01522], configuration generation [1712.03893 + some]

223. Environmental & Climate Sciences Department Seminar

"The Influence of Aerosol Chemical Composition, Morphology, and Phase State on Water and Ice Cloud Particle Formation"

Presented by Yue Zhang, North Carolina State, MIT, and Aerodyne

Thursday, May 30, 2019, 11 am
Large Conference Room, Bldg. 490

Hosted by: Ernie Lewis

Aerosols and clouds effect Earth's radiative balance, and aerosol-cloud interactions are major sources of uncertainties in predicting future climate. The climate effects of water and ice cloud particles formed from atmospheric particulate matter are not well understood due to the complex physical and chemical properties of these aerosols. Measurements from fixed sites and field campaigns have shown that organic aerosols (OA) dominate the non-refractory aerosols in the free troposphere where clouds typically form, and cloud water and ice cloud residue both show the presence of organic materials. Despite the abundance of OA, their effects on both cloud condensation nuclei (CCN) and ice nucleation (IN) are not fully understood and even controversial. To probe into these issues, the CCN and IN properties of complex inorganic-organic aerosol mixtures that simulate ambient conditions were measured with a cloud condensation nuclei counter (CCNC, DMT, Inc.) and a spectrometer for ice nucleation (SPIN, DMT, Inc.) at a variety of laboratory conditions. Our studies suggest that the composition of the organic-containing aerosols, as well as their morphology and phase state, jointly impact their cloud forming potential. The results highlight the importance of combining aerosol physical and chemical properties to accurately understand cloud particle formation processes and their implications on the climate.

224. HET Seminar

"Visualization Tools and the B-anomalies"

Presented by German Valencia, Monash University

Wednesday, May 29, 2019, 2:30 pm
Small Seminar Room, Bldg. 510

Hosted by: Sally Dawson

225. Nuclear Physics Seminar

"Examining hydrodynamical modelling of the QGP through dilepton radiation"

Presented by Gojko Vujanovic, Wayne State University

Tuesday, May 28, 2019, 11 am
Small Seminar Room, Bldg. 510

Hosted by: Rongrong Ma

Recent viscous hydrodynamical studies at the Relativistic Heavy-Ion Collider (RHIC) and the Large Hadron Collider (LHC), show that bulk viscosity plays an important role in their phenomenological description. A temperature-dependent bulk viscosity in the hydrodynamical evolution of the medium can modify the development of the hydrodynamic momentum anisotropy differently in the high- and low-temperature regions. Thus, anisotropic flow coefficients of various particle species are affected differently depending where their surface of last scattering lies. For the case of hadronic observables, they are predominantly sensitive to low temperature regions, while electromagnetic radiation is emitted at all temperatures. Therefore, bulk viscosity should affect electromagnetic radiation differently than hadron emission. The effects of bulk viscosity on one of the electromagnetic probes, namely photons, has already been investigated. The same statement holds true for hadrons. The goal of this presentation is to study how dilepton production, the other source of electromagnetic radiation, gets modified owing to the presence of bulk viscosity at RHIC and LHC energies. With calculations at different collision energies, comparisons in the dilepton signal can be made and more robust conclusions regarding the role of bulk viscosity in high energy heavy-ion collisions can be drawn. Dilepton radiation from the dilute hadronic sector of the medium, which are radiated in addition to dileptons emitted during the hydrodynamical evolution, will also be included to ascertain whether interesting dynamics induced by bulk viscosity may have observable consequences. To complete that investigation, particular attention will be given to how the $\rho(770)$ meson, and its subsequent dilepton decay, is calculated at the end of the hydrodynamical simulation.

226. NT/RIKEN Seminar

"Pieces of the Puzzle: Reaching QCD on Quantum Computers"

Presented by Henry Lamm, UMD

Friday, May 24, 2019, 2 pm
Building 510, CFNS Seminar Room 2-38

Hosted by: Niklas Mueller

The advent of quantum computing for scientific research presents the possibility of calculating time-dependent observables like viscosity and parton distributions from QCD. In order to utilize this new tool, a number of theoretical and practical issues must be addressed related to efficiently digitize, initialize, propagate, and evaluate quantum field theory. In this talk, I will discuss a number of projects being undertaken by the NuQS collaboration to realize calculations on NISQ era and beyond quantum computers.

227. HET Lunch Discussion

"Partial Neutrino Decay Resolves IceCube's Track and Cascade Tension"

Presented by Peter Denton, BNL

Friday, May 24, 2019, 12:15 pm
Building 510, Room 2-160

228. CFNS Seminar

"Effect of non-eikonal corrections on two particle correlations"

Presented by Tolga Altinoluk, National Centre for Nuclear Research, Warsaw, Poland

Thursday, May 23, 2019, 4 pm
Building 510, CFNS Room 2-38

Hosted by: Andrey Tarasov

We will discuss the non-eikonal effects on gluon production in pA collisions that originate from the finite longitudinal width of the target. We will then consider the dilute target limit, and discuss the single and double inclusive gluon production cross section in pp collisions. We will show that non-eikonal corrections break the accidental symmetry of the CGC and give rise to non-vanishing odd azimuthal harmonics.

229. Condensed-Matter Physics & Materials Science Seminar

"In situ imaging of gold nanocrystals during the CO oxidation reaction studied by Bragg Coherent Diffraction Imaging"

Presented by Ana Flavia Suzana, Brazilian Association of Synchrotron Light Technology-ABTLUS, Brazil

Thursday, May 23, 2019, 1:30 pm
ISB Bldg. 734, Conf. Rm. 201 (upstairs)

Hosted by: Ian Robinson

The fundamental aim of heterogeneous catalysis research is to understand mechanisms at the nanoparticle level, and then to design and synthesize catalysts with desired active sites. In this regard, the in situ/operando characterization of defects is crucial as they are preferential catalytic sites for the reaction occurrence. In this seminar I will talk about the main part of the work developed during my PhD: the investigation of the morphology and structure evolution of gold nano-catalysts supported on titanium dioxide. Those catalytic materials were evaluated for the model CO oxidation reaction, chosen for its environmental relevance and "simplicity" to be reproducible within our X-ray imaging study. We used the Bragg Coherent Diffraction Imaging technique to follow in situ the 3D morphology changes under catalytic reaction conditions. We correlated the 3D displacement field and strain distribution of the gold nanoparticles to the catalytic properties of the material. In particular, for a 120 nm gold nanoparticle, we quantified under working conditions the adsorbate-induced surface stress on the gold nanocrystal, which leads to restructuration and defects identified as a nanotwin network.

230. RIKEN Lunch Seminar

"Complex saddle points of path integrals"

Presented by Semeon Valgushev, BNL

Thursday, May 23, 2019, 12 pm
Building 510, Room 2-160

Hosted by: Yuta Kikuchi

In this talk, we discuss the physical role of complex saddle points of path integrals. In the first case study, we analyze saddle point structure of two-dimensional lattice gauge theory represented as Gross-Witten-Wadia unitary matrix model. We find that non-perturbative physics in the strong coupling phase can be understood in terms of new family of complex saddle points those properties are connected to resurgent structure of the 1/N expansion. In the second case study, we discuss the sign problem in fermionic systems at finite density and the possibility to alleviate it with the help of defomations of integration contour into complex space on the example of two-dimensional Hubbard model.

231. Chemistry Department Seminar

"Designing Dopants to Shield Anion Electrostatics in Doped Conjugated Polymers to Obtain Highly Mobile and Delocalized Carriers"

Presented by Taylor Aubry, UCLA

Thursday, May 23, 2019, 11 am
Room 300, 3rd Floor - Chemistry Bldg. 555

Hosted by: Matthew Bird

Doping conjugated polymers is an effective way to tune their electronic properties for thin-film electronics applications. Chemical doping of semiconducting polymers involves the introduction of a strong electron acceptor or donor molecule that can undergo charge transfer (CT) with the polymer. The CT reaction creates electrical carriers on the polymer chain (usually positive polarons a.k.a. holes) while the dopant molecules remain in the film as counterions. Undesirably, strong electrostatic attraction from the anions of most dopants will localize the polarons and reduce their mobility. We employ a new strategy utilizing substituted icosahedral dodecaborane (DDB) clusters as molecular dopants for conjugated polymers. DDBs provide a unique system in which the redox potential of the dopant can be rationally tuned via modification of the substituents without significant change to the size or shape of the dopant molecule. These clusters allow us to disentangle the effects of energetic offset on the production of free and trapped carriers in DDB-doped poly-3-hexylthiophene (P3HT) films. We find that by designing our cluster to have a high redox potential and steric protection of the core-localized electron density, highly delocalized polarons with mobilities equivalent to films doped with no anions present are obtained.1 P3HT films doped with these boron clusters have conductivities and polaron mobilities roughly an order of magnitude higher than films doped with conventional small-molecule dopants such as 2,3,5,6-tetrafluoro-7,7,8,8- tetracyanoquinodimethane (F4TCNQ). The spectral shape of the IR-region absorption for our DDB-doped polymer film closely matches the calculated theoretical spectrum for the anion at infinite distance from the polaron.2 We therefore conclude that these DDB clusters are able to effectively spatially separate the counterion. Moreover, nearly all DDB-produced carriers are free, while it has been shown that small m

232. C-AD Accelerator Physics Seminar

"High-Level Software Development for the CLARA FEL Test Facility"

Presented by Dr. James Jones, Daresbury Laboratory

Wednesday, May 22, 2019, 3 pm
Bldg. 911B, Second Floor, Large Conf. Rm., Rm. A2

Hosted by: Steve Peggs

CLARA is a low-energy test facility for advanced FEL physics and beam-driven novel acceleration techniques. As part of the facility we have planned for an advanced integrated system for high-level software development and online-model based on C++ and python interfaces. An overview of the CLARA facility and recent experimental results will be presented along with a description and current status of the HLS middle-layer and online-model. Future plans for CLARA will also be presented.

233. Nuclear Physics Seminar

"Future opportunities for a small-system scan at RHIC"

Presented by Jiangyong Jia

Tuesday, May 21, 2019, 11 am
Small Seminar Room, Bldg. 510

Hosted by: Rongrong Ma

The observation of multi-particle azimuthal correlations in high-energy small-system collisions has led to intense debate on its physical origin between two competing theoretical scenarios: one based on initial-state intrinsic momentum anisotropy (ISM), the other based on final-state collective response to the collision geometry (FSM). To complement the previous scan of asymmetric collision systems (p+Au, d+Au and He+Au), we propose a scan of small symmetric collision systems at RHIC, such as C+C, O+O, Al+Al and Ar+Ar at sqrt{s_NN} = 0.2 TeV, to further disentangle contributions from these two scenarios. These symmetric small systems have the advantage of providing access to geometries driven by the average shape of the nuclear overlap, compared to fluctuation-dominant geometries in asymmetric systems. A transport model is employed to investigate the expected geometry response in the FSM scenario. Different trends of elliptic flow with increasing charge particle multiplicity are observed between symmetric and asymmetric systems, while triangular flow appears to show a similar behavior. Furthermore, a comparison of O+O collisions at sqrt{s_NN} = 0.2 TeV and at sqrt{s_NN} =2.76−7 TeV, as proposed at the LHC, provides a unique opportunity to disentangle the collision geometry effects at nucleon level from those arising from subnucleon fluctuations.

234. HET Lunch Discussion

"Update on Double Higgs Production"

Presented by Sally Dawson, BNL

Friday, May 17, 2019, 12:15 pm
Building 510, Room 2-160

Hosted by: Peter Denton

235. NSLS-II Friday Lunchtime Seminar

"MAXPD: Multi-Anvil X-ray Powder Diffraction — COMPRES Partner User Program for High Pressure Studies at 28-ID-2-D"

Presented by Matthew L. Whitaker, Stony Brook University

Friday, May 17, 2019, 12 pm
NSLS-II Bldg. 743 Room 156

Hosted by: Ignace Jarrige

MAXPD is the downstream endstation of XPD, an insertion device beamline at Sector 28 (28-ID-2-D) of NSLS-II. The MAXPD endstation and General User Program are sponsored by the COnsortium for Materials Properties Research in Earth Sciences (COMPRES). MAXPD has an 1100-ton hydraulic press installed, which is equipped with a unique DT-25 pressure module that can be swapped out for a more standard D-DIA module as desired. MAXPD makes use of the world-class monochromatic beam available at XPD (usually ~67 keV), with which we collect both angular dispersive X-ray diffraction data and X-radiographic imaging. The first General User experiments took place in March 2018. Final Science Commissioning beamtime took place in August of last year, and the full General User program for MAXPD began in the 2018-3 cycle. In this seminar, I will give an overview of the science drivers behind the development of the endstation, some of its unique capabilities, some representative results from recent experiments conducted over the last two cycles at MAXPD, and where we are looking to go as we look to the future.

236. NT/RIKEN Seminar

"The non-equilibrium attractor: Beyond hydrodynamics"

Presented by Michael Strickland, Kent State University

Friday, May 10, 2019, 2 pm
Building 510, CFNS Seminar Room 2-38

Hosted by: Niklas Mueller

237. HET Seminar - CANCELLED

Presented by Nirmal Raj, Triumf

Friday, May 10, 2019, 12:15 pm
Building 510, Room 2-160

Hosted by: Gopolang Mohlabeng

238. RIKEN Lunch Seminar

"Electric dipole moments in the era of the LHC"

Presented by Jordy de Vries, University of Massachusetts Amherst, Riken BNL

Thursday, May 9, 2019, 12 pm
Building 510, Room 2-160

Hosted by: Yuta Kikuchi

The search for an understanding of fundamental particle physics that goes beyond the Standard Model (SM) has grown into a worldwide titanic effort. Low-energy precision experiments are complementary to collider searches and, in certain cases, can even probe higher energy scales directly. However, the interpretation of a potential signal, or lack thereof, is complicated because of the non-perturbative nature of low-energy QCD. I will use the search for electric dipole moments (EDMs), which aims to discover beyond-the-SM CP violation, as an example to illustrate these difficulties and how they can be overcome by combining (chiral) effective field theory and lattice QCD. I discuss how EDM experiments involving complex systems like nucleons, nuclei, atoms, and molecules constrain possible CP-violating interactions involving the Higgs boson, how these constraints match up to direct LHC searches, and the relevance of and strategies for the improvement of the hadronic and nuclear theory.

239. Environmental & Climate Sciences Department Seminar

"High-throughput field phenotyping of photosynthetic capacity using hyperspectral imaging"

Presented by Katherine Meacham, Univ. of Illinois

Thursday, May 9, 2019, 11 am
Large Conference Room, Bldg. 490

Hosted by: Angie Burnett

Improved photosynthetic rates have been shown to increase crop biomass, making improved photosynthesis a focus for driving future grain yield increases. Improving the photosynthetic pathway offers opportunity to meet food demand, but requires high throughput measurement techniques to detect photosynthetic variation in natural accessions and transgenically improved plants. Gas exchange measurements are the most widely used method of measuring photosynthesis in field trials but this process is laborious and slow, and requires further modeling to estimate meaningful parameters and to upscale to the plot or canopy level. In field trials of tobacco with modifications made to the photosynthetic pathway, we infer key photosynthetic parameters from imaging spectroscopy using a partial least squares regression technique. We used two hyperspectral cameras with resolution 2.1nm in the visible range and 4.9nm in the NIR. Ground-truth measurements from leaf-level photosynthetic gas exchange, full-range (400-2500nm) hyperspectral reflectance and extracted pigments support the model. The results from a range of wild-type cultivars and from genetically modified germplasm offer a high-throughput screening tool for crop trials aimed at identifying increased photosynthetic capacity.

240. Physics Colloquium

"Mu*STAR Accelerator-Driven Subcritical Molten-Salt All-Purpose non-Nuclear Reactor"

Presented by Rolland Johnson, Muons Inc.

Tuesday, May 7, 2019, 3:30 pm
Large Seminar Room, Bldg. 510

Hosted by: George Redlinger

The Mu*STAR BHAG[1] is: To make superconducting RF accelerators so powerful and efficient that they make enough neutrons to produce nuclear energy for electricity or for process heat at less cost than from wind, solar, or natural gas, without weapons proliferation legacies of enrichment and chemical reprocessing, by burning unwanted nuclear materials. The arguments are presented to support that such a goal is possible in the near future. [1] BHAG: Big Hairy Audacious Goal, from "Built to Last: Successful Habits of Visionary Companies" by Jim Collins and Jerry Porras (2004)

241. NT/RIKEN Seminar

"Relativistic Hydrodynamic Fluctuations"

Presented by Gokce Basar, UiC

Friday, May 3, 2019, 2 pm
Small Seminar Room, Bldg. 510

Hosted by: Niklas Mueller

We present a general systematic formalism for describing dynamics of fluctuations in an arbitrary relativistic hydrodynamic flow, including their feedback (known as long-time hydrodynamic tails) in a deterministic way. The fluctuations are described by two-point equal-time correlation functions. We introduce a definition of equal time in a situation where the local rest frame is determined by the local flow velocity, and a method of taking derivatives and Wigner transforms of such equal-time correlation functions, which we call confluent. The Wigner functions satisfy evolution equations that describes the relaxation of the out-of-equilibrium modes. We find that the equations for confluent Wigner functions nontrivially match with the kinetic equation for phonons propagating on an arbitrary background, including relativistic inertial and Coriolis forces due to acceleration and vorticity of the flow. We also describe the procedure of renormalization of short-distance singularities which eliminates cutoff dependence, allowing efficient numerical implementation of these equations.

242. HET Lunch Discussion

"Ultra-Light Boson Dark Matter and Event Horizon Telescope Observations of M87"

Presented by Hooman Davoudiasl

Friday, May 3, 2019, 12:15 pm
Building 510, Room 2-160

Hosted by: Aaron Meyer

243. Special Particle Physics Seminar

"Observation of CP violation in charm decays"

Presented by Angelo Di Canto, BNL

Friday, May 3, 2019, 11 am
Small Seminar Room, Bldg. 510

Hosted by: Chao Zhang

The existence of CP violation in the decays of strange and beauty mesons is well established experimentally by numerous measurements. By contrast, CP violation in the decays of charm particles has so far escaped observation. This seminar reports on the first observation of CP violation in charm decays thought the measurement of the difference between the time-integrated CP asymmetries in D0 -> K- K+ and D0 -> pi- pi+ decays. The measurement has been performed using the full data set of proton-proton collisions collected by LHCb in 2011-2018, which corresponds to an integrated luminosity of 9fb-1. In addition, a brief overview of recent measurements of mixing and mixing-induced CP violation in charm mesons at LHCb is also presented.

244. Particle Physics Seminar

"Dark Matter Searches with the ATLAS Detector at the LHC"

Presented by Arely Cortes Gonzalez, CERN

Thursday, May 2, 2019, 3 pm
Small Seminar Room, Bldg. 510

Hosted by: Michael Begel

The presence of a non-baryonic dark matter component in the Universe is inferred from the observation of its gravitational interaction. If dark matter interacts weakly with the Standard Model it would be produced at the LHC, escaping the detector and leaving a large missing transverse momentum as their signature. The ATLAS detector has developed a broad and systematic search program for dark matter production in LHC proton-proton collisions. The results of these searches on the 13 TeV data, their interpretation, and the possible evolution of the search program will be presented.

245. RIKEN Lunch Seminar

"The Chiral Qubit: quantum computing with chiral anomaly"

Presented by Dmitri Kharzeev, Stony Brook University and BNL

Thursday, May 2, 2019, 12 pm
Building 510, Room 2-160

Hosted by: Yuta Kikuchi

The quantum chiral anomaly enables a nearly dissipationless current in the presence of chirality imbalance and magnetic field – this is the Chiral Magnetic Effect (CME), observed recently in Dirac and Weyl semimetals. We propose to utilize the CME for the design of qubits potentially capable of operating at THz frequency, room temperature, and the coherence time to gate time ratio of about 10^4 . The proposed "Chiral Qubit" is a micron-scale ring made of a Weyl or Dirac semimetal, with the |0> and |1> quantum states corresponding to the symmetric and antisymmetric superpositions of quantum states describing chiral fermions circulating along the ring clockwise and counter-clockwise. A fractional magnetic flux through the ring induces a quantum superposition of the |0> and |1> quantum states. The entanglement of qubits can be implemented through the near-field THz frequency electromagnetic fields.

246. HET Seminar

"Unification and Precision Measurements"

Presented by James Wells, University of Michigan

Wednesday, May 1, 2019, 2:30 pm
Small Seminar Room, Bldg. 510

Hosted by: Sally Dawson

247. Nuclear Physics Seminar

"Reviewing the AGS Heavy Ion Program and Looking Forward to the Fixed-Target Program at STAR"

Presented by Prof. Daniel Cebra, UC Davis

Tuesday, April 30, 2019, 11 am
Small Seminar Room, Bldg. 510

Hosted by: Rongrong Ma

In the 1980's and 90's the AGS initiated a heavy-ion beam program with both silicon and gold beams. A suite of dedicated experiments established the systematics for production of light charged particles, strangeness, light nuclei, and anti-particles, as well as systematics for flow and femtoscopy. Those experiments established the design of the RHIC detectors and trained the personnel who would become leaders in the RHIC program. Recently, there has been renewed interest in the energy region covered by the AGS heavy-ion program. New facilities are being built Germany and Russia and proposed in Japan and China. And a conclusion of the first beam energy scan at RHIC was that it would be necessary to revisit the AGS energy range by installing a fixed-target within the STAR experiment. This talk will review key results from the AGS heavy-ion program, and those to results from the STAR fixed-target test runs, and outline the proposed physics program.

248. Particle Physics Seminar

""Measure what is measurable and make measurable what is not so - Uncover new physics with bosons at the LHC and upgrades of the CMS detector to maximize the discovery potential""

Presented by Mia Liu, FNAL

Monday, April 29, 2019, 11 am
Small Seminar Room, Bldg. 510

Hosted by: Alessandro Tricoli

The Standard Model describes the building blocks of matter and their interactions. It has been tested extensively with experimental data and found to be incredibly successful in describing nature. Discovering the Higgs boson in 2012 at the LHC completed the picture of the SM. The LHC is at the forefront of directly searching for new physics which is Beyond-Standard-Model (BSM), and I will discuss searches for supersymmetric partners of the electroweak bosons, as well as measurement of an extremely rare process with three WWW bosons as stringent tests of the SM. I will also discuss the instrumentation which enables such studies. The discussion includes the recently completed CMS Phase-1 pixel upgrade, as well as the R&D studies towards solving the future trigger and computing challenges using innovative machine learning approaches in future high energy experiments.

249. Particle Physics Seminar

"Searching for Higgs Pair Production at the LHC"

Presented by Elizabeth Brost, Northern Illinois University

Thursday, April 25, 2019, 3 pm
Small Seminar Room, Bldg. 510

Hosted by: Alessandro Tricoli

Since the discovery of the Higgs boson in 2012, the particle physics community at the Large Hadron Collider (LHC) has been hard at work studying its properties, and comparing them to the predictions of the Standard Model (SM), including the couplings of the Higgs boson to itself and to other particles. The Higgs self-coupling can be measured directly in the Higgs pair production process, and will provide insight into the nature of electroweak symmetry breaking. In the SM, the di-Higgs cross section in proton-proton collisions is very small. However, a wide range of beyond-the-SM models predict enhancements to the di-Higgs production rate, which motivates searching for di-Higgs production even now, when the SM cross section is too small to measure in the current LHC dataset. Looking forward, the LHC Run 3 and HL-LHC will bring a new set of challenges, including more proton-proton collisions per bunch crossing. Extracting rare physics signatures from this busier environment will be difficult for the current ATLAS trigger system. In this talk, I will present current and future ATLAS searches for hh production using a variety of final states, and discuss the use of future track triggers in upgrades to the ATLAS trigger system.

250. RIKEN Lunch Seminar

"Partons from the Path-Integral Formalism of the Hadronic Tensor"

Presented by Keh-Fei Liu, University of Kentucky

Thursday, April 25, 2019, 12 pm
Building 510, Room 2-160

Hosted by: Yuta Kikuchi

251. NT/RIKEN Seminar

"Parton distributions in Euclidean space"

Presented by Anatoly Radyushkin, ODU/JLab

Friday, April 19, 2019, 2 pm
Building 510, CFNS Room 2-38

Hosted by: Niklas Mueller

To extract parton distributions from the lattice simulations, one needs to consider matrix elements M(z,p) of bilocal correlators of parton fields [generically written as φ(0)φ(z)] at spacelike separations z=(0,0,0,z_3). A transition to PDFs may be proceeded by taking a Fourier transform either with respect to z_3 for fixed p_3 (which gives X. Ji's quasi-PDFs), or with respect to the Lorentz-invariant variable ν=-(zp) for fixed values of another Lorentz invariant z^2 [which results in pseudo-PDFs].These functions are interesting on their own, and I will discuss, in the continuum case, their general properties, the connection between the two types of functions, and their relation with the usual light-cone PDFs. I will outline the algorithm of extracting the PDFs through the use of the so-called "reduced Ioffe-time distributions",and illustrate this pseudo-PDF-oriented approach on the example of exploratory lattice simulations performed by Orginos et al.

252. Particle Physics Seminar

"Dissecting the Higgs boson with ATLAS and leptons"

Presented by Quentin Buat, CERN

Thursday, April 18, 2019, 3 pm
Small Seminar Room, Bldg. 510

Hosted by: Alessandro Tricoli

Using data taken during the first years of the LHC Run2, ATLAS has firmly established the coupling of the Higgs boson to the tau lepton, thus directly confirming the existence of leptonic Yukawa interactions. In this talk, I will present the cross-section measurements performed by ATLAS in the di-tau final state with a partial Run2 dataset and discuss the prospects of the analysis with the full Run2 dataset and beyond. I will also discuss the status of the search for the muonic Yukawa interaction.

253. Condensed-Matter Physics & Materials Science Seminar

""Superconductivity and magnetism at ferroelectric critical point""

Presented by Alexander Balatsky, UConn Nordita

Thursday, April 18, 2019, 1:30 pm
ISB Bldg. 734 Conf. Rm. 201 (upstairs)

Hosted by: Ilya Drozdov

It is well established that multiple entangled orders emerge in quantum materials at criticality: eg superconducting states develop in the vicinity of magnetic phases. I will make the case that similar phenomena occur in quantum paraelectrics. Recent observations of strain and O18 isotope substitution in doped STO support the view of the key role critical ferroelectric fluctuations play in producing superconductivity. Looking beyond superconductivity, I will illustrate how quantum ferroelectric fluctuations can induce magnetic fluctuations due to recently proposed phenomenon of dynamic multiferroicity.

254. Environmental & Climate Sciences Department Seminar

"Using High-Resolution Observations to Improve a Low-Resolution Global Climate Model"

Presented by Greg Elsaesser, NASA GISS

Thursday, April 18, 2019, 11 am
Large Conference Room, Bldg. 490

Hosted by: Mike Jensen

This talk will begin with an overview of recent development in the representation of deep convection in the NASA Goddard Institute for Space Studies (GISS) General Circulation Model (GCM). Global satellite remote sensing products are important references for continual GCM development and evaluation, but such products often provide data at coarse temporal and/or spatial resolutions, thus making it difficult to conceptualize and evaluate "process representations" in a GCM. I will discuss the various approaches I am taking to average global satellite retrievals in new ways, coincident with efforts to use new DOE/ARM observations, to derive composite high-resolution evolutions of deep convection and the nearby environment. These depictions will not only inform future development, but they are also crucial for ensuring that recent improved mean-state representations are not the result of errors cancelling at the process level.

255. HET Seminar

"Cores in Dwarf Galaxies from Fermi Repulsion"

Presented by James Unwin, University of Illinois, Chicago

Wednesday, April 17, 2019, 2:30 pm
Small Seminar Room, Bldg. 510

Hosted by: Sally Dawson

256. Nuclear Physics Seminar

"Recent Results from COMPASS"

Presented by Ana-Sofia Nunes, BNL

Tuesday, April 16, 2019, 11 am
Small Seminar Room, Bldg. 510

Hosted by: Oleg Eyser

COMPASS is a fixed target experiment at the CERN SPS that has been collecting data since 2002 and was already approved to run in 2021. It uses unique beams of naturally polarized muons and unpolarized hadrons of 160, 190 or 200 GeV impinging on polarized and unpolarized proton, isoscalar or heavy targets to study fundamental aspects of QCD, as the structure of nucleons, hadron spectroscopy and the pion polarizability. The collected data allow measurements on the spin structure of nucleons, not only in the collinear approximation but also on nucleon tomography, either via deeply virtual Compton scattering (DVCS) and deeply virtual meson production (DVMP) which give access to generalized parton distributions (GPDs), or via semi-inclusive deep inelastic scattering (SIDIS) and polarized Drell-Yan (DY) which give access to transverse-momentum dependent parton distribution functions (TMDs). Moreover, hadron multiplicities extracted from semi-inclusive deep inelastic scattering data can be used as input for the computation of fragmentation functions (FFs) in QCD fits. A selection of the latest published and preliminary results of COMPASS in the scope of the study of the structure of nucleons and the hadronization of quarks will be presented.

257. Condensed Matter Physics and Materials Science - The Myron Strongin Seminar

"Disappearance of Superconductivity Due to Vanishing Coupling in the Overdoped High-Temperature Cuprate Superconductors"

Presented by Tonica Valla, BNL

Monday, April 15, 2019, 1:30 pm
ISB Bldg. 734, Conf. Rm. 201 (upstairs)

Hosted by: Weiguo Yin and Jing Tao

In high-temperature cuprate superconductors, superconductivity is accompanied by a "plethora of orders", and phenomena that may compete, or cooperate with superconductivity, but which certainly complicate our understanding of origins of superconductivity in these materials. While prominent in the underdoped regime, these orders are known to significantly weaken or completely vanish with overdoping. Here, we approach the superconducting phase from the more conventional highly overdoped side. We present angle-resolved photoemission spectroscopy (ARPES) studies of Bi2Sr2CaCu2O8+d (Bi2212) single crystals cleaved and annealed in ozone to increase the doping all the way to the metallic, non-superconducting phase. We show that the mass renormalization in the antinodal region of the Fermi surface, associated with the structure in the quasiparticle self-energy, that possibly reflects the pairing interaction, monotonically weakens with increasing doping and completely disappears precisely where superconductivity disappears. This is the direct evidence that in the overdoped regime, superconductivity is determined by the coupling strength. A strong doping dependence and an abrupt disappearance above the transition temperature (Tc) eliminate the conventional phononic mechanism of the observed mass renormalization and identify the onset of spin-fluctuations as its likely origin.

258. Physics Colloquium

"Future Circular Collider"

Presented by Michael Benedikt, CERN

Friday, April 12, 2019, 3:30 pm
Large Seminar Room, Bldg. 510

Hosted by: George Redlinger & Maria Chamizo Llatas

The global Future Circular Collider Study, launched in 2014 by CERN as host institute, has published its conceptual design report by the end of 2018, as input to the update of the European Strategy for Particle Physics. Today, a staged Future Circular Collider (FCC), consisting of a luminosity-frontier highest-energy electron-positron collider (FCC-ee) followed by an energy-frontier hadron collider (FCC-hh), promises the most far-reaching physics program for the post-LHC era. FCC-ee is a precision instrument to study the Z, W, Higgs and top particles, and o?ers unprecedented sensitivity to signs of new physics. Most of the FCC-ee infrastructure can later be reused for the subsequent hadron collider, FCC-hh. The FCC-hh provides proton-proton collisions at a centre-of-mass energy of 100 TeV and can directly produce new particles with masses of up to several tens of TeV. This collider will also measure the Higgs self-coupling and explore the dynamics of electroweak symmetry breaking. Heavy-ion collisions and ep collisions (FCC-eh) further contribute to the breadth of the overall FCC program. The integrated FCC infrastructure will serve the particle physics community through the end of the 21st century. This presentation will summarize the conceptual designs of FCC-ee and FCC-hh, covering the machine concepts, the R&D for key technologies, infrastructure planning, initial considerations for the experiments, and a possible implementation schedule.

259. NT / RIKEN Seminar

"A Complex Path Around the Sign Problem"

Presented by Paolo Bedaque, U Maryland

Friday, April 12, 2019, 2 pm
Building 510, CFNS Seminar Room 2-38

Hosted by: Niklas Mueller

The famous "sign problem" is the main roadblock in the path to a Monte Carlo solution of QCD at finite densities and the study of real time dynamics. We review a recent developed approach to this problem based on deforming the domain of integration of the oath integral into complex field space. After discussing the math involved in the complex analysis of multidimensional spaces we will talk about the advantages/disadvantages of using Lefschetz thimbles, "learnifolds" and "optimized manifolds" as the alternative integration manifold as well as the algorithms that go with them. Several examples of lower dimensional field theories will be presented.

260. HET Lunch Seminar

"Highlights from EW Moriond 2019"

Presented by Amarjit Soni, BNL

Friday, April 12, 2019, 12 pm
Building 510, Room 2-160

Hosted by: Aaron Meyer

261. Particle Physics Seminar

"Neutrino Interaction Modeling and Tuning"

Presented by Libo Jiang, University of Pittsburgh

Thursday, April 11, 2019, 3 pm
Small Seminar Room, Bldg. 510

Hosted by: Mary Bishai

GENIE is a well-knows event generator provides the simulation of neutrino interactions, and performs a highly-developed global analysis of neutrino scattering. It handles all neutrinos and targets, and all processes relevant from MeV to PeV energy scales. I am going to present the modelling of neutrino interactions and results of tuning against experimental data.

262. Condensed-Matter Physics & Materials Science Seminar

"Tailoring electronic and thermal properties of bulk Cu26T2(Ge,Sn)6S32 colusite through defects engineering and functionalization of the conductive network"

Presented by Emmanuel Guilmeau, CRISMAT Laboratory, Caen, France

Thursday, April 11, 2019, 1:30 pm
Bldg. 734, ISB Conference Room 201 (upstairs)

Hosted by: Qiang Li

A complete study of the structure and thermoelectric properties of colusite Cu26T2(Ge,Sn)6S32 (T = V, Cr, Mo, W) is presented. A brief introduction provides a state-of-theart/survey of thermoelectric sulfides, with a special focus on the structural features and transport properties relationship in Cu-based sulfides. In the first part of this presentation, we highlight the key role of the densification process on the formation of short-to-medium range structural defects in Cu26V2Sn6S32 [1]. A simple and powerful way to adjust carrier concentration combined with enhanced phonon scattering through point defects and disordered regions is described. By combining experiments with band structure and phonons calculations, we elucidate, for the first time, the underlying mechanisms at the origin of the intrinsically low thermal conductivity in colusite samples as well as the effect of S vacancies and antisite defects on the carrier concentration. In the second part, we demonstrate the spectacular role of the substitution of V5+ by hexavalent T6+ cations (Cr, Mo and W) on the electronic properties, leading to high power factors [2]. In particular, Cu26Cr2Ge6S32 shows a value of 1.53 mW m-1 K-2 at RT that reaches a maximum value of 1.94 mW m-1 K-2 at 700 K. The rationale is based on the concept of conductive "Cu-S" network, which in colusites corresponds to the more symmetric parent sphalerite structure. The interactions within the mixed octahedral-tetrahedral [TS4]Cu6 complexes are shown to be responsible for the outstanding electronic transport properties. [1] C. Bourgès et al., J. Amer. Chem. Soc. 140 (2018) 2186 [2] V. Pavan Kumar et al., Adv. Energy Mater. 9 (2019) 1803249

263. Condensed-Matter Physics & Materials Science Seminar

"Importance of electron interactions in understanding the photo-electron spectroscopy and the Weyl character of MoTe2"

Presented by Niraj Aryal, Florida State University

Thursday, April 11, 2019, 11 am
ISB Bldg. 734 Conference Room 201 (upstairs)

Hosted by: Weiguo Yin

Weyl semimetals are crystalline materials that host pairs of chiral Weyl Fermions (WFs) as low energy excitations. Such WFs act as sources and sinks of Berry curvature and can contribute to many exotic transport properties. Recently, inversion symmetry broken transition metal dichalcogenide materials like MoTe2 and WTe2 have been predicted to host type-II WFs by DFT calculations and ARPES experiments. However, quantum oscillation experiments (QOE) disagree with the DFT calculations thus raising doubt about the existence of Weyl physics in these materials [1]. In order to address this discrepancy, we studied the role of electron interactions in Td-MoTe2 by employing DFT where the onsite Coulomb repulsion (Hubbard U) for the Mo 4d states is included within the DFT+U scheme. We found that in addition to explaining the QOE, inclusion of electron interaction is needed to explain the light-polarization dependence measured by ARPES [2]. We also found that while the number of Weyl points (WPs) and their position in the Brillouin Zone change as a function of U, a pair of such WPs very close to the Fermi level survive the inclusion of these important corrections. Our calculations suggest that the Fermi surface of Td-MoTe2 is in the vicinity of a correlations-induced Lifshitz transition which can be probed experimentally. If time allows, I will also present briefly our study of the interface between topological insulator and non-topological materials which are important for band engineering and studying emergent fundamental phenomena. References [1] D. Rhodes, R. Schonemann, N. Aryal, Q.R. Zhou et al., Bulk Fermi surface of the Weyl type-II semimetallic candidate ?-MoTe2, Phys. Rev. B 96, 165134 (2017). [2] N. Aryal and E. Manousakis, Importance of electron correlations in understanding the photo-electron spectroscopy and the Weyl character of MoTe2, Phys. Rev. B 99, 035123 (2019).

264. Environmental & Climate Sciences Department Seminar

"Simulating Mixed-Phase Clouds at High Latitudes: Model Evaluation, Improvement, and Interactions with Aerosol"

Presented by Xiahong Liu, Univ. Wyoming

Thursday, April 11, 2019, 11 am
Large Conference Room, Bldg. 490

Hosted by: Damao Zhang

Mixed-phase clouds are frequently observed in the Arctic and Antarctic and over the Southern Ocean, and have important impacts on the surface energy budget and regional climate. Global climate models (GCMs), an important tool for studying the climate change still have large biases in simulating the mixed-phase cloud properties, including supercooled liquid amount and liquid and ice phase partitioning. In this talk, I will present our recent works on mixed-phase clouds: (1) improving the representations of subgrid mixing and partitioning between cloud liquid and ice in mixed-phase clouds in the DOE's Energy Exascale Earth System Model (E3SM). Model simulations are evaluated against observation data obtained in the DOE Atmospheric Radiation Measurement (ARM) Program's field campaigns and long-term ground-based multi-sensor measurements; and (2) investigating the effects of aerosols, including dust and sea spray aerosol, on mixed-phase clouds. We found that dust, as ice nucleating particles (INPs), induces a global net warming via its indirect effect on mixed-phase clouds with a predominant warming in the NH midlatitudes and a cooling in the Arctic. INP sources of sea spray aerosol vary with time and geographic location with the maximum contribution in the marine boundary layer over the Southern Ocean, where dust has a limited influence. Modeled INP concentrations are compared with observations from different campaigns (e.g., MARCUS, SOCRATES, CAPRICORN).

265. Particle Physics Seminar

"The Search for the dark vector boson"

Presented by Diallo Boye, BNL

Wednesday, April 10, 2019, 4 pm
Small Seminar Room, Bldg. 510

Hosted by: Alessandro Tricolli

Hidden sector or dark sector states appear in many extensions to the Standard Model, to provide a particle candidate for dark matter in universe or to explain astrophysical observations such the as positron excess observed in the cosmic radiation flux. A hidden or dark sector can be introduced with an additional U(1)d dark gauge symmetry. The discovery of the Higgs boson during Run 1 of the Large Hadron Collider opens a new and rich experimental program based on the Higgs Portal. This discovery route uses couplings to the dark sector at the Higgs level, which were not experimentally accessible before. These searches use the possible exotic decays: H -> Z Zd -> 4l and H -> Zd Zd -> 4l. Here Zd is a dark vector boson. We have experience of this search from the Run 1 period of the LHC using the ATLAS detector at CERN. These results showed (tantalizingly) two signal events where none were expected, so that in the strict criteria of High Energy Physics, the result was not yet statistically significant. The Run 1 analysis for 8 TeV collision energy is further developed in Run 2 with 13 TeV collision energy, to expand the search area, take advantage of higher statistics, a higher Higgs production cross section, and substantially better performance of the ATLAS detector. The analysis is extended to search for heavier scalars decaying to dark vector bosons.

266. CFN Special Colloquium

"Discovering novel materials, and novel physics, with first-principles"

Presented by Nicola Marzari, École Polytechnique Fédérale de Lausanne (EPFL)

Wednesday, April 10, 2019, 3:30 pm
CFN, Bldg 735, 2nd Floor Seminar Room

Hosted by: Mark Hybertsen

First-principles simulations are one of the greatest accelerators in the world of science and technology. To provide some context, one could mention that 30,000 papers on density-functional theory are published every year; that 12 of these are in the top-100 most-cited papers in the entire history of science, engineering, and medicine; or that the doubling in capacity every 14 months has been the underwriter of computational science for the past 30 years. I'll highlight some of my own scientific, structural, and policy perspectives on this, taking as a case study the discovery of novel two-dimensional materials and of their properties and applications. I'll then argue how the need to calculate materials properties often forces a critical evaluation of some stalwarts of condensed-matter physics: in this case, learning that phonons are just a high-temperature approximation for heat carriers, or discovering that the Boltzmann transport equation can be generalized to describe simultaneously the propagation and interference of phonon wavepackets, thus unifying the description of thermal transport in crystals and glasses. Bio: Nicola Marzari holds the chair of Theory and Simulation of Materials at the École Polytechnique Fédérale de Lausanne, where he is also the director of the Swiss National Centre for Competence in Research MARVEL, on Computational Design and Discovery of Novel Materials (2014-26). Previous tenured appointment include the Toyota Chair for Materials Engineering at the Massachusetts Institute of Technology and the first Statutory (University) Chair of Materials Modelling at the University of Oxford, where he was also the director of the Materials Modelling Laboratory. He is the current chairman of the Psi-k Charity and Board of Trustees, and holder of an Excellence Chair at the University of Bremen.

267. BWIS Sponsored Event

"How Beauty Leads Physics Astray"

Presented by Sabine Hossenfelder, Frankfurt Institute for Advanced Studies, Germany

Tuesday, April 9, 2019, 5 pm
Large Seminar Room, Bldg. 510

Hosted by: Vivian Stojanoff

To develop fundamentally new laws of nature, theoretical physicists often rely on arguments from beauty. Simplicity and naturalness in particular have been strongly influential guides in the foundations of physics ever since the development of the standard model of particle physics. In this lecture I argue that arguments from beauty have led the field into a dead end and discuss what can be done about it.

268. Physics Colloquium

"Do Women Get Fewer Citations Than Men?"

Presented by Sabine Hossenfelder, Frankfurt Institute for Advanced Studies, Germany

Tuesday, April 9, 2019, 3:30 pm
Large Seminar Room, Bldg. 510

Hosted by: Berndt Mueller

I will talk about the results of a citation analysis on publication data from the arXiv and inspire in which we explored gender differences. I will further explain how we can use bibliometric analysis to improve the efficiency of knowledge discovery.

269. Condensed-Matter Physics & Materials Science Seminar

""Charge and lattice entanglement in quantum materials observed by TEM: Tb2Cu0.83Pd0.17O4 and Cu2S""

Presented by Wei Wang, Institute of Physics, Chinese Academy of Sciences, Beijing

Tuesday, April 9, 2019, 3 pm
Bldg. 480, Conference Room

Hosted by: Jing Tao

Plenty of physical properties in strongly electron correlated system are thought to arise from intricate interplay among charge, spin, orbital and lattice. Understanding the structural origin of these functionalities, such as superconductivity, multiferroics, etc, has attracted tremendous attention for decades. Using electron diffraction technique in TEM, we recently studied the modulated structure in Tb2Cu0.83Pd0.17O4 compound and phase transition in Cu2S. After a brief introduction of TEM techniques that I have employed for the study, I will report observations of electron-beam-induced smectic-nematic phase transitions in Tb2Cu0.83Pd0.17O4. Electron diffraction and HAADF-STEM images indicate a superlattice structure with Cu/Pd displacements perpendicular to the Cu-O plane on Cu sites. In addition, the superlattice modulation undergoes a reversible smectic-nematic phase transition under the electron beam illumination. Our in situ TEM results imply that the modulated structure root in a charge ordering at Cu sites. Then I will switch to an on-going study of the Cu2S at high temperature. Previous reports show that the crystal structural of Cu2S can be manipulated by electron beam illumination, suggesting a strong coupling between charge and lattice. To explore the structural phase transition and to have a better understanding of superionic behavior in this material, we focus on diffuse scattering in the electron diffraction patterns obtained at high temperatures, which results from short range ordering of Cu atoms. Electron diffraction tomographyic data were collected in order to reconstruct the real-space structure for Cu atoms. Preliminary results will be shown followed by a discussion with early-stage interpretations.

270. High Energy Theory Seminar

"Dark Matter — or What?"

Presented by Sabine Hossenfelder, Frankfurt Institute for Advanced Studies, Germany

Tuesday, April 9, 2019, 11 am
Small Seminar Room, Bldg. 510

Hosted by: Berndt Mueller

In this talk I will explain (a) what observations speak for the hypothesis of dark matter, (b) what observations speak for the hypothesis of modified gravity, and (c) why it is a mistake to insist that either hypothesis on its own must explain all the available data. The right explanation, I will argue, is instead a suitable combination of dark matter and modified gravity, which can be realized by the idea that dark matter has a super fluid phase.

271. NT / RIKEN seminar

"The Color Glass Condensate density matrix: Lindblad evolution, entanglement entropy and Wigner functional"

Presented by Alex Kovner, U Connecticut

Friday, April 5, 2019, 2 pm
Building 510, CFNS Seminar Room 2-38

Hosted by: Niklas Mueller

We introduce the notion of the Color Glass Condensate (CGC) density matrix ρ̂ . This generalizes the concept of probability density for the distribution of the color charges in the hadronic wave function and is consistent with understanding the CGC as an effective theory after integration of part of the hadronic degrees of freedom. We derive the evolution equations for the density matrix and show that it has the celebrated Kossakowsky-Lindblad form describing the non-unitary evolution of the density matrix of an open system. Additionally, we consider the dilute limit and demonstrate that, at large rapidity, the entanglement entropy of the density matrix grows linearly with rapidity according to dSe/dy=γ, where γ is the leading BFKL eigenvalue. We also discuss the evolution of ρ̂ in the saturated regime and relate it to the Levin-Tuchin law and find that the entropy again grows linearly with rapidity, but at a slower rate. Finally we introduce the Wigner functional derived from this density matrix and discuss how it can be used to determine the distribution of color currents, which may be instrumental in understanding dynamical features of QCD at high energy.

272. HET Lunch Discussion

"Quantum Simulation of Gauge Theories"

Presented by Taku Izubuchi, BNL HET

Friday, April 5, 2019, 12:15 pm
Building 510, Room 2-160

Hosted by: Aaron Meyer

273. Physics Colloquium

"Views and news on chiral transport"

Presented by Karl Landsteiner

Thursday, April 4, 2019, 4 pm
Large Seminar Room, Bldg. 510

Hosted by: Niklas Mueller

I present an effective action approach to chiral transport. Chiral Magnetic and Chiral Vortical Effect are treated in exact parallel and result in the known dependence on chemical potential and temperature. The approach sheds light on some of the more obscure features of chiral transport such as covariant and consistent anomalies and a seeming mismatch of the derivative expansion. As a related application I will comment on the thermal Hall effect on 2D topological insulators. Then I discuss a new example of chiral transport: anomalous Hall viscosity at the quantum critical point of the Weyl-semimetal/insulator transition. Results from a holographic model will be compared to a weak coupling quantum field theory analysis.

274. Particle Physics Seminar

"Flavour physics with dynamical chiral fermions"

Presented by Peter Boyle, University of Edinburgh

Thursday, April 4, 2019, 3 pm
Small Seminar Room, Bldg. 510

Hosted by: Hooman Davoudiasl

I discuss recent simulations with dynamical chiral fermions. In particular I focus on neutral kaon mixing amplitudes in and beyond the standard model, calculated for the first time with physical quark masses. A puzzle in the non-perturbative renormalisation of the BSM operators is resolved. The prospects for extension of this calculation to B-meson mixing amplitudes is discussed, and initial results for the standard model B mixing amplitudes presented. Prospects for future calculations over the next five years are considered.

275. Physics Colloquium

"Prospects on nucleon tomography"

Presented by Herve Moutard, Université Paris-Saclay

Wednesday, April 3, 2019, 3 pm
Large Seminar Room, Bldg. 510

Hosted by: Salvatore Fazio

Much attention has been devoted in recent years to the three-dimensional quark and gluon structure of the nucleon. In particular the concept of Generalized Parton Distributions promises an understanding of the generation of the charge, spin, and energy-momentum structure of the nucleon by its fundamental constituents. Forthcoming measurements with unprecedented accuracy at Jefferson Lab and at a future electron-ion collider will presumably challenge our quantitative description of the three-dimensional structure of hadrons. To fully exploit these future experimental data, new tools and models are currently being developed. After a brief reminder of what make Generalized Parton Distributions a unique tool to understand the nucleon structure, we will discuss the constraints provided by the existing measurements and review recent theoretical developments. We will explain why these developments naturally fit in a versatile software framework, named PARTONS, dedicated to the phenomenology and theory of GPDs.

276. HET Seminar

"Lattice QCD Inputs For Neutrino-Nucleon Scattering"

Presented by Raza Sufian, Jefferson Lab

Wednesday, April 3, 2019, 2:30 pm
Small Seminar Room, Bldg. 510

Hosted by: Aaron Meyer

We present lattice QCD calculation of nucleon axial and electromagnetic (up, down, strange and charm) form factors and discuss their impact on the understanding of neutrino-nucleon scattering. In a phenomenological study, using a combination of lattice QCD calculation of the strange-quark form factors, and MiniBooNE experimental neutrino scattering differential cross-section data in a limited kinematic regime, we obtain a precise determination of the weak axial form factor and of the corresponding neutral current weak-axial charge. We further show how a direct lattice QCD determination of neutral current weak-axial charge enable us to predict the BNL E734 data for the neutrino neutral current scattering differential cross section to high precision. We discuss how a direct lattice QCD calculation of neutrino-nucleon scattering cross sections can help to isolate nuclear effects in the neutrino-nucleus scattering.

277. Condensed-Matter Physics & Materials Science Seminar

"Topological semimetals predicted from first-principles and theoretical approaches"

Presented by Jiawei Ruan, School of Physics, Nanjing University, China

Monday, April 1, 2019, 11 am
Building 734, Seminar Room 201

Hosted by: Weiguo Yin

Weyl semimetals are new states of matter which feature novel Fermi arcs and exotic transport phenomena. Based on first-principles calculations, we report that the HgTe-class materials [1] as well as four chalcopyrites [2] are ideal Weyl semimetals, having largely separated Weyl points and uncovered Fermi arcs that are amenable to experimental detections. We also construct a minimal effective model to capture the low-energy physics of this class of Weyl semimetals. Our discovery is a major step toward a perfect playground of intriguing Weyl semimetals and potential applications for low-power and high-speed electronics. Besides the ideal Weyl semimetals, I will talk about Non-Hermitian nodal-line semimetals with an anomalous bulk-boundary correspondence [3]. I will also present recent results of saddle surface in topological materials and a new method to construct a simplified tight-binding model based on group theory analysis. [1] JR et al., Nature communications 7, 11136 (2016). [2] JR et al., PRL 116, 226801 (2016). [3] H. Wang, JR, and H. Zhang, PRB 99, 075130 (2019).

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