#### General Information

July 2015
Sunday Monday Tuesday Wednesday Thursday Friday Saturday

1

1. No events scheduled

2

1. 12:30 pm, Building 510 Room 2-160

Hosted by: Tomomi Ishikawa

3

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10

1. JUL

10

Friday

11 am, Bldg 911B, Large Conf. Rm., Rm. A202

Friday, July 10, 2015, 11:00 am

"Longitudinal space charge (LSC) effects are generally considered as detrimental in free-electron lasers as they can seed unwanted energy modulations and emittance growth. There has however been an increasing interest in devising accelerator beam lines capable of sustaining this LSC instability as a mechanism to operate as a coherent light source. In such a cascaded longitudinal space charge amplifier (LSCA), initial noise present in the beam density is amplified via the interplay of longitudinal space charge forces and properly located dispersive sections. To date most of these studies have been carried out with a one-dimensional impedance model for the LSC. We use an available grid-less three-dimensional N-body Barnes-Hut'' algorithm to simulate the 3D space charge force in the beam combined with ELEGANT and explore the limitations of the 1D model often used. We investigate, via numerical simulations, the performances of a cascaded LSCA beam line at the Fermilab's Advanced Superconducting Test Accelerator (ASTA)."

11

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23

1. JUL

23

Thursday

3 pm, Small Seminar Room, Bldg. 510

Thursday, July 23, 2015, 3:00 pm

Hosted by: Elizabeth Worcester

Beginning in 2011, the Double Chooz experiment has produced increasingly precise measurements of the neutrino oscillation parameter sin22θ13. These measurements rely on the detection of reactor antineutrinos through the inverse beta decay (IBD) interaction. The most recent analysis uses IBD interactions followed by neutron capture on hydrogen, rather than the standard Gd capture channel. A new artificial neural network-based signal selection, novel background rejection techniques, and reduced detection systematics make this analysis far more sensitive than the original H-channel measurement in Double Chooz. The precision of this new sin22θ13 measurement approaches that of the Gd-channel measurement, demonstrating the possibility of performing high-sensitivity physics measurements without a Gd dopant.

24

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29

1. JUL

29

Wednesday

2 pm, Small Seminar Room, Bldg. 510

Wednesday, July 29, 2015, 2:00 pm

Hosted by: Chien-Yi Chen

30

1. No events scheduled

31

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1. JUL

10

Friday

C-AD Accelerator Physics Seminar

""Cascaded Longitudinal Space Charge Amplifier for Short-Wavelength Radiation Generation at Fermilab's ASTA""

Presented by Aliaksei Halavanau, Northern Illinois University

11 am, Bldg 911B, Large Conf. Rm., Rm. A202

Friday, July 10, 2015, 11:00 am

"Longitudinal space charge (LSC) effects are generally considered as detrimental in free-electron lasers as they can seed unwanted energy modulations and emittance growth. There has however been an increasing interest in devising accelerator beam lines capable of sustaining this LSC instability as a mechanism to operate as a coherent light source. In such a cascaded longitudinal space charge amplifier (LSCA), initial noise present in the beam density is amplified via the interplay of longitudinal space charge forces and properly located dispersive sections. To date most of these studies have been carried out with a one-dimensional impedance model for the LSC. We use an available grid-less three-dimensional N-body Barnes-Hut'' algorithm to simulate the 3D space charge force in the beam combined with ELEGANT and explore the limitations of the 1D model often used. We investigate, via numerical simulations, the performances of a cascaded LSCA beam line at the Fermilab's Advanced Superconducting Test Accelerator (ASTA)."

2. JUL

23

Thursday

High Energy Physics Seminar

"New results from the hydrogen channel in Double Chooz"

Presented by Rachel Carr, Columbia University

3 pm, Small Seminar Room, Bldg. 510

Thursday, July 23, 2015, 3:00 pm

Hosted by: Elizabeth Worcester

Beginning in 2011, the Double Chooz experiment has produced increasingly precise measurements of the neutrino oscillation parameter sin22θ13. These measurements rely on the detection of reactor antineutrinos through the inverse beta decay (IBD) interaction. The most recent analysis uses IBD interactions followed by neutron capture on hydrogen, rather than the standard Gd capture channel. A new artificial neural network-based signal selection, novel background rejection techniques, and reduced detection systematics make this analysis far more sensitive than the original H-channel measurement in Double Chooz. The precision of this new sin22θ13 measurement approaches that of the Gd-channel measurement, demonstrating the possibility of performing high-sensitivity physics measurements without a Gd dopant.

3. JUL

29

Wednesday

HET/RIKEN Seminar

"Probing Charm-Yukawa at LHC, Status and Prospects"

Presented by Kohsaku Tobioka, Weizmann Institute/Tel Aviv University

2 pm, Small Seminar Room, Bldg. 510

Wednesday, July 29, 2015, 2:00 pm

Hosted by: Chien-Yi Chen

4. AUG

5

Wednesday

HET/RIKEN Seminar

"TBA"

Presented by Raffaele D'Agnolo, Institute for Advanced Study

2 pm, Small Seminar Room, Bldg. 510

Wednesday, August 5, 2015, 2:00 pm

Hosted by: Chien-Yi Chen

5. AUG

5

Wednesday

HET/RIKEN seminar

"TBA"

Presented by Raffaele D'Agnolo, Institute for Advanced Study

2 pm, Small Seminar Room, Bldg. 510

Wednesday, August 5, 2015, 2:00 pm

Hosted by: Chien-Yi Chen

6. AUG

12

Wednesday

HET/RIKEN Seminar

"Constraining Extended Higgs Sectors at the LHC and Beyond"

Presented by Tania Robens, Technical University of Dresden

2 pm, Small Seminar Room, Bldg. 510

Wednesday, August 12, 2015, 2:00 pm

Hosted by: Sally Dawson

7. SEP

8

Tuesday

Joint Nuclear Physics and Particle Physics Seminar

"Understanding the nature of neutrinos via neutrinoless double-beta decay"

Presented by Wenqin Xu, Los Alamos National Laboratory

11 am, Small Seminar Room, Bldg. 510

Tuesday, September 8, 2015, 11:00 am

Hosted by: Jin Huang

Neutrinos provide a critical portal to physics beyond the Standard Model, yet the nature of neutrinos is largely unknown, including the neutrino mass hierarcy and if neutrinos are Majorana particles. Majorana particles are fermions that are their own antiparticles. Neutrinos being Majorana particles would explicitly violate lepton number conservation, and would pave the way to understand the matter-antimatter asymmetry in the universe. Neutrinoless double-beta (0 ) decay is a hypothesized process where two neutrons decay into two protons and two electrons simultaneously without emitting neutrinos. It is possible only if neutrinos are Majorana particles, and it is the only feasible way to experimentally establish the Majorana or Dirac nature of neutrinos. The observation of 0 decay would also provide complementary information related to neutrino masses. After decades of experimental e orts, the next generation 0 decay experiments will have a signi cant discovery potential to observe 0 decay, if neutrinos are indeed Majorana particles. In this talk, we will discuss the physics of neutrinoless double beta decay and review the experiments searching for it. We will focus on the Majorana Demonstrator, a 40-kg modular Germanium detector array, which searches for 0 decay in 76Ge and aims at demonstrating a path forward to next generation 0 decay experiments.

8. OCT

1

Thursday

Particle Physics Seminar

"Top Quark Precision Physics and the Fate of the Universe"

Presented by Andreas Jung, Fermilab

3 pm, Small Seminar Room, Bldg. 510

Thursday, October 1, 2015, 3:00 pm

Hosted by: Ketevi A. Assamagan

The talk will discuss recent measurements in the top quark sector, the heaviest known elementary particle known so far, performed at the Fermilab Tevatron Collider and at the LHC. I will highlight Tevatron results that are competitive to those at the LHC, especially regarding the top quark mass and production asymmetry. The talk will also present CMS results on the top quark mass and Yukawa coupling. I will discuss the implications for the standard model electroweak sector regarding the vacuum stability. I will conclude with an outlook towards the high luminosity phase of the LHC and the CMS silicon detector upgrades required for the high luminosity phase.

9. OCT

15

Thursday

Particle Physics Seminar

"Recent Results from the BaBar Experiment"

Presented by David Norvil Brown, University of Louisville

3 pm, Small Seminar Room, Bldg. 510

Thursday, October 15, 2015, 3:00 pm

Hosted by: Ketevi A. Assamagan

TBD

1. RIKEN Lunch Seminar

"Short-distance matrix elements for D-meson mixing for 2+1 flavor lattice QCD"

Presented by Chia Cheng Chang, University of Illinois at Urbana-Champaign

Thursday, July 2, 2015, 12:30 pm
Building 510 Room 2-160

Hosted by: Tomomi Ishikawa

2. Nuclear Physics Seminar

"In search of old and new anomalous chiral effects in heavy ion collisions"

Presented by Jinfeng Liao, Indiana University

Tuesday, June 30, 2015, 11 am
Small Seminar Room, Bldg. 510

Hosted by: Oleg Eyser

The heavy ion collision provides a unique many-body environment where local domains of strongly interacting chiral medium may occur. Certain anomalous transport processes, forbidden in usual medium, become possible in such domains. These anomalous chiral effects have their microscopic origin at the fundamental quantum anomaly and manifest themselves macroscopically in hydrodynamic currents. In the first part of this talk we report our recent finding (arXiv:1504.03201) of a new gapless collective excitation, called the Chiral Vortical Wave (CVW) in a rotating quark-gluon plasma. The CVW wave equation will be derived, and we show that its solutions describe nontrivial CVW-induced charge transport. We further propose and estimate possible experimental signals. In the second part of this talk we report our state-of-the-art simulations of the long-sought-after Chiral Magnetic Effect (CME), performed in the anomalous hydrodynamic framework and taking into account identified background contributions (arXiV:1504.06906). We discuss the implications of our results for the experimental search of CME

3. Condensed-Matter Physics & Materials Science Seminar

"Microscopic engineering of complex oxide ground states"

Presented by Derek Meyers, University of Arkansas

Monday, June 29, 2015, 1:30 pm
ISB Bldg. 734, Conf. Rm. 201 (upstairs)

Hosted by: Mark Dean

Transition metal oxides have come to the forefront of condensed matter research in the past several decades due to their highly diverse phase space and remarkable susceptibility to external tuning. This has lead to their prevalence in the pursuit of designer phases, i.e. room temperature superconductivity, topological phases, and etc. In this talk we explore several methods for engineering the ground state of these systems including "ordered doping", applied epitaxial strain, and superlattice heterostructuring in an effort to gain further insight into the microscopic origin of this tunability. We employ synchrotron based x-ray spectroscopy and resonant diffraction to elucidate the explicit origin of the observed anomalous behaviors. In particular, our results reveal the ability to mask the effects of spin-orbit coupling in heavier oxides and to suppress or enhance bulk phase transitions by design.

4. Nuclear Theory/RIKEN Seminar

"Event by Event fluctuations in pQCD + saturation + hydro model: pinning down QCD matter shear viscosity in AA collisions"

Presented by Risto Paatelainen, University of Jyvaskyla

Friday, June 26, 2015, 2 pm
Small Seminar Room, Bldg. 510

Hosted by: Soeren Schlichting

We introduce an event-by-event perturbative-QCD + saturation + hydro ("EKRT") framework for ultrarelativistic heavy-ion collisions, where we compute the produced fluctuating QCD-matter energy densities from next-to-leading order perturbative QCD using a saturation conjecture to control soft particle production, and describe the space-time evolution of the QCD matter with dissipative fluid dynamics, event by event. We perform a simultaneous comparison of the centrality dependence of hadronic multiplicities, transverse momentum spectra, and flow coefficients of the azimuth-angle asymmetries, against the LHC and RHIC measurements. We compare also the computed event-by-event probability distributions of relative fluctuations of elliptic flow, and event-plane angle correlations, with the experimental data from Pb+Pb collisions at the LHC. We show how such a systematic multi-energy and multi-observable analysis tests the initial state calculation and the applicability region of hydrodynamics, and in particular how it constrains the temperature dependence of the shear viscosity-to-entropy ratio of QCD matter in its different phases in a remarkably consistent manner.

5. RIKEN Lunch Seminar

"One-Flavor QCD and the Dirac Spectrum at $\theta=0$"

Presented by Jacobus Verbaarschot, Stony Brook University

Thursday, June 25, 2015, 12:30 pm
Building 510 Room 2-160

Hosted by: Daniel Pitonyak

The chiral condensate of one-flavor QCD is continuous when the quark mass crosses zero. In the sector of fixed topological charge though, the chiral condensate becomes discontinuous at zero mass in the the thermodynamical limit. To reconcile these contradictory observations, we have evaluated the spectral density of the Dirac operator in the epsilon domain of one-flavor QCD. In this domain, we have obtained exact analytical expressions which show that the spectral density at $\theta = 0$ becomes a strongly oscillating function for negative quark mass with an amplitude that increases exponentially with the volume. As is the case for QCD at nonzero chemical potential, these strong oscillations invalidate the Banks-Casher formula and result in a chiral condensate that is continuous as a function of the quark mass. An additional subtlety is the effect of the topological zero modes which will be discussed as well.

6. Nuclear Theory/RIKEN seminar

"Jet angular broadening in Heavy-Ion collisions"

Presented by Yacine Mehtar-Tani, University of Washington

Friday, June 19, 2015, 2 pm
Small Seminar Room, Bldg. 510

Hosted by: Soeren Schlichting

The advent of the LHC opened up new perspectives for jet-quenching physics. For the first time, high enough energies are reached in heavy-ion experiments to produced jets in large numbers, and the unprecedented detector capabilities of ALICE, ATLAS and CMS, not only extend the kinematic range for the measurements previously performed at RHIC, but also allow to explore a variety of new jet-quenching observables. In this talk, I address the question of the angular broadening of jets in the presence of a dense QCD matter. I start by discussing the fundamental mechanisms underlying the formation of gluon cascades induced by multiple interactions of high energy jets with the quark-gluon plasma. Then, the rate equation that describes the evolution of the energy and angular distribution of the in-medium gluon shower is presented and solved. Two remarkable phenomena emerge. First and foremost the energy spectrum (of jet constituents) exhibits a scaling behavior characterized by a constant flow of energy towards low momenta akin to wave turbulence. As a result, energy is rapidly transported from the energy containing partons to low momentum gluons before it dissipates into the medium. Second, medium-induced gluon cascades develop and transport energy at parametrically large angles with respect to the jet axis. This picture is in semi-quantitive agreement with a recent CMS analysis of the missing energy in asymmetric dijet events where the energy balance is recovered at large angles and very soft particles.

7. PubSci

"Big Bang Physics and the Building Blocks of Matter"

Thursday, June 18, 2015, 7 pm
The Bahche 191 7th St, Brooklyn, NY 11215

Invite your friends and colleagues to a lively discussion for the science-interested (or just plain curious) and chat with scientists in an informal and friendly way. No stuffy lectures " just a dynamic talk with a diverse audience and a lot of good cheer. Physicists who work at Brookhaven's particle collider will talk about how they explore what happened at the dawn of time from a Lab on Long Island. How did the Universe take shape? What binds matter together? How do we answer those questions?

8. Particle Physics Seminar

"Detection of Lensing of the CMB by Dark Matter Halos"

Presented by Mathew S Madhavacheril, Stony Brook University

Thursday, June 18, 2015, 3 pm
Small Seminar Room, Bldg. 510

Hosted by: Morgan May

I will report on the first detection of lensing of the cosmic microwave background by dark matter halos. Halo lensing of the CMB provides a method for constraining cluster masses complementary to optical weak lensing, with the advantage that the source plane has a very well determined redshift and statistical properties. In this work, the lensing field was reconstructed from CMB temperature observations using the ACTPol telescope and stacked at the location of CMASS galaxies which trace dark matter halos of ~10^13 M_solar galaxy groups, providing a 3.2 sigma detection and a ~35% mass constraint. I will also briefly touch on the capabilities of future CMB experiments to use this method to constrain dark energy parameters.

9. RIKEN Lunch Seminar

"Self-similar evolution for inverse cascade of magnetic helicity driven by the chiral anomaly"

Presented by Yi Yin, Brookhaven National Laboratory

Thursday, June 18, 2015, 12:30 pm
Small Seminar Room, Bldg. 510

Hosted by: Daniel Pitonyak

We show by solving Maxwell's equations in the presence of chiral magnetic current that the chiral anomaly would induce the inverse cascade of magnetic helicity. We found at late time, the evolution of magnetic helicity spectrum is self-similar and axial charge decays as a power law in time. We visualize how a linked magnetic configuration would evolve into a knotted configuration in real space during such evolution.

10. HET/RIKEN Lunch Seminar

"Light Inflaton " hunting for it from CMB through the Dark Matter and down to the colliders"

Presented by Fedor Bezrukov, RBRC/U Conn

Friday, June 12, 2015, 12 pm
Building 510 Room 2-95

Hosted by: Amarjit Soni

11. Particle Physics Seminar

"Constraining the Standard Model and new physics with LHC data"

Presented by Alessandro Tricoli, CERN

Friday, June 12, 2015, 11 am
Small Seminar Room, Bldg. 510

Hosted by: Ketevi Assamagan

The Large Hadron Collider (LHC) project at CERN Laboratory in Geneva has achieved one of its primary goals, i.e. the discovery of the Higgs boson particle, which completes the Standard Model of particle physics. However, no signatures of new physics beyond the Standard Model have been observed yet, despite thorough searches. Nature turns out to be subtle. The direct search will continue in the upcoming LHC runs, however new physics can also be pursued indirectly by looking for deviations of experimental results from predictions in measurements of Standard Model processes. The LHC has provided a large data set during its first years of operations. This has been used to perform measurements of Standard Model processes that constrain predictions in the strong and electro-weak sectors and are sensitive to new physics in a model-independent way, thanks to the high level of precision and the extent of their kinematic reach. A good understanding of these processes is of paramount importance for precision Higgs physics, as well as for searches for new physics, as they constitute irreducible backgrounds. After presenting a selection of highlights of recent Standard Model measurements from the LHC, I will discuss how the precision and phase space reach of these measurements will improve in future LHC runs, given the increase of centre-of-mass energy and integrated luminosity, emphasising some of the experimental challenges ahead.

12. Particle Physics Seminar

"Search for dark sector particles at Belle and Belle II"

Presented by Igal Jaegle, University of Hawai`i at Mānoa

Thursday, June 11, 2015, 3 pm
Small Seminar Room, Bldg. 510

Hosted by: Ketevi A. Assamagan

The dark photon, A′,, and the dark Higgs boson, h′, are hypothetical constituents featured in a number of recently proposed Dark Sector Models. We will present a search for these particles in the so-called Higgs-strahlung channel, e+e''A′h′, with h′'A′A′. We investigated ten exclusive final-states with A′'e+e', μ+μ', or π+π', in the mass ranges 0.1 GeV/c2 <mA′<3.5 GeV/c2 and 0.2 GeV/c2 <mh′<10.5 GeV/c2. We also investigated three inclusive final-states, 2(e+e')X, 2(μ+μ')X, and (e+e')(μ+μ')X, where X denotes a dark photon candidate detected via missing mass, in the mass ranges 1.1 GeV/c2 <mA′<3.5 GeV/c2 and 2.2 GeV/c2 <mh′<10.5 GeV/c2. Using the entire 977fb'1 data set collected by Belle, we observed no significant signal. We will also discuss prospects for searches for light dark matter and the dark photon in the radiative decay process at Belle and Belle II.

13. HET/RIKEN seminar

"New physics in b—>s transitions after LHC run 1"

Presented by Wolfgang Altmannshofer, Perimeter Institute

Wednesday, June 10, 2015, 2 pm
Small Seminar Room, Bldg. 510

Hosted by: Chien-Yi Chen

I will discuss interpretations of the recent updated angular analysis of the B->K*mu+mu- decay by the LHCb collaboration. A global fit to all relevant measurements probing the flavor changing neutral current b->s mu mu transition shows tensions with Standard Model expectations. Assuming hadronic uncertainties are estimated in a sufficiently conservative way, I will discuss the implications of the experimental results on new physics, both model independently as well as in the context of models with flavor changing Z' bosons.

14. Nuclear Theory/RIKEN seminar

"Novel mechanisms of charmonium suppression/enhancement in pA and AA collisions"

Presented by Boris Kopeliovich, Universidad Tecnica Federico Santa Maria, Valparaiso

Friday, June 5, 2015, 2 pm
Small Seminar Room, Bldg. 510

Hosted by: Soeren Schlichting

Charmonium production in pA collisions is known to be suppressed by shadowing and absorption. There are however nuclear effects, which enhance charmonium yield. They steeply rise with energy and seem to show up in LHC data for J/psi production in pA collisions. In the case of heavy ion collisions produced charmonia are additionally suppressed by final state interaction in the created dense medium. On the contrary to current evaluations of the melting effects caused by Debye screening, a charmonium produced with a large pT easily survives even at high temperatures. Another source of charmonium suppression, missed in previous calculations, color-exchange interactions with the medium, leads to suppression of a comparable magnitude. A quantitative comparison is performed.

15. Condensed-Matter Physics & Materials Science Seminar

"GGE and applications for integrable models"

Presented by Garry Goldstein, Rutgers University

Thursday, June 4, 2015, 4 pm
ISB 2nd floor seminar room

Hosted by: Robert Konik

We consider quenches of integrable models. We derive a Yudson representation applicable to finite sized systems. Using this representation we find expressions for the time dependence of density density and related correlation functions for an arbitrary quench of the repulsive LiebLiniger gas. We use this to show that the GGE formalism is applicable to the long time limit for quenches of the Lieb-Liniger gas with sufficiently regular initial states. We then show that no similar GGE formalism applies to quenches for integrable models with bound states (such as the XXZ model or the Hubbard model). We study several specific examples of quenches, in particular quenches where the initial state is a Mott insulator or has low entropy. We find the exact quasiparticle density for such quenches and use it to study the long time limit of some correlation functions for the system. We also consider quenches of confined systems, in particular the Lieb-linger gas in a box. We show that the GGE formalism applies to the long time average of such quenches. We use this observation to compute the long time average quasiparticle density for some quenches similar to the Quantum Newton's cradle quench experiment. We also compute various correlation functions for the system in particular the probability distribution for the particle velocity.

16. Condensed-Matter Physics & Materials Science Seminar

"Band edge and photo induced superconductivity"

Presented by Garry Goldstein, Rutgers

Thursday, June 4, 2015, 1:30 pm
2nd Fl Lecture Room ISB

Hosted by: Robert Konik

We discuss novel routes to obtain superconductivity in semiconductors. We consider a semiconductor with a band dispersion where there is a band edge, such as semiconductors with Rashba spin-orbit coupling or bilayer graphene with a voltage between the layers. We find robust superconductivity, both p-wave and s-wave depending on the type of band edge, for semiconductors with attractive interactions (such as those caused by phonon exchange) when we tune the chemical potential close to the band edge. We also consider photo induced superconductivity in a two band semiconductor. We use optical pumping to induce nonequilibrium populations within the bands. We find robust superconductivity for appropriate chemical potential and dispersion relations for the bands. This s-wave superconductivity can be induced by both repulsive and attractive interactions depending on the exact band dispersions. Various band geometries are discussed.

17. RIKEN Lunch Seminar

"Non-relativistic particles in a thermal bath"

Presented by Antonio Vairo, Munich Technical University

Thursday, June 4, 2015, 12:30 pm
Building 510 Room 2-160

Hosted by: Tomomi Ishikawa

18. HET/RIKEN Seminar

"Cascade Decays of a Leptophobic Boson"

Presented by Bogdan Dobrescu, Fermilab

Wednesday, June 3, 2015, 2 pm
Small Seminar Room, Bldg. 510

Hosted by: Chien-Yi Chen

19. Physics Colloquium

"Quarkonium with Effective field theories"

Presented by Nora Brambilla, Munich Technical University

Tuesday, June 2, 2015, 3:30 pm
Large Seminar Room, Bldg. 510

Hosted by: Peter Petreczky

Quantum Chromodynamics (QCD) is the sector of the Standard Model of particle physics that describes the strong interaction, deceptively simple to formulate but notoriously difficult to solve. Heavy quarkonium is a multiscale system that probes the different energy regimes of QCD, from the high-energy region, where an expansion in the coupling constant is possible and precision studies may be done, to the low-energy region, dominated by confinement and the many manifestations of the nonperturbative strong dynamics. Properties of production and absorption of quarkonium in a medium are also crucial for the study of QCD at high density and temperature. On the theoretical side, the construction of new nonrelativistic effective field theories for quarkonium has recently revolutionized the field providing both a conceptual framework and a powerful calculational tool. On the experimental side, the diversity, quantity and accuracy of the data collected in the last few years at B and tau-charm factories and at RHIC and LHC experiments is impressive, featuring the observation of new states and new unexpected processes. I will discuss these theoretical and experimental advancements and their implications for our understanding of strong interactions.

20. Nuclear Physics Seminar

"Elliptic flow from anisotropic escape"

Presented by Denes Molnar, Purdue University

Tuesday, June 2, 2015, 11 am
Small Seminar Room, Bldg. 510

Hosted by: Jin Huang

While hydrodynamics is regarded as the dominant paradigm for describing heavy-ion collisions at RHIC and LHC energies, its applicability to nuclear reactions is not very well understood. Open question remain about the mechanism of rapid thermalization, initial conditions, treatment of decoupling (conversion of the fluid to particles), finite system effects, and quantum corrections in very small systems, for example. In a recent work (arXiv:1502.05572) we showed that in the AMPT transport model elliptic flow is generated quite differently from hydrodynamics, mainly through anisotropic escape from the collision zone. I will demonstrate that this is, in fact, a general feature of kinetic theory, originating in the modest opacities <Ncoll> \sim 4-5 in AMPT calculations. Implications of the escape effect will be discussed together with connections to other hydro related problems such as proper particle distributions (arXiv:1404.8750) and anisotropic flow from quantum mechanics (arXiv:1404.4119).

21. Particle Physics Seminar

"LHCb Run I Results and Run II Prospects"

Presented by Philip Ilten, Massachusetts Institute of Technology

Thursday, May 28, 2015, 3 pm
Small Seminar Room, Bldg. 510

Hosted by: Ketevi A. Assamagan

The LHCb detector is a forward arm spectrometer on the Large Hadron Collider, designed for the study of particles containing b or c quarks. A variety of recent results from the Run I dataset, taken from 2010 - 2013, will be presented, emphasizing the scope of the LHCb physics program. These areas include central exlusive production of quarkonia, exotic particle searches, precision electroweak cross-sections, CKM measurements, and more. Prospects for Run II measurements will be outlined.

22. Condensed-Matter Physics & Materials Science Seminar

"Transport properties of novel thermoelectric materials"

Presented by Hang Chi, Department of Physics, University of Michigan

Thursday, May 28, 2015, 11 am
Bldg.480 Conf. Rm

Hosted by: Qiang Li

Thermoelectric materials can recover waste industrial heat and convert it to electricity as well as provide efficient local cooling of electronic devices. The efficiency (determined by the dimensionless figure-of-merit ZT) of such environmentally responsible and exceptionally reliable solid state energy conversion can be enhanced through (i) electronic band engineering (n-type Mg2Si-Mg2Sn solid solutions and p-type SnTe) and (ii) thermal conductivity reduction (Ge/Te double substituted CoSb3). Detailed transport and structure studies of Bi2Te3-based single crystals demonstrate that a bulk (semi-)insulating state for such a topological insulator can be achieved via group III (Tl or In) elemental doping, which opens an avenue for further investigations of transport phenomena related to surface states. Further systematic study in Bi2Te3-based molecular beam epitaxial (MBE) thin films grown on sapphire (0001) and/or BaF2 (111) substrates, reveal that the peak of phonon drag can be tuned by the choice of substrates with different Debye temperatures.

23. Brookhaven Lecture

"505th Brookhaven Lecture: 'Scanning the Structure of Steel From Nuclear Reactor Vessels'"

Presented by Lynne Ecker, Nuclear Science & Technology Department

Wednesday, May 27, 2015, 4 pm
Berkner Hall Auditorium

Hosted by: Thomas Watson

24. Nuclear Physics Seminar

"Probing Nucleon Structure Through Transversely Polarized Proton-proton Collisions at STAR"

Presented by Jim L. Drachenberg, Valparaiso University

Tuesday, May 26, 2015, 11 am
Small Seminar Room, Bldg. 510

Hosted by: Oleg Eyser

At leading twist, a complete picture of the one-dimensional momentum structure of the nucleon requires knowledge of three types of parton distribution functions (PDFs): the unpolarized PDFs; the helicity PDFs; and the transversity PDF, related to the transverse polarization of quarks within a transversely polarized nucleon. Current global extractions of transversity are limited by the kinematic reach of existing semi-inclusive deep-inelastic scattering (SIDIS) experiments. Beyond the open questions of one-dimensional nucleon structure, myriad opportunities abound in exploring the multi-dimensional structure of the nucleon. A step toward this goal is to investigate the nature of the transverse momentum dependence (TMD) of nucleon parton densities and their relation to nucleon spin polarization. The STAR experiment at RHIC proposes to investigate these and other spin-related phenomena through the interaction of high-energy collisions between spin-polarized protons. In preliminary results from data collected in 2011 at $\sqrt{s}=500$ GeV and in 2012 at $\sqrt{s}=200$ GeV, STAR has observed the first non-zero spin asymmetries due to the effects of transversity in proton-proton collisions. Studying these effects through both jet+hadron and di-hadron production channels and across a range of collision energy yields the potential not only to extend understanding of transversity beyond the current kinematic reach but also to address longstanding theoretical questions concerning the universality and evolution of transversity and polarized fragmentation functions. From the 2011 dataset STAR has also released the first preliminary measurements sensitive to the Sivers TMD PDF in weak-boson production. Weak boson production provides an ideal tool for isolating the unconstrained sea-quark Sivers PDF and may provide sensitivity to the expected modified universality of the Sivers PDF when compared to SIDIS. These exploratory measurements pave the way for future higher precision inv

25. RIKEN Lunch Seminar

"Dysonian dynamics of the Ginibre ensemble"

Presented by Piotr Warchol, Jagiellonian University

Thursday, May 21, 2015, 12:30 pm
Building 510 Room 2-160

Hosted by: Tomomi Ishikawa

I will present a study of the time evolution of Ginibre matrices whose elements undergo Brownian motion. The non-Hermitian character of the Ginibre ensemble binds the dynamics of eigenvalues to the evolution of eigenvectors in a non-trivial way, leading to a system of coupled nonlinear equations resembling those for turbulent systems. We will formulate a mathematical framework allowing simultaneous description of the flow of eigenvalues and eigenvectors, and unravel a hidden dynamics as a function of new complex variable, which in the standard description is treated as a regulator only. We shall solve the evolution equations for large matrices and demonstrate that the non-analytic behavior of the Green's functions is associated with a shock wave stemming from a Burgers-like equation describing correlations of eigenvectors. I will start by reviewing similar notions in a simpler, Hermitian setting. Joint work with Zdzislaw Burda, Jacek Grela, Maciej A. Nowak and Wojtek Tarnowski (Phys.Rev.Lett. 113 (2014) 104102).

26. Nuclear Physics Seminar

"Low pT photon production at confinement: The missing piece to the direct photon puzzle"

Presented by Dr. Sarah Campbell, Columbia University

Tuesday, May 19, 2015, 11 am
Small Seminar Room, Bldg. 510

Hosted by: Jin Huang

Low pT direct photons in Au+Au collisions are produced in excess of the TAA-scaled p+p yields and with a large azimuthal anisotropy, v2. This talk considers that these low pT direct photons are produced by radially boosted quarks undergoing soft-gluon mediated quark-anti-quark interactions as the system becomes color-neutral. A Monte Carlo simulation of direct photons and Chi-squared comparisons of the published PHENIX direct photon and identified particle v2 data are used to test this description. The Monte Carlo simulation reproduces the shape of the direct photon pT excess and the resulting direct photon v2 agrees, despite being systematically low, with the published 0-20% and 20-40% Au+Au low pT direct photon v2 in both centralities. Comparisons to recent preliminary direct photon results will also be shown.

27. Nuclear Theory/RIKEN seminar

"Off-shell amplitudes and their applications"

Presented by Piotr Kotko, Pennsylvania State University

Friday, May 15, 2015, 2 pm
Small Seminar Room, Bldg. 510

Hosted by: Soeren Schlichting

28. C-AD Accelerator Physics Seminar

"A Robinson Wiggler for Lifetime and Brilliant Improvement at the Metrology Light Source"

Presented by Tobias Goetsch, Helmholtz-Zentrum, Germany

Thursday, May 14, 2015, 4 pm
Large Conf. Rm. Bldg. 911B, Rm. A202

Hosted by: Wolfram Fischer

"The beam lifetime in electron storage rings concerns machines running in decay mode as well as machines doing top-up. A standard procedure to increase the lifetime is via bunch lengthening as the lifetime depends on the electron density in the bunch. Bunch lengthening is typically achieved with higher harmonic (Landau) cavities. There are several advantages in using a different approach: it is possible to increase the bunch length by installing a transverse gradient (Robinson) Wiggler, which allows to transfer damping between the horizontal and the longitudinal plane. While increasing the bunch length, the horizontal emittance is being reduced yielding advantages regarding the source size depending on the magnet optics. At the Metrology Light Source, a primary source standard used by Germanys national metrology institute (Physikalisch-Technische Bundesanstalt), such a scheme is being investigated. The prospects are higher brilliance for the important beamlines together with a lifetime improvement in the order of 100 %."

29. Particle Physics Seminar

"Dark matter search results from the PandaX-I experiment"

Presented by Mengjiao Xiao, Shanghai Jiao Tong University

Thursday, May 14, 2015, 3 pm
Small Seminar Room, Bldg. 510

Hosted by: Elizabeth Worcester

The dark matter is a leading candidate to explain gravitational effects observed in galactic rotational curves, galaxy clusters, and the large scale structure formation, etc. The nature of dark matter is one of the most fundamental problems in physics. Proposals of dark matter candidates usually involve new physics and new particles. Among the various candidates, one compelling class of particles are WIMPs (Weakly Interacting Massive Particles). WIMPs are being studied in colliders, indirect and direct detection experiments. In recent years, new techniques in WIMP direct detection using noble liquids (xenon, argon) have shown exceptional potential due to the capability of background suppression and discrimination, and scalability to large target masses. PandaX is a low threshold dual-phase xenon dark matter experiment operating at the China Jin-Ping Underground Laboratory (CJPL). The PandaX detector is staged. We released the first dark matter search data for PandaX-I on August 2014. In this talk, I will give an introduction to the PandaX-I detector, and then followed by the details of the physics analysis as well as the latest results.

30. RIKEN Lunch Seminar

"Geometrical scaling - a window to saturation"

Presented by Michal Praszalowicz, Jagiellonian University

Thursday, May 14, 2015, 12:30 pm
Building 510 Room 2-160

Hosted by: Daniel Pitonyak

Geometrical is a consequence of a traveling wave solution of the non-linear QCD evolution equation, so called Balitski-Kovchegov equation. We shall demonstrate the existence of GS in various high energy reactions. Among different consequences of GS there is a linear rise of charged particle multiplicity (Nch) and mean transverse momentum (pT) with scattering energy. Furthermore, a correlation of meant pT and Nch is predicted to scale in a way that depends on the the way particles are produced from the volume excited in a hadron-hadron scattering. This is mostly visible in heavy ion collisions at different centralities.

31. HET/RIKEN seminar

"Colorless Top Partners and Naturalness"

Presented by Gustavo Burdman, IAS/University of São Paulo

Wednesday, May 13, 2015, 2 pm
Small Seminar Room, Bldg. 510

Hosted by: CheinYi Chen

32. Physics Colloquium

"Where Did Half the Starlight in the Universe Go"

Presented by Mark Devlin, University of Pennsylvania

Tuesday, May 12, 2015, 3:30 pm
Large Seminar Room, Bldg. 510

Hosted by: Peter Yamin

We believe that approximately half of all the light from stars is absorbed and reprocessed by dust. The resulting emission is grey body with a temperature near 30 Kelvin. The COBE satellite made the first measurements of the resulting Far Infrared Background (FIRB), but since that time, we have been unable to resolve the background into individual galaxies. The Balloon-borne Large Aperture Submillimeter Telescope (BLAST) was designed to do this job. Its three bands at 250, 350, and 500 microns span the peak in emission for galaxies at z=1. I will discuss the BLAST experiment and present results from our measurements of resolved and unresolved galaxies. I will also discuss the implications for star formation in our own galaxy and how dust is changing the way we look at current and future searches for primordial gravity waves with the Cosmic Microwave Background.

33. Nuclear Theory/RIKEN Seminar

"Solving the NLO BK equation in coordinate space"

Presented by Tuomas Lappi, University of Jyvaskyla

Friday, May 8, 2015, 2 pm
Small Seminar Room, Bldg. 510

Hosted by: Soeren Schlichting

We present results from a numerical solution of the next-to-leading order (NLO) Balitsky-Kovchegov (BK) equation in coordinate space in the large Nc limit. We show that the solution is not stable for initial conditions that are close to those used in phenomenological applications of the leading order equation. We identify the problematic terms in the NLO kernel as being related to large logarithms of a small parent dipole size, and also show that rewriting the equation in terms of the "conformal dipole" does not remove the problem. Our results qualitatively agree with expectations based on the behavior of the linear BFKL equation.

34. HET / Riken Lunch Seminar

"Stealth Composite Dark Matter"

Presented by Ethan Neil, RBRC/Colorado

Friday, May 8, 2015, 12 pm
Building 510 Room 2-95

Hosted by: Amarjit Soni

35. RIKEN Lunch Talk

"NLO transverse momentum broadening and QCD evolution of qhat"

Presented by Hongxi Xing, Los Alamos National Lab

Thursday, May 7, 2015, 12:30 pm
Building 510 Room 2-160

Hosted by: Daniel Pitonyak

36. Nuclear Theory/RIKEN Seminar

"Applications of Soft-Collinear Effective theory to hadronic and nuclear collisions"

Presented by Ivan Vitev, Los Alamos National Laboratory

Friday, May 1, 2015, 2 pm
Small Seminar Room, Bldg. 510

Hosted by: Soeren Schlichting

Effective field theory (EFT) is a powerful framework based on exploiting symmetries and controlled expansions for problems with a natural separation of energy or distance scales. EFTs are particularly important in QCD and nuclear physics. An effective theory of QCD, ideally suited to jet applications, is Soft-Collinear Effective Theory (SCET). Recently, first steps were taken to extend SCET and describe jet evolution in strongly-interacting matter. In this talk I will demonstrate that the newly constructed theory, called SCETG, allows us to go beyond the traditional energy loss approximation in heavy ion collisions and unify the treatment of vacuum and medium-induced parton showers. It provides quantitative control over the uncertainties associated with the implementation of the in-medim modification of hadron production cross sections and allows us to accurately constrain the coupling between the jet and the medium. I will further show how SCET and SCETG can be implemented to evaluate reconstructed jet observables, such as jet shapes.

37. HET/RIKEN seminar

"Higgs as a Lamp Post of New Physics"

Presented by JiJi Fan, Syracuse

Wednesday, April 29, 2015, 2 pm
Small Seminar Room, Bldg. 510

Hosted by: Chien-Yi Chen

38. Nuclear Theory/RIKEN seminar

"Heavy Hadrons under Extreme Conditions"

Presented by Laura Tolos, Instituto de Ciencias del Espacio (IEEC-CSIC)

Friday, April 24, 2015, 2 pm
Small Seminar Room, Bldg. 510

Hosted by: Soeren Schlichting

Hadrons under extreme conditions of density and temperature have captured the interest of particle and nuclear physicists as well as astrophysicists over the years in connection with an extensive variety of physical phenomena in the laboratory as well as in the interior of stellar objects, such as neutron stars. One of the physics goals is to understand the origin of hadron masses in the context of the spontaneous breaking of the chiral symmetry of Quantum Chromodynamics (QCD) at low energies in the non-perturbative regime and to analyze the change of the hadron masses due to partial restoration of this symmetry under extreme conditions. Lately other proper QCD symmetries have also become a matter of high interest, such as heavy-quark flavor and spin symmetries. These symmetries appear when the quark masses become larger than the typical confinement scale and they are crucial for characterizing hadrons with heavy degrees of freedom. In this talk I will address the properties of heavy hadrons under extreme conditions based on effective theories that incorporate the most appropriate scales and symmetries of QCD in each case. With the on-going and upcoming research facilities, the aim is to move from the light-quark to the heavy-quark sector and to face new challenges where heavy hadrons and new QCD symmetries will play a dominant role.

39. Biological, Environmental, & Climate Sciences (BECS) Department Seminar

"High-resolution CAM5 simulations of varying complexity"

Presented by Kevin Reed, Stony Brook University

Friday, April 24, 2015, 10 am
Conference Room, Bldg 815E

Hosted by: Ernie Lewis

In our continued effort to understand the climate system and improve its representation in general circulation models (GCMs) it is crucial to develop new methods to evaluate these models. This is certainly true as the GCM community advances towards high horizontal resolutions (i.e., grid spacing less than 50 km), which will require interpreting and improving the performance of many model components. Idealized, or reduced complexity, frameworks can be used to investigate how model assumptions impact behavior across scales. This work makes use of a range of National Center for Atmospheric Research and Department of Energy Community Atmosphere Model version 5 (CAM5) simulations, ranging from simplified global radiative-convective equilibrium (RCE) simulations to full decadal simulations of present-day and future climate. The various CAM5 configurations provide useful insights into the model's ability to simulate extreme precipitation events and tropical cyclones. Furthermore, the impact of horizontal resolution and the choice of CAM5 dynamical core on the simulation of extreme events will be explored. Finally, time slice experiments using the Representative Concentration Pathway (RCP) 8.5 scenario for greenhouse gas concentrations are assessed and compared to present-day simulations. Overall, this work is part of a continued effort to understand how weather extremes may vary in a changing climate using next-generation high-resolution climate models.

40. Particle Physics Seminar

"(Real) Early Universe Cosmology with Quark Gluon Plasma"

Presented by Niayesh Afshordi, Perimeter Institute for Theoretical Physics

Thursday, April 23, 2015, 3 pm
Small Seminar Room, Bldg. 510

Hosted by: Morgan May

An intriguing possibility that can address pathologies in both early universe cosmology (i.e. the horizon problem) and quantum gravity (i.e. non-renormalizability), is that particles at very high energies and/or temperatures could propagate arbitrarily fast. In this talk, I introduce Thermal Tachyacoustic Cosmology (TTC), i.e. this scenario with thermal initial conditions. We find that a phase transition in the early universe, around the scale of Grand Unified Theories (GUT scale; T∼10^{15} GeV), during which the speed of sound drops by several orders of magnitude within a Hubble time, can fit current CMB observations. However, I will then argue that cosmological bounds on the density of primordial black holes suggest that Lorentz invariance in the primordial thermal plasma may not recover until much lower temperatures, close to the QCD phase transition. This presents the exciting possibility of testing this scenario in the thermal plasma produced in relativistic heavy ion collisions.

41. Particle Physics Seminar

"Implications of Cosmological Observations for History of Early Universe"

Presented by Ghazal Geshnizjani, University of Waterloo/ Perimeter Institute for Theoretical Physics

Wednesday, April 22, 2015, 3 pm
Building 510 Room 2-160

Hosted by: Morgan May

I will argue that any theory of early universe that matches cosmological observations should include a phase of accelerated expansion (i.e. inflation) or it has to break at least one of the following tenets of classical general relativity: Null Energy Conditions (NEC), sub-luminal signal propagation, or sub-Planckian energy densities. This proof extends to a large class of theories with higher (spatial) derivative or non-local terms in the action as well. Interestingly, only theories in the neighbourhood of Lifshitz points with ω ∝ k^0 and k^3 are excluded from the proof. I will also discuss in what sense detecting primordial gravitational waves is a smoking gun for inflation.

42. Condensed-Matter Physics & Materials Science Seminar

"Establishing an Atomistic Picture of Gas Adsorption in Metal Organic Frameworks"

Presented by Anna Plonka, SUNY-Stony Brook, Poland

Wednesday, April 22, 2015, 1:30 pm
ISB Bldg. 734, Conf. Rm. 201 (upstairs)

Hosted by: Simon Billinge/Emil Bozin

Selective adsorption and sequestration of carbon dioxide from sources of anthropogenic emissions is important to mitigate the growing level of the atmospheric CO2. Solid state adsorbents, such as metal organic frameworks (MOFs), are proposed as an alternative to the currently used toxic and corrosive alkanolamine solutions. Experimental gas sorption studies of MOFs usually focus on gas isotherms measurements that, while providing the necessary information on the overall gas uptake and framework behavior upon gas loading, yield limited information on the mechanism of the gas adsorption. Molecular level understanding of gas adsorption in MOFs is an important problem and the most detailed structural models necessary to elucidate the adsorbate-adsorbent interaction can be obtained with the crystallographic techniques. This talk will present the recent exciting discoveries of CO2 and hydrocarbon adsorption in MOFs. In contrast to current trends in the design of MOFs, we discovered the unique mechanism responsible for a high CO2/N2 adsorption selectivity in a Ca-based MOF: Ca(sdb), (sdb: 4,4'-sulfonyldibenzoate), even in the presence of water in the gas stream. Single crystal XRD (SCXRD) experiments of gas loaded samples revealed that the v-shaped linker provides a "pi-pocket" formed by two phenyl rings, and that CO2 locate between the rings, resulting in a high heat of adsorption. To determine the gas adsorption performance in situ in the presence of water, we used differential scanning calorimetry technique (XRD-DSC) that allows for measuring enthalpy while collecting X-ray diffraction patterns, to evaluate the structural response during the gas adsorption. The XRD-DSC technique and single crystal diffraction were further used to evaluate the CO2 adsorption in a Cd-analog of Ca(sdb), hydrocarbon adsorption in two Ca-based MOFs and gate opening mechanism in a Mn-based MOF. The knowledge acquired can promote the directed synthetic search for novel

43. Physics Colloquium

"Neutrinos and friends in the past and present universe"

Presented by Alex Kusenko, UCLA

Tuesday, April 21, 2015, 3:30 pm
Large Seminar Room, Bldg. 510

Hosted by: Morgan May

Neutrinos play a role in various aspects of cosmology, including production of light elements, and the rate of expansion of the universe. Furthermore, the neutrino masses imply the likely existence of right-handed neutrinos, which can exist in the form of dark matter, and which can explain the matterantimatter asymmetry of the universe. I will discuss the many faces ordinary and hypothetical neutrinos in cosmology.

44. Center for Data-Driven Discovery C3D

"Computing Intensive Problems in Cosmology"

Presented by Anze Slosar

Tuesday, April 21, 2015, 2 pm
John Dunn Seminar Room, Bldg. 463

Hosted by: Robert Harrison

Cosmology is a branch of physics that studies the whole universe as a single physical system. Computing intensive methods are used throughout, both for data analysis and for theoretical modeling. The computational difficulties are in most cases due to existence of gravitational force which is important at all scales. This makes problems fundamentally different from problems in particle physics where each collision event can be considered to be statistically independent. In simulations, it is necessary to take into account the force contribution of any particle to any other and in data analysis the correlations between any two measurements. I will overview problems, solutions and current limitations. Time permitting, I will describe more technical aspects of the code we are developing to analyze data from the spectroscopic datasets.

45. Condensed-Matter Physics & Materials Science Seminar

"Competing Superexchange Interactions in Double Perovskite Osmates"

Presented by Ryan Morrow, Ohio State University

Monday, April 20, 2015, 1:30 pm
ISB Bldg. 734, Conf. Rm. 201 (upstairs)

Hosted by: Simon Billinge/Emil Bozin

Double perovskites, A2BB'O6, containing mixed transition metal ions have exhibited numerous desirable properties such as colossal magnetoresistance, half metallic transport, and high temperature ferrimagnetism. However, a predictive understanding of the superexchange mechanisms which control the magnetism of these materials when they are insulating and B is 3d transition metal and B' is a 4d or 5d transition metal has remained elusive. In this work, a number of insulating double perovskite osmates, A2BOsO6 (A=Sr,Ca,La; B=Cr,Fe,Co,Ni) have been chosen and studied using magnetometry, specific heat, XMCD, and neutron powder diffraction techniques in order to systematically probe the effects of electronic configuration and bonding geometry on the magnetic ground state. It is concluded that the magnetic properties of these materials are controlled by a competition between short range B��'O��'Os and long range superexchange interactions which are sensitive to bonding geometry resulting in tunability of the magnetic ground state.

46. Nuclear Physics & RIKEN Theory Seminar

"Consistency of Perfect Fluidity and Jet Quenching in semi-Quark-Gluon Monopole Plasmas"

Presented by Jiechen Xu, Columbia University

Friday, April 17, 2015, 2 pm
Small Seminar Room, Bldg. 510

Hosted by: Soeren Schlichting

Abstract: We utilize a new framework, CUJET3.0, to deduce the energy and temperature dependence of jet transport parameter, q^(E>10GeV,T), from a combined analysis of available data on nuclear modification factor and azimuthal asymmetries from RHIC/BNL and LHC/CERN on high energy nuclear collisions. Extending a previous perturbative-QCD based jet energy loss model (known as CUJET2.0) with (2+1)D viscous hydrodynamic bulk evolution, this new framework includes three novel features of nonperturbative physics origin: (1) the Polyakov loop suppression of color-electric scattering (aka "semi-QGP" of Pisarski et al) and (2) the enhancement of jet scattering due to emergent magnetic monopoles near Tc (aka "magnetic scenario" of Liao and Shuryak) and (3) thermodynamic properties constrained by lattice QCD data. CUJET3.0 reduces to v2.0 at high temperatures T>400 MeV, but greatly enhances q^ near the QCD deconfinement transition temperature range. This enhancement accounts well for the observed elliptic harmonics of jets with pT>10 GeV. Extrapolating our data-constrained q^ down to thermal energy scales, E∼2 GeV, we find for the first time a remarkable consistency between high energy jet quenching and bulk perfect fluidity with η/s∼T3/q^∼0.1 near Tc.

47. Particle Physics Seminar

"Cosmology with Strong Gravitational Lenses"

Presented by Phil Marshall, SLAC National Accelerator Laboratory

Thursday, April 16, 2015, 3 pm
Small Seminar Room, Bldg. 510

Hosted by: Anze Slosar

Strong gravitational lenses have become an important astronomical tool: they allow us to make accurate measurements of galaxy masses, they provide a magnified view of the distant universe, and they allow us to constrain cosmological parameters. In particular, the time delays in multiply-imaged quasar systems enable measurements of distance in the Universe each with around 5% precision. I will present our recent measurement of time delay distance in two galaxy-scale lens systems. For us to realize the potential of this cosmological probe, we need to increase the size of our lens sample, and continue to improve the accuracy of its analysis. I will discuss the potential of LSST to provide a sample of several hundred lensed quasars with well-measured time delays that would enable competitive and complementary constraints on Dark Energy, and describe our ongoing investigations of how to find lenses, infer their time delays and model their mass distributions accurately, and account for weak lensing effects from external mass structures.

48. RIKEN Lunch Seminar

"Jarzynski-type equalities in gambling: role of information in capital growth"

Presented by Yuji Hirono, Stony Brook

Thursday, April 16, 2015, 12:30 pm
Building 510 Room 2-160

Hosted by: Tomomi Ishikawa

49. High-Energy Physics & RIKEN Theory Seminar

"CKM physics with lattice QCD"

Presented by Aida El-Khadra, University of Illinois at Urbana-Champaign

Wednesday, April 15, 2015, 2 pm
Small Seminar Room, Bldg. 510

Hosted by: Chris Kelly

50. Nuclear Theory/RIKEN seminar

"Hydrodynamics Beyond the Gradient Expansion: Resurgence and Resummation"

Presented by Michael Heller, Perimeter Institute

Friday, April 10, 2015, 2 pm
Small Seminar Room, Bldg. 510

Hosted by: Soeren Schlichting

Consistent formulations of relativistic viscous hydrodynamics involve short lived modes, leading to asymptotic rather than convergent gradient expansions. In this talk I will consider the Mueller-Israel-Stewart theory applied to a longitudinally expanding quark-gluon plasma system and identify hydrodynamics as a universal attractor without invoking the gradient expansion. I will give strong evidence for the existence of this attractor and then show that it can be recovered from the divergent gradient expansion by Borel summation. This requires careful accounting for the short-lived modes which leads to an intricate mathematical structure known from the theory of resurgence.

51. HET/RIKEN seminar

"Radiation from the Dark Sector"

Presented by Tongyan Lin, University of Chicago

Wednesday, April 8, 2015, 2 pm
Small Seminar Room, Bldg. 510

Hosted by: Chien-Yi Chen

52. Physics Colloquium

"The Proton and the Future of Particle Physics"

Presented by Richard Hill, Univ. Chicago

Tuesday, April 7, 2015, 3:30 pm
Large Seminar Room, Bldg. 510

Hosted by: Peter Petreczky

The venerable proton continues to play a central role in fundamental particle physics. Neutrinos scatter from protons in neutrino oscillation experiments, Weakly Interacting Massive Particles (WIMPs) are expected to scatter from protons in dark matter searches, and electrons or muons are bound by protons in precision atomic spectroscopy. Our understanding of the proton is an obstacle to the success of next generation experiments hoping to discover CP violation in the lepton sector and determine the neutrino mass hierarchy, discover the particle nature of dark matter, or reveal new interactions such as those that violate lepton universality. In this talk I present (i) an overview of the current state of knowledge in the neutrino sector, and theoretical advances that will determine a crucial missing ingredient in the predicted signal process of neutrino-nucleus scattering at a Long Baseline Neutrino Facility (ii) the first complete calculation of the scattering cross section of a proton on a static electroweak source, which determines WIMP-nucleus scattering rates at underground direct detection experiments and (iii) the status of the proton radius puzzle, whose most "mundane" resolution requires a 5 standard deviation shift in the value of the Rydberg constant. I describe how each of these problems has spurred the development of powerful new methods in effective quantum field theory.

53. Condensed-Matter Physics & Materials Science Seminar

"2-dimensional Superconductivity at the LaAlO3/SrTiO3 Interface"

Presented by Jean-Marc Triscone, DQMP, University of Geneva, Switzerland

Tuesday, April 7, 2015, 1:30 pm
ISB Bldg. 734, Conf. Rm. 201 (upstairs)

Hosted by: Ivan Bozovic

The interface between LaAlO3 and SrTiO3, two good band insulators, which was found in 2004 to be conducting [1], and, in some doping range, superconducting with a maximum critical temperature of about 200 mK [2] is attracting of lot of attention. The electronic structure of the system displays signatures of confinement and of the d-character of the carriers. This electron liquid has a thickness of a few nanometers at low temperatures and a low electronic density. Being naturally sandwiched between two insulators, it is ideal for performing electric field effect experiments that allow the carrier density to be tuned and the phase diagram of the system to be determined [3]. I will discuss in this presentation superconductivity, the phase diagram of the system and the link with bulk doped SrTiO3, spin orbit [4], and an approach that allows superconducting coupling between different gases to be studied. I will also discuss recent thermopower measurements that allow access to localized electronic states [5]. [1] A. Ohtomo, H. Y. Hwang, Nature 427, 423 (2004). [2] N. Reyren, S. Thiel, A. D. Caviglia, L. Fitting Kourkoutis, G. Hammerl, C. Richter, C. W. Schneider, T. Kopp, A.-S. Ruetschi, D. Jaccard, M. Gabay, D. A. Muller, J.-M. Triscone and J. Mannhart, Science 317, 1196 (2007). [3] A. Caviglia, S. Gariglio, N. Reyren, D. Jaccard, T. Schneider, M. Gabay, S. Thiel, G. Hammerl, J. Mannhart, and J.-M. Triscone, Nature 456, 624 (2008). [4] A.D. Caviglia, M. Gabay, S. Gariglio, N. Reyren, C. Cancellieri, and J.-M. Triscone, Physical Review 104, 126803 (2010). [5] I. Pallecchi, F. Telesio, D. Li, A. Fête, S. Gariglio, J.-M. Triscone, A. Filippetti, P. Delugas, V. Fiorentini, and D. Marré, to appear in Nature Communications.

54. Nuclear Physics Seminar

"New Studies of Elastic Nucleon Form Factors"

Presented by Dr. Seamus Riordan, Stony Brook University

Tuesday, April 7, 2015, 11 am
Small Seminar Room, Bldg. 510

Hosted by: Jin Huang

The electromagnetic form factors of the nucleon provide experimental access to the underlying charge and magnetic moment distributions arranged by the strong nuclear force. These form factors provide excellent testing grounds for QCD and QCD-inspired models and are fundamentally important in understanding non-perturbative strong force physics. By studying them over a broad range of momentum transfers, they provide insight into the underlying mechanisms relevant to the generation of nucleon structure. At low Q2 there is presently a controversy regarding the charge radius measurements of the proton. At high Q2, scaling of the form factors are presently being studied in the context of a transition from soft QCD interactions. In this talk I will provide an overview of our present experimental of elastic nucleon form factors, review their context within current theoretical models, discuss upcoming future measurements at Jefferson Lab, in particular the Super Bigbite program.

55. C-AD Accelerator Physics Seminar

""Solid-State Laser Engineering for Inertial Confinement Fusion Laser Systems Applications""

Presented by Dr. Andrey Okishev

Friday, April 3, 2015, 4 pm
Bldg 911B., Large Conf.Rm., Rm. A202

"Solid-state laser concepts for ICF laser system applications including master oscillator, regenerative amplifier, OPO, and fiber-based front-end are discussed. Applications for the ICF laser system front-end, laser temporal diagnostics testing, laser damage testing, ASE suppression for OPCPA pump, energetic picosecond pulse generation without mode locking, cryogenic target layering, complex multi-FM pulses generation are described."

56. Nuclear Theory/RIKEN seminar

"Gravitational collapse, holography and hydrodynamics in extreme conditions"

Presented by Paul Chesler, Harvard University

Friday, April 3, 2015, 2 pm
Small Seminar Room, Bldg. 510

Hosted by: Soeren Schlichting

A remarkable observation from RHIC and the LHC is that the quark-gluon plasma produced in heavy-ion collisions behaves as a strongly coupled and nearly ideal liquid. Data also suggests that the debris produced by proton-nucleus collisions can also behave as a liquid. Understanding the dynamics responsible for the rapid equilibration of such tiny droplets is an outstanding problem. In recent years holography has emerged as a powerful tool to study non-equilibrium phenomena, mapping challenging quantum dynamics onto the classical dynamics of gravitational fields in one higher dimension. In the dual gravitational description the process of quark-gluon plasma formation and equilibration maps onto the process of gravitational collapse and black hole formation. I will describe how one can apply techniques and lessons learned from numerical relativity to holography and present recent work on holographic models of high energy collisions and the applicability of hydrodynamics to tiny droplets of quark-gluon plasma.

57. Particle Physics Seminar

"Measurement of the pion polarizability at COMPASS"

Presented by Jan Friedrich, Technische Universität München, Germany

Friday, April 3, 2015, 10 am
Small Seminar Room, Bldg. 510

Hosted by: Ketevi A. Assamagan

For more than a decade, the COMPASS experiment at the CERN Super Proton Synchrotron has been tackling the measurement of the electromagnetic polarizability of the charged pion, which describes the stiffness of the pion against deformation in electromagnetic fields. Previous experiments date back to the 1980's in Serpukhov (Russia), where the Primakoff method to study charged-pion interactions with quasi-real photons was first employed. Later also other techniques in photon-nucleon and photon-photon collisions were carried out at different machines. The COMPASS measurement demonstrates that the charged-pion polarizability is significantly smaller than the previous dedicated measurements, roughly by a factor two, with the smallest uncertainties realized so far. The pion polarisability is of fundamental interest in the low-energy sector of quantum chromodynamics. It is directly linked to the quark-gluon substructure and its dynamics in the lightest bound system of strong interaction.

58. Particle Physics Seminar

"Neutrino Oscillations with IceCube"

Presented by Tyce DeYoung, Michigan State University

Thursday, April 2, 2015, 3 pm
Small Seminar Room, Bldg. 510

Hosted by: Elizabeth Worcester

The IceCube Neutrino Observatory is the world's largest neutrino detector. Although designed to detect TeV " PeV scale neutrinos from astrophysical accelerators, IceCube's DeepCore infill array permits searches for dark matter and measurements of neutrino oscillations in the 10-100 GeV range. The most recent measurements of muon neutrino disappearance with IceCube DeepCore will be presented, and prospects for future neutrino physics measurements with IceCube and the proposed PINGU array will be discussed

59. RIKEN Lunch Seminar

"Spin-Orbit Coupling in an Unpolarized Heavy Nucleus"

Presented by Matt Sievert, BNL

Thursday, April 2, 2015, 12:30 pm
Building 510 Room 2-160

Hosted by: Daniel Pitonyak

The next-generation Electron-Ion Collider (EIC) will make high precision measurements of spin-dependent observables at high energies on nuclear targets. This unique nuclear physics laboratory will bring together access to the multitude of spin-spin and spin-orbit structures which can exist in hadronic targets, and the high color-charge densities which generate the most intense gluon fields permitted by quantum mechanics. The interplay between those two features gives rise to new physical mechanisms which translate these spin-orbit structures into the observed cross-sections, and it makes these mechanisms amenable to first-principles calculation. In this talk, I will discuss the spin-orbit structure of quarks within an unpolarized heavy nucleus in the quasi-classical approximation. The possibility of polarized nucleons with orbital motion inside the unpolarized nucleus generates nontrivial mixing between the spin-orbit structures of the nucleons, and the corresponding structures in the nucleus. This generic feature of a dense quasi-classical system leads to direct predictions testable at an EIC, and in principle allows direct access to the orbital angular momentum in the nucleus.

60. HET/RIKEN Seminar

"A Global Approach to Top-quark FCNCs"

Presented by Gauthier Durieux, Cornell University

Wednesday, April 1, 2015, 2 pm
Small Seminar Room, Bldg. 510

Hosted by: Chien-Yi Chen

61. Physics Colloquium

"Hot Jupiters: astrophysical laboratories for extreme weather"

Presented by Rosalba Perna, Stony Brook University

Tuesday, March 31, 2015, 3:30 pm
Large Seminar Room, Bldg. 510

Hosted by: Peter Petreczky

Hot Jupiters, a class of exoplanets orbiting in the proximity of their parent stars, are subjected to a strong irradiating flux that governs their radiative and dynamical properties. It is a regime which is not observed in the giant planets of our solar system. In this talk, I will describe current efforts to understand their radiative and dynamical properties, characterize their atmospheres by means of a variety of techniques, study the interaction of their fast, weakly ionized winds with the planetary magnetic field, and shed light on an evolutionary puzzle known as the problem of inflated radii.

62. Nuclear Physics Seminar

"Molten salt: towards the next generation of nuclear energy"

Presented by Dr. Ondrej Chvala, University of Tennessee

Tuesday, March 31, 2015, 11 am
Small Seminar Room, Bldg. 510

Hosted by: Jin Huang

Current nuclear powerplants use almost exclusively highly pressurized water as reactor coolant and heat transfer medium. This limits their operation to relatively low temperatures. Molten alkali-halide salts allow low pressure operation at high temperatures, improving thermal efficiency and operational safety. The talk will cover the history of molten salt reactor development, reasons for the renewed interest, and focus on recent developments of molten salt nuclear technologies in the U.S. and abroad.

63. C-AD Accelerator Physics Seminar

"High-Power Fiber Lasers for Cornell Energy Recovery LINAC"

Presented by Dr. Zhi Zhao, Cornell University

Monday, March 30, 2015, 4 pm
Bldg 911B, Large Conf. Rm. Rm.A202

Hosted by: John Skaritka

"In this talk, I will present a description of high-power fiber lasers and beam shaping systems that have been used to achieve low emittance and record high beam current in the Cornell energy recovery LINAC injector. Design, limitation, as well as power scaling of fiber lasers for the future accelerators will be discussed. "

64. Condensed-Matter Physics & Materials Science Seminar

"Printed nanocomposite capacitors for power conversion applications, and solution processed methods for producing ferroic complex oxide nanoparticles"

Presented by Stephen O'Brien, Department of Chemistry, The City college of New York, New York, NY 10031, Energy Institute, City University of New York, NY 10031

Monday, March 30, 2015, 11 am
Conference Room, Building 480

Hosted by: Yimei Zhu

I will give an overview of the metacapacitors project, an ARPA-E sponsored project that aims to improve efficiency, functionality and form factor of off-line power converters suitable for LED solid-state lighting, with a view to developing an attractive technology platform for load management and power conversion across a broad range of applications. Based on integrated switched-capacitor (SC) topologies, the project adopts an integrated approach from materials to devices to circuits. We designed capacitors based on high-dielectric nanocrystals, that can be prepared using high throughput microfabrication/nanotechnology techniques, ink deposition and multilayering. The capacitor dielectric, a nanocomposite composed of (Ba,Sr)TiO3 nanocrystals in polyfurfuryl alcohol (BST/PFA, _ > 20 , 100Hz - 1 MHz , loss < 0:01 , 20 kHz ), targets a high volumetric capacitance density and ripple current capability. The capacitors were board-integrated with a custom hybrid-switched-capacitor resonant (HSCR) DC-DC converter, tested and demonstrated to operate with high efficiency. The methodology for preparing the capacitor dielectric films relies on a novel method to prepare complex oxides, followed by evaporatively driven self-assembly into thin films. I'll review rational synthetic design, multigram scaling, and dispersion formulation design, as well as recent advances in the synthesis and characterization of novel multiferroic and ferroelectric complex oxides. STEPHEN O'BRIEN is an Associate Professor of Chemistry at City College New York and a member of the CUNY Energy Institute. He holds appointments on the Doctoral Faculty of the CUNY Graduate Center and Grove School of Engineering. Steve is a researcher in nanomaterials synthesis, properties and structural characterization: nanoparticle synthesis and self-assembly into superlattices, transition metal oxide nanomaterials, high k dielectrics/memory materials. He is published in over

65. C-AD Accelerator Physics Seminar

""Spin Dynamics Modeling in the AGS Based on a Stepwise Ray-Tracing Method""

Presented by Yann Dutheil, BNL

Friday, March 27, 2015, 4 pm
Bldg 911B, Large Conf. Rm. Rm. A202

"The AGS provides a polarized proton beam to RHIC. The beam is accelerated in the AGS from Gγ = 4.5 to Gγ = 45.5 and the polarization transmission is critical to the RHIC spin program. In the recent years, various systems were implemented to improve the AGS polarization transmission. These upgrades include the double partial snakes configuration and the tune jumps system. However, 100 % polarization transmission through the AGS acceleration cycle is not yet reached. Understanding the sources of depolarization in the AGS is critical to improve the AGS polarized proton performances. The complexity of beam and spin dynamics, which is in part due to the specialized Siberian snake magnets, drove a strong interest for original methods of simulations. For that, the Zgoubi code, capable of direct particle and spin tracking through field maps, was used to model the AGS. The Zgoubi model of the AGS will be introduced and recent results obtained through multiturn tracking will be shown. Selected example will highlight the relevance of the Zgoubi simulations to improve the polarization transmission in the AGS."

66. Particle Physics Seminar

"Nue appearance analysis in NOvA"

Presented by Jianming Bian, University of Minnesota

Thursday, March 26, 2015, 3 pm
Small Seminar Room, Bldg. 510

Hosted by: Elizabeth Worcester

The NOvA experiment is a long base-line accelerator based neutrino oscillation experiment. It uses the upgraded NuMI beam from Fermilab and measures electron neutrino appearance and muon neutrino disappearance at its far detector in Ash River, Minnesota. Goals of the experiment include measurements of theta13, mass hierarchy and the CP violating phase. NOvA has begun to take neutrino data and first neutrino candidates are observed in its far detector. This talk provides an introduction to the scientific reach of the experiment, the detector construction and the nue appearance analysis, as well as the first data in near and far detectors.

67. C-AD Accelerator Physics Seminar

""Beam-Beam Effects and Landau Damping in the LHC and HL-LHC""

Presented by Claudia Tambasco, CERN, Italy

Thursday, March 26, 2015, 2 pm
Bldg 911B, Large Conf. Rm. Rm. A202

Hosted by: Wolfram Fischer

"The Large Hadron Collider (LHC) at CERN is a high-energy circular hadron collider designed to provide a maximum center of mass energy of 14 TeV and a peak luminosity of L = 1e34-1e35 cm'2 s'1 . The LHC 2012 RUN has shown strong coherent transverse instabilities developing at top energy (4TeV) which where causing large particle losses and in many cases also beam dumps. Coherent modes driven by the machine impedance are normally Landau damped by the use of octupole magnets which are regularly powered to ensure enough detuning with amplitude. Also beam-beam effects contribute to the detuning with amplitude and they could therefore increase or decrease the Landau damping range of frequencies depending on the spread obtained from the octupoles. The interplay between impedance, Landau octupoles and beam-beam interactions defines the stability limits of the accelerator that can be evaluated by the so called stability diagrams. In the tune spread analysis there is no information on possible mechanisms which modify the particle distribution, second fundamental ingredient of the Landau damping. Therefore it is fundamental to explore experimentally, through Beam Transfer Function measurements, and with simulations the effects of different distributions to the stability diagrams. The High Luminosity Large Hadron Collider (HL-LHC) projects aims to extend the LHC discovery potential and it is designed to operate with beams of much higher brightness resulting in much stronger beam-beam interactions. Landau damping properties for this scenario are also presented."

68. HET/RIKEN seminar

"Flavored Dark Matter with Weak Scale Mediators"

Presented by Can Kilic, The University of Texas, Austin

Wednesday, March 25, 2015, 2 pm
Small Seminar Room, Bldg. 510

Hosted by: Chien-Yi Chen

All matter in the Standard Model appears in three generations, with an intricate flavor structure the origin of which is not well understood. This motivates the question whether distinct phenomenological features arise if dark matter (DM) also has a non-trivial flavor structure. In this talk I will review the experimental signatures of this scenario. In the case of lepton-flavored DM, I will argue that the generation of a lepton asymmetry at a high energy scale can also produce a DM asymmetry, which can strongly affect the sensitivity of direct detection experiments, and I will present novel signatures that can appear at colliders and in indirect detection experiments. I will also review the case of top quark-flavored DM with a distinct collider phenomenology including final states of top pairs and missing energy as well the possibility of displaced decays.

69. Physics Colloquium

"Discoveries that changed the world: 1932 - 1942 - James Chadwick & Lise Meitner"

Presented by Gerard Lander, EITU - Karlsruhe

Tuesday, March 24, 2015, 11 am
Large Seminar Room, Bldg. 510

Hosted by: Doon Gibbs

From the discovery of the neutron (1932) to the first demonstration of controlled fission (1942) was just ten years; a period that took physics from an occupation of a small number of eccentric gentlemen and (even fewer) ladies to something of concern to, and funding decisions of, Governments all over the world. The shadows of those tumultuous years are still with us, for better or worse. This talk will recount those ten years through the lives of James Chadwick (1891-1974) and Lise Meitner (1878-1968), contemporaries who played pivotal roles in the events, even though, partly because of their retiring personalities, they are often over-shadowed by "larger" figures.

70. Joint NT/RIKEN Seminar

"Flow-like behavior in small systems — Multi-parton interactions and color reconnection effects at the LHC"

Presented by Antonio Ortiz Velasquez, National Autonomous University of Mexico

Friday, March 20, 2015, 2 pm
Small Seminar Room, Bldg. 510

Hosted by: Soeren Schlichting

Collectivity in high multiplicity pp and p-Pb collisions is the most unexpected discovery at the LHC, its origin is still an open question. In heavy ion collisions, collectivity is attributed to final state effects due to the presence of a hot and dense QCD medium, and it is well described by viscous hydrodynamical calculations with fluctuating initial state geometries. Surprisingly, calculations which employ hydrodynamics reproduce qualitatively well the features of p-Pb data, but, the applicability of hydro in small systems faces conceptual problems. This is not the case of other approaches which do not require a medium to be formed and also are able to reproduce qualitatively well some features of data. In this talk it will be shown that multi-parton interactions and color reconnection (CR) produce flow-like effects in high multiplicity pp collisions. A study of the transverse momentum (pT) distribution of identified hadrons as a function of the event multiplicity will be presented. This comprises studies of the average pT vs hadron mass and number of constituent quarks, and a pT differential study using the Boltzmann-Gibbs Blast-Wave model. A comparison between hydro and color reconnection calculations will be presented. In this context, the results from the same study using LHC data (pp, p-Pb and Pb-Pb collisions) will be discussed.

71. Condensed-Matter Physics & Materials Science Seminar

"Graphene on Ir(111), adsorption and intercalation of Cs and Eu atoms"

Presented by Predrag Lazic, Rudjer Boskovic Institute, Croatia

Thursday, March 19, 2015, 1:30 pm
ISB Bldg. 734, Conf. Rm. 201 (upstairs)

Hosted by: Tonica Valla

Experimental and theoretical study of Cs and Eu atoms adsorption on graphene on Ir(111) will be presented [1,2]. Graphene on Ir(111) surface is an interesting system because graphene has almost pristine electronic structure in it due to its weak bonding character to iridum surface. The bonding is almost exclusively of the van der Waals type. However adding Cs or Eu atoms graphene gets doped and and nature of binding changes - especially in the case when the atoms intercalate. Density Functional Theory calculations with standard semilocal functionals (GGA) - fail to reproduce experimental findings even qualitatively. Only when the newly developed nonlocal correlation functional is used (vdW-DF) which includes van der Waals interactions, are the calculations in agreement with experiment, revelaing the mechanism of graphene delamination and relamination which is crucial for intercalation and trapping of atoms under the graphene. [1] M. Petrovic et al., Nat. Commun. 4, 2772 (2013). [2] S. Schumacher et al., Nano Lett. 13, 5013 (2013).

72. HET/RIKEN seminar

"Spontaneous CP violation and the strong CP problem"

Presented by Luca Vecchi, University of Maryland

Wednesday, March 18, 2015, 2 pm
Small Seminar Room, Bldg. 510

Hosted by: Chien-Yi Chen

73. RIKEN BNL

"The title of my talk is "How Jets and Two-Particle Correlations Impact Our Understanding of the Quark Gluon Plasma"

Presented by Megan Connors, Yale University

Wednesday, March 18, 2015, 2 pm
Building 510 Room 2-160

Hosted by: Samuel Aronson

Relativistic heavy ion collisions can reproduce the conditions necessary to form a hot and dense medium known as the Quark Gluon Plasma (QGP), the state of the universe immediately following the Big Bang, in which quarks and gluons are deconfined. Results from experiments at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC), which study the properties of the QGP, will be presented. This seminar will focus on two particle correlations and jet physics results in Pb-Pb and Au-Au collisions at the LHC and RHIC respectively and the prospects for such measurements at the proposed sPHENIX detector. In addition, the implications of using p-p or p-A systems as a reference for these A-A measurements will be discussed. Jets are the result of a hard scattering, which occurs early in the collision process, and probe how partons interact and lose energy in the medium. Two particle correlations are used to study jet physics and energy loss, as well as the underlying event. The interplay between the two is important for understanding how high momentum particles lose energy and for finding where that lost energy goes. To quantify the influence of the QGP on these measurements, it is important to have a good baseline measurement. A-A measurements are typically compared to expectations based on p-p collisions. Recent results from p-A collisions are used to quantify cold nuclear matter effects not captured in p-p collisions. However, p-A measurements have proven to be interesting in their own unexpected way which has implications for physics measurements at the future Electron Ion Collider.

74. Physics Colloquium

"Measuring Dark Matter and Dark Energy with Gravitational Lensing"

Presented by Erin Sheldon, BNL

Tuesday, March 17, 2015, 3:30 pm
Large Seminar Room, Bldg. 510

Hosted by: Morgan May

Gravitational lensing is the bending of light as it passes massive bodies. The amount of deflection is directly related to the mass of the lensing body and the geometrical configuration of the lens-source system. Typical lens configurations involve a distant background galaxy lensed by a much closer foreground galaxy, or cluster of galaxies. The lensing effect can be used to infer the mass of the lens, both luminous and dark matter. Lensing, as a purely geometrical phenomenon has become the most important way to measure the distribution of dark matter in the universe. I will discuss measurements I have made of the dark matter distribution in galaxies and clusters of galaxies using the lensing phenomenon. These measurements, the most precise to date, are consistent with the predictions of the cold dark matter model. Dark energy has accelerated the expansion of the universe at late times, and thus alters the relationship between the observed redshift of galaxies and their true distance from us. Lensing is sensitive to this redshift-distance relationship, and thus dark energy, since the amount of light deflection depends on the relative distances of lens and source. I will discuss the Dark Energy Survey (DES), a survey of the southern sky, now ending our second year of data taking. DES surveys larger volumes of the universe, and probes farther back in time than previous lensing surveys. With DES we will establish lensing as a competitive method to study dark energy. I will discuss preliminary results from DES using galaxy clusters as lenses and distant background galaxies as sources. I will end with a discussion of the new Large Synoptic Survey Telescope (LSST) survey, of which BNL is a member. LSST is a successor of DES, now entering the construction phase. With LSST we will bring lensing to maturity as a probe of dark energy.

75. Nuclear Physics Seminar

"Recent development of quarkonium production in p+p and p+A collisions"

Presented by Yan-Qing Ma, University of Maryland

Tuesday, March 17, 2015, 11 am
Small Seminar Room, Bldg. 510

Hosted by: Oleg Eyser

Although the next-to-leading order NRQCD calculation can solve many puzzles of heavy quarkonium production phenomena, it can neither describe data at very high nor very low transverse momentum (pT) region. At very high pT region, a double parton fragmentation formalism was proposed recently, which can systematically reorganize the expansion and resum large logarithms; while at very low pT region, a NRQCD+CGC framework was proposed to take into account the intrinsic transverse momentum and gluon saturation effects. I will talk about these theories and their application on p+p and p+A collisions from RHIC to LHC.

76. Particle Physics Seminar

"Search for Direct Top Squarks"

Presented by Walter Hopkins, University of Oregon

Monday, March 16, 2015, 3 pm
Small Seminar Room, Bldg. 510

Hosted by: Ketevi Assamagan

The results of a search for direct pair production of the scalar partner to the top quark using an integrated luminosity of 20/fb of proton-proton collision data at 8 TeV, recorded with the ATLAS detector at the LHC, are reported. The top squark is assumed to decay via stop -> top+LSP where LSP denotes the lightest neutralino in supersymmetric models. The search targets a fully hadronic final state in events with four or more jets and large missing transverse momentum. No significant excess over the Standard Model background prediction is observed, and exclusion limits are reported in terms of the top squark and LSP masses. In addition to the current results, prospects and plans for stop searches in the LHC Run 2 will be discussed.

77. Physics Colloquium

"DOUBLE BETA DECAY AND NEUTRINO MASSES"

Presented by Francesco Iachello, Yale University

Tuesday, March 10, 2015, 3:30 pm
Large Seminar Room, Bldg. 510

Hosted by: Peter Petreczky

The question of whether or not neutrinos are Majorana particles and, if so, what is their average mass remains one of the most fundamental problems in physics today. The average neutrino mass can be obtained from neutrinoless double beta decay. The inverse half-life for this process is given by the product of a phase space factor (PSF), a nuclear matrix element (NME) and whatever physics there is beyond the standard model. In this talk, the theory of double beta decay, both with and without the emission of neutrinos, will be reviewed, and recent calculations of the PSF and NME will be presented. From these and from experimental limits on the half-life of neutrinoless double beta decay, one can extract limits on the neutrino mass, both for the exchange of light (mνá1keV) and heavy (mνà1GeV) neutrinos. Current limits will be discussed. Finally, the question of how many neutrino species there are will be briefly addressed, including the possibility of sterile neutrinos with masses in the intermediate range keV-GeV.

78. Sustainable Energy Technologies Seminar

"Surfactant Free Synthesis of Plasmonic Nanoparticles and Their Application in Optical Detection of Explosives and Ions"

Presented by Devika Sil, Temple University, Philadelphia

Tuesday, March 10, 2015, 2 pm
ISB 734 2nd Floor Seminar Room 201

Hosted by: Matthew Eisaman

The localized surface plasmon resonance (LSPR), arising due to the collective oscillation of free electrons in metal nanoparticles, is a sensitive probe of the nanostructure and its surrounding dielectric medium. Synthetic strategies for developing surfactant free nanoparticles providing direct access to the metallic surface that harvest the localized surface plasmons will be discussed first followed by the applications. It is well known that the hot carriers generated as a result of plasmonic excitation can participate and catalyze chemical reactions. One such reaction is the dissociation of hydrogen. By the virtue of plasmonic excitation, an inert metal like Au can become reactive enough to support the dissociation of hydrogen at room temperature, thereby making it possible to optically detect this explosive gas.1 The mechanism of sensing is still not well understood. However, a potential hypothesis is that the dissociation of hydrogen may lead to the formation of a metastable gold hydride with optical properties distinct from the initial Au nanostructures, causing a reversible increase in transmission and blue shift in LSPR. It will also be shown that by tracking the LSPR of bare Au nanoparticles grown on a substrate, the adsorption of halide ions on Au can be detected exclusively. The shift in LSPR frequency is attributed to changes in electron density rather than the morphology of the nanostructures, which is often the case.

79. HET/RIKEN Seminar

"The Galactic Center Gamma-ray Excess: Have We Started to See Dark Matter"

Presented by Samuel McDermott, Stony Brook University

Wednesday, March 4, 2015, 2 pm
Building 510 SSR

Hosted by: Sally Dawson

80. C-AD Accelerator Physics Seminar

"Polarization Aperture Response for 250 GeV Ramps"

Presented by Dr. Vahid Ranjbad, BNL

Friday, February 27, 2015, 4 pm
Bldg 911B, Large Conf. Rm., Rm A202

"Through direct and lattice independent tracking we show how the polarization aperture can be greatly expanded by modifying the 453-nu intrinsic spin resonance next to the main 393+nu resonance. We also explore the conjecture that the structure of the aperture is related to the area of the parametric resonance regions based on the new formulation for the T-BMT equation (given in my recent PRSTAB paper http://journals.aps.org/prstab/pdf/10.110/PhysRevSTAB.18.014001) and how this might explain some of the apparent structure in the polarization profile measurements."

81. HET/BNL Lunch Time Talk

"Primordial non-Gaussianity is a crucial probe of inflationary physics"

Presented by Anze Slosar, BNL

Friday, February 27, 2015, 12 pm
Building 510 Room 2-160

Hosted by: Amarjit Soni

82. Particle Physics Seminar

"The ATLAS H-ZZ(*)-4l decay channel"

Presented by Kalliopi Iordanidou, Columbia University, Nevis Laboratories

Friday, February 27, 2015, 11 am
Small Seminar Room, Bldg. 510

Hosted by: Ketevi A. Assamagan

The H->ZZ(*)4l decay channel is the experimentally cleanest signature for the Higgs boson production at the LHC (CERN). The selection of the candidates, the data driven background estimation methods and the property measurements of the Higgs boson are presented using the ATLAS Run-I data. Prospect expectations are explored for the High Luminosity LHC (HL-LHC) scenario.

83. Particle Physics Seminar

"Coherent Charged Pion Production in ArgoNeuT"

Presented by Tingjun Yang, Fermilab

Thursday, February 26, 2015, 3 pm
Small Seminar Room, Bldg. 510

Hosted by: Elizabeth Worcester

I will present the first cross section measurements for charged current coherent pion production by neutrinos and antineutrinos on argon. These measurements are performed using the ArgoNeuT detector exposed to the NuMI beam at Fermilab. The results are in a good agreement with the theoretical predictions from GENIE and NuWro.

84. Special Nuclear Physics/HEP Seminar

"Nuclear parton distributions in theory"

Presented by Adam Freese, Florida International University, Miami, FL

Thursday, February 26, 2015, 10 am
Building 510 Room 2-160

Hosted by: Thomas Ulrich

Quantum chromodynamics has been extremely successful in describing a multitude of high-energy experiments with aid from the use of universal parton distribution functions. PDFs for the free proton are fairly well-constrained by experiment, but nuclear PDFs require elaboration. Three ingredients are necessary to obtain a nuclear PDF theoretically: (1) an account of the nuclear momentum distribution that includes the latest results regarding short range correlations; (2) a model of how nucleons immersed in the nuclear medium are modified at a quark-gluon level; and (3) the application of QCD evolution to connect the low momentum resolution scales at which the first two ingredients are obtained to the high momentum transfer scales relevant to the LHC and the EIC. These three ingredients will be described in detail, and an example of their application to proton-nucleus collisions at LHC energies will be provided.

85. High-Energy Physics & RIKEN Theory Seminar

"The Search for Relic Neutrinos"

Presented by Mariangela Lisanti, Princeton

Wednesday, February 25, 2015, 2 pm
Small Seminar Room, Bldg. 510

Hosted by: Sally Dawson

86. Physics Workshop

"Brain Circulation Workshop"

Wednesday, February 25, 2015, 9 am
Large Seminar Room, Bldg. 510

Hosted by: Rob Pisarski

This is the third workshop for a visiting program between the Japanese Society for the Promotion of Science and the Nuclear, Lattice Gauge, and High Energy Theory groups at Brookhaven. The grant, termed a Brain circulation program, is between Dr. Tetsuo Hatsuda, Chief Scientist at RIKEN, and his colleagues from RIKEN, Kyoto University, and Tsukuba University, and is designed to allow young scientists to visit BNL. In this workshop young scientists from both Japan and BNL will discuss their work.

87. Nuclear Physics Seminar

"Understanding flow fluctuations with Principal Components"

Presented by Derek Teaney, Stony Brook University

Tuesday, February 24, 2015, 11 am
Small Seminar Room, Bldg. 510

Hosted by: Jiangyong Jia

We perform a Principal Component Analysis (PCA) of $v_3(p_T)$ in event-by-event hydrodynamic simulations of Pb+Pb collisions at the LHC. The PCA procedure identifies two dominant contributions to the two particle correlation function, which together capture 99.9\% of the squared variance. We find that the subleading flow (which is the largest source of flow factorization breaking in hydrodynamics) is predominantly a response to the radial excitations of a third-order eccentricity. We present a systematic study of the hydrodynamic response to these radial excitations in 2+1D viscous hydrodynamics. Finally, we construct a good geometrical predictor for the orientation angle and magnitude of the leading and subleading flows using two Fourier modes of the initial geometry.

88. Condensed-Matter Physics & Materials Science Seminar

"Non-equilibrium electronic structure and ultrafast dynamics of solid materials"

Presented by Uwe Bovensiepen, Univ. Duisburg-Essen, Germany

Friday, February 20, 2015, 1:30 pm
ISB, Bldg. 734, Conf. Rm. 201 (upstairs)

Hosted by: Jonathan Rameau

Optical excitations in solid materials decay typically on femto- to picosecond time scales due to interactions which lead to a redistribution of the excess energy among the electronic, the lattice, and the spin subsystem, before final dissipation. We perform pump-probe experiments in order to analyze these excitations and the action they generate through their relaxation directly in the time domain. In this talk time- and angle-resolved photoemission (tr-ARPES) results which probe the excited state with energy and momentum sensitivity on complex materials like charge density wave compounds [1] and high temperature superconductors [2,3] will be discussed. In the prototype charge density wave material RTe3 (R=Ho, Tb, Dy) we obtained a momentum dependent analysis of the time dependent gap function (k,t) which sheds lights on the amplitude mode and the interaction responsible for the charge density wave formation. In the iron based superconductor material BaFe2As2 the optical excitation induces oscillations in the chemical potential linked to the coherent A1g phonon which modulates the pnictogen height and electronic correlations. In the cuprates pump-induced changes are observed below and above Tc. We obtained evidence for considerable photo-doping effects based on transient changes in the Fermi momentum kF upon optical excitation. Remarkably, the observed changes follow predictions based on chemical doping, which suggests time- and angle-resolved photoemission as a novel method to differentially probe the Fermi surface of complex materials. [1] L. Rettig, J.-H. Chu, I. R. Fisher, U. Bovensiepen, M. Wolf, Faraday Discuss. 171, 1 (2014). [2] J. Rameau, S. Freutel, L. Rettig, I. Avigo, M. Ligges, Y. Yoshida, H. Eisaki, J. Schneeloch, R. D. Zhong, Z. J. Xu, G. D. Gu, P. D. Johnson, U. Bovensiepen, Phys. Rev. B 89, 115115 (2014). [3] L. X. Yang, G. Rohde, T. Rohwer, A. Stange, K. Hanff, C

89. Condensed-Matter Physics & Materials Science Seminar

"Electronic phase separation and magnetic phase behavior in the Ru-doped spin-orbit Mott insulator Sr3Ir2O7"

Presented by Chetan Dhital, Oak Ridge National Laboratory

Wednesday, February 18, 2015, 11 am
ISB Bldg. 734, Conf. Rm. 201 (upstairs)

Hosted by: Mark Dean

Recent theoretical and experimental studies have predicted a very interesting electronic phase diagram in 5d iridate system arising due to interplay of spin orbit interaction and the electronic correlation. Spin-orbit Mott phase is one such electronic phase realized in Ruddelsden-Popper (RP) series [Srn+1IrnO3n+1] oxides. Sr3Ir2O7 (n=2) and Sr2IrO4 (n=1) are two representative candidates of this series. Although their ground state properties are studied to some extent, very little is known regarding how the properties of their antiferromagnetic, insulating, parent states evolve upon carrier substitution. One way of experiencing the strength and relevance of electronic correlation in any condensed matter system is by doping charge carriers. The presence of electronic correlations in the host system determines the fate of the dopant and hence stabilizes a new electronic/magnetic ground state. I will discuss about importance of electronic correlations in one such doped system Sr3 (Ir1-xRux) 2O7 using combined neutron scattering, electric transport and magnetization techniques. Our findings demonstrate that correlation effects felt by carriers introduced within in a 5d Mott phase remain robust enough to drive electron localization, a key ingredient in emergent phenomena such as high temperature superconductivity and enhanced ferroic behavior. References: [1]. Dhital, Chetan, et al. "Spin ordering and electronic texture in the bilayer iridate Sr3Ir2O7." Physical Review B 86.10 (2012): 100401. [2]. Dhital, Chetan, et al. "Neutron scattering study of correlated phase behavior in Sr2IrO4." Physical Review B 87.14 (2013): 144405. [3]. Dhital, Chetan, et al. " Carrier localization and electronic phase separation in a doped spin-orbit-driven Mott phase in Sr3 (Ir1"xRux) 2O7 (Nature communications,2014)

90. RIKEN/BNL Lunch Time Talk

"Bose-Einstein Condensation, Isotropization, and Thermalization in Overpopulated Systems"

Presented by Jinfeng Liao, Indiana University / RBRC

Thursday, February 12, 2015, 12:30 pm
Building 510 Room 2-160

Hosted by: Tomomi Ishikawa

We discuss recent progress, using the kinetic theory framework, in understanding the non-equilibrium evolution of overpopulated systems that resemble the glasma during the early stage of heavy ion collisions. We analyze a number of important factors that influence the course of thermalization in such systems, and in particular their consequences for the nontrivial dynamics driving Bose-Einstein Condensation as well as the isotropization. We discuss recent progress, using the kinetic theory framework, in understanding the non-equilibrium evolution of overpopulated systems that resemble the glasma during the early stage of heavy ion collisions. We analyze a number of important factors that influence the course of thermalization in such systems, and in particular their consequences for the nontrivial dynamics driving Bose-Einstein Condensation as well as the isotropization.

91. High-Energy Physics & RIKEN Theory Seminar

"Electric Dipole Moments, New Physics, and (lattice) QCD"

Presented by Vincenzo Cirigliano, Los Alamos

Wednesday, February 11, 2015, 2 pm
Small Seminar Room, Bldg. 510

Hosted by: Sally Dawson

In this talk I will discuss the role of electric dipole moments (EDMs) as probes of physics beyond the Standard Model (BSM). In the first part of the talk I will present an overview of the physics reach of various searches and I will discuss the complementarity of different EDM probes. In the second part of the talk I will discuss ongoing work towards the computation of the BSM-induced neutron and proton EDM using lattice Quantum ChromoDynamics.

92. Condensed-Matter Physics & Materials Science Seminar

"Spin-orbital separation in the quasi-one-dimensional Mott insulator Sr2CuO3"

Presented by Jeroen van den Brink, Institute for Theoretical Solid State Physics, IFW Dresden and Department of Physics, TU Dresden, Germany

Monday, February 9, 2015, 1:30 pm
ISB 201 seminar room

Hosted by: Weiguo Yin

When viewed as an elementary particle, the electron has spin and charge. When binding to the atomic nucleus, it also acquires an angular momentum quantum number corresponding to the quantized atomic orbital it occupies. Even if electrons in solids form bands and delocalize from the nuclei, in Mott insulators they retain their three fundamental quantum numbers: spin, charge and orbital. The hallmark of one-dimensional physics is a breaking up of the elementary electron into its separate degrees of freedom. The separation of the electron into independent quasi-particles that carry either spin (spinons) or charge (holons) was first observed fifteen years ago. Here we report observation of the separation of the orbital degree of freedom (orbiton) using resonant inelastic X- ray scattering on the one-dimensional Mott insulator Sr2CuO3. We resolve an orbiton separating itself from spinons and propagating through the lattice as a distinct quasi-particle with a substantial dispersion in energy over momentum, of about 0.2 electronvolts, over nearly one Brillouin zone [1]. [1] J. Schlappa, K. Wohlfeld, K. J. Zhou, M. Mourigal, M. W. Haverkort, V. N. Strocov, L. Hozoi, C. Monney, S. Nishimoto, S. Singh, A. Revcolevschi, J.-S. Caux, L. Patthey, H. M. Rønnow, Jeroen van den Brink and T. Schmitt, Nature 485, 82 (2012).

93. Condensed-Matter Physics & Materials Science Seminar

"tba"

Presented by tba

Thursday, February 5, 2015, 4:30 pm
2nd floor conference room, Bldg 734

Hosted by: Robert Konik

94. High-Energy Physics & RIKEN Theory Seminar

"Ab initio calculation of the neutron-proton mass difference"

Presented by Antonin Portelli, University of Southampton, UK

Wednesday, February 4, 2015, 2 pm
Small Seminar Room, Bldg. 510

Hosted by: Sally Dawson

95. C-AD Accelerator Physics Seminar

"Optics Measurements in Low Emittance Rings Using Turn-byTurn Data"

Presented by Panagiotis Zisopoulos, University of Upsala, Sweden

Monday, February 2, 2015, 11:30 am
Bldg 911B, Large Conf. Rm., Rm. A202

Hosted by: Kewisch/Peggs

96. C-AD Accelerator Physics Seminar

"Beam-based Diagnostic of Octupolar Component in CLIC Accelerating Structure"

Presented by James Ogren, University of Upsala, Sweden

Monday, February 2, 2015, 11 am
Bldg 911B, Large Conf. Rm., Rm A202

Hosted by: Peggs/Kewisch

97. C-AD Accelerator Physics Seminar

""Proton Spin Tracking with Symplectic Orbit Motion""

Presented by Dr. Yun Luo, BNL

Friday, January 30, 2015, 4 pm
Bldg 911B Large Conf. Rm, Rm A202

"Symplectic integration had been adopted for orbit tracking in code SimTrack, which has been extensively used for dynamic aperture calculation with beam-beam interaction for the Relativistic Heavy Ion Collider (RHIC). Recently spin motion for protons and synchrotron radiation for electrons have been added to this code. In this talk, the speaker will first review existing spin tracking codes used at BNL, then introduce symplectic integration of orbit motion and implementation of spin tracking based on Thomas-BMT equation. Several tracking examples for AGS (Alternating Gradient Synchrotron), RHIC, and eRHIC will be presented."

98. Particle Physics Seminar

"Silicon Sensor R&D for the ATLAS HL-LHC Upgrade"

Presented by Daniel Muenstermann, University of Geneva

Thursday, January 29, 2015, 3 pm
Small Seminar Room, Bldg. 510

Hosted by: Ketevi Assamagan

In the coming years, the LHC will be upgraded to provide much higher luminosity. This implies increased radiation damage, occupany and pile-up for the ATLAS experiment and requires the replacement of the current Inner Detector with an improved all-silicon tracker.

99. Condensed-Matter Physics & Materials Science Seminar

""Progress of RCE processed REBCO Coated Superconductors in Korea""

Presented by Dr. Sang-Soo Oh, Superconductivity Research Center, Korea Electrotechnology Research Institute, Korea, Republic of (South)

Friday, January 23, 2015, 11 am
Bldg. 480 conference room

Hosted by: Qiang Li

100. Brookhaven Lecture

"501st Brookhaven Lecture: Negative Particles for Positive Breakthroughs: Characterizing Electrons in Novel Materials at NSLS-II"

Presented by Ignace Jarrige, Photon Sciences Directorate

Wednesday, January 21, 2015, 4 pm
Berkner Hall Auditorium

Hosted by: Thomas Watson

During the 501st Brookhaven Lecture, Ignace Jarrige will discuss different ways electrons behave and affect unique materials' properties. He will then explain how the new Soft Inelastic X-ray Scattering (SIX) beamline—an extra-long beamline he is developing at NSLS-II—will measure how x-rays excite atomic bonds in new materials researchers are inventing around the world. Jarrige and his collaborators will use this new tool to unravel mysteries of electrons' collective behavior with unprecedented accuracy as they witness emerging phenomena such as superconductivity—the ability to conduct electricity with zero resistance—magnetism, and other phenomena that could lead to faster trains, more powerful computer processors, and far more efficient electrical grids.

101. C-AD Accelerator Physics Seminar

"The future of isotope production on medium and high energy beams"

Presented by Boris Zhuikov, Institute for Nuclear Research of the Russian Academy of Sciences

Wednesday, January 21, 2015, 2:30 pm
C-AD, Bldg. 911B, Large Conference Room

Hosted by: Berndt Mueller

102. Center for Functional Nanomaterials Workshop

"Joint Workshop on Nanoscience and Nanotechnology Opportunities for Academia & High Tech Industry (NNO2015)"

Monday, January 5, 2015, 9 am
Seminar Room, Building 735

Hosted by: James H. Dickerson

103. Office of Educational Programs Event

"High School Research Program (HSRP) Poster Session 2014"

Tuesday, December 2, 2014, 4 pm
Berkner Hall Auditorium

Hosted by: Scott Bronson

Brookhaven National Laboratory's primary focus as an institution is research and development. Students participate in ongoing programs where a BNL scientist mentors a student on a research project during a six week summer session. Students may also work during the academic year, usually to complete their project.

104. Brookhaven Lecture

"498th Brookhaven Lecture: 'Vector Boson Scattering: Watching the Higgs Boson at Work with the ATLAS Particle Detector'"

Presented by Marc-Andre Pleier, Physics Department at Brookhaven Lab

Wednesday, October 22, 2014, 4 pm
Berkner Hall Auditorium

Hosted by: Thomas Watson

105. Brookhaven Lecture

"497th Brookhaven Lecture: 'Super-Computing Fundamental Particle & Nuclear Physics'"

Presented by Taku Izubuchi, Physics Department at Brookhaven Lab

Wednesday, September 24, 2014, 4 pm
Berkner Hall Auditorium

Hosted by: Allen Orville

106. Condensed-Matter Physics & Materials Science Seminar

"Band Structure Engineering in Mg2Si1-xSnx and (Bi1-xSbx)2Te3: from Bulk to Surface Transport"

Presented by Wei Liu, Department of Physics, University of Michigan

Tuesday, August 19, 2014, 10:30 am
Bldg. 480 Conference Room

Hosted by: Qiang Li

Composition tuning in compound semiconductors allows for band structure engineering, which opens many avenues in fundamental and applied research. Here, I will show the application of band structure engineering in optimizing the electronic properties of bulk thermoelectric materials as well as probing the surface transport of topological insulator thin films. The main motivation of current thermoelectric research is to optimize the figure of merit ZT, so that the efficiency can be improved in (i) recovering waste industrial heat as well as (ii) providing local cooling of electronic devices. However, it is a challenge to independently tune the thermoelectric parameters that lead to high ZTs. We have found that Mg2Si1-xSnx thermoelectric material not only shows excellent thermoelectric performance but also exhibits decoupled Seebeck coefficient (α) and electrical conductivity (σ). We discover the convergence of two conduction bands in this material, which enhances the density-of-states effective mass and α in a large temperature range, without any detrimental effect on σ. Thus, a significantly improved power factor (PF = α2σ) is achieved, which results in a record high ZT in this material. Another material example with interesting consequences of band structure engineering is (Bi1-xSbx)2Te3. This material has become a mainstream material in the research of 3D topological insulators due to their potential to obtain surface transport protected by time-reversal-symmetry. I will show that using molecular beam epitaxy technique we can (i) tune the Bi/Sb ratio and (ii) control the thickness (as thin as several quintuple layers), which allow the observation of a dramatic distinction in electronic transport between high quality films and their bulk counterparts. An insulating-like regime has been obtained, which has enabled studies of magneto-resistance and thermoelectric properties associated with surface states.

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