October 2015  

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OCT
7
Today
BSA Distinguished Lecture
"Universe or Multiverse?"
Presented by Andrei Linde, Stanford University
4 pm, Berkner Hall Auditorium
Wednesday, October 7, 2015, 4:00 pm
Hosted by: Peter Wanderer
Cosmological observations show that the universe is very uniform on the maximally large scale accessible to our telescopes. The best theoretical explanation of this uniformity is provided by the inflationary theory. Andrei Linde will briefly describe the status of this theory in view of recent observational data. Rather paradoxically, this theory predicts that on an extremely large scales, much greater than what we can see now, the world may look totally different. Instead of being a single spherically symmetric balloon, our universe may look like a "multiverse," a collection of many different exponentially large balloons ("universes") with different laws of lowenergy physics operating in each of them. The new cosmological paradigm, supported by developments in string theory, changes the standard views on the origin and the global structure of the universe and on our own place in the world.
OCT
8
Thursday
CondensedMatter Physics & Materials Science Seminar
"TBATopological NodalLine Fermions in Strong SpinOrbit Metal PbTaSe2"
Presented by TayRong Chang, National Tsing Hua University Taiwan, Taiwan
1:30 pm, ISB Bldg. 734, Conf. Rm. 201 (upstairs)
Thursday, October 8, 2015, 1:30 pm
Hosted by: Wei Ku
In a typical threedimensional metal, the lowenergy excitations are found on a twodimensional closed Fermi surface in momentum space. Topological semimetals, by contrast, can support onedimensional Fermi lines or zerodimensional FermiWeyl points, at locations in momentum space, where the valence and conduction bands touch. While the degeneracy points in Weyl semimetals are robust against any perturbation that preserves translational symmetry, nodal lines require protection by additional crystalline symmetries such as mirror reflection. In this talk, I will demonstrate the prediction of topological nodalline states in the noncentrosymmetric compound singlecrystalline PbTaSe2 with strong spinorbit coupling based on the firstprinciples electronic structure calculations. Remarkably, the spinorbit nodal lines in PbTaSe2 are not only protected by the reflection symmetry but also characterized by an integer topological invariant. Our theoretical analysis illustrate the physical mechanism underlying the formation of the topological nodalline states and associated surface states. The calculated surface states for (001) surface with Pbtermination are in good agreement with angleresolved photoemission (ARPES) measurements [1]. [1] arXiv:1505.03069, G. Bian, T.R. Chang, R. Sankar, et al.
OCT
9
Friday
Special Nuclear Theory Seminar
"Inclusive Hadron Production as a Probe of Saturation Physics on the Energy Frontier"
Presented by David Zaslavsky, Central China Normal University
11 am, Small Seminar Room, Bldg. 510
Friday, October 9, 2015, 11:00 am
Hosted by: Soeren Schlichting
With a foundation of almost two decades of theoretical research, the saturation formalism is widely considered a strong candidate to describe the behavior of smallx gluons in highenergy collisions. However, the formalism has proven difficult to test. There is a pressing need for precise numerical results from the saturation formalism to use in comparisons with collider data. Fortunately, recent progress in the cross section for inclusive hadron production in pA collisions shows that it may be just the kind of precise result the community needs. The calculation of the NLO corrections, starting in 2012, achieved impressive reductions in the theoretical and numerical uncertainties, although the result becomes negative at high pâŠ¥. Still, precise predictions at moderate pâŠ¥ can be made and tested, and could be strong evidence toward showing the viability of the saturation model. In this talk, I introduce the recent modifications to the dipole splitting functions that complete the NLO corrections and help offset the negativity observed in earlier results. I'll also present the latest numerical results for the full LO+NLO cross section, including the first comparison with LHC pilot run data. For forward rapidity at both RHIC and the LHC, we have found excellent agreement with the data throughout the range in which the calculation is valid.
OCT
13
Tuesday
Physics Colloquium
"Random Matrices in Physics"
Presented by Hans A. Weidenmuller, MaxPlanckInstitut fur Kernphysik, Heidelberg, Germany
3:30 pm, Large Seminar Room, Bldg. 510
Tuesday, October 13, 2015, 3:30 pm
Hosted by: Robert Pisarski
What can we say about a physical system when we know next to nothing about it? In classical physics, the principles of thermodynamics and a few systemspecifc parameters suce to make predictions. In quantum physics, random matrices have similar predictive power. That approach { referred to as randommatrix theory { has found wide applications in recent years, in quantum physics and beyond. The use of random matrices will be motivated, such matrices will be dened. Applications of random matrices in quantum chaos, in complex manybody systems, in disordered systems and in quantum chromodynamics will be presented. Furher applications in physics and mathematics will be briefly mentioned.
OCT
14
Wednesday
Instrumentation Division Seminar
"Nanopattern MultiWell Amorphous Selenium Detectors: towards realizing largearea avalanche gain with picosecond time resolution"
Presented by Amir H. Goldan, Stony Brook University
2:30 pm, Large Conference Room, Bldg. 535
Wednesday, October 14, 2015, 2:30 pm
Soon after the Nobel prize winning invention of the gasfilled multiwire proportional chamber (MWPC) by Charpak, and parallel to developments in microelectronics, a great deal of research was stimulated to develop the highest granularity gaseous detectors for achieving the highest spatial resolution. Solidstate detectors, on the other hand, can have three ordersofmagnitude higher density, and thus, they yield much smaller detector dimensions with substantially higher spatial and temporal resolution. Inspired by Charpak's MWPC and its micropattern variants, and parallel to developments in nanoelectronics, we propose a novel solidstate detector that utilizes amorphous selenium (aSe) as the photoconductive film. ASe is a roomtemperature wide bandgap semiconductor that is readily produced uniformly over large area at substantially lower cost compared to crystalline solids (e.g., crystalline Si). It is the only amorphous material that produces avalanche gain at high fields and because only holes become hot carriers, avalanche selenium devices are linearmode devices with a very low excess noise. Commercially, avalanche gain in aSe enabled the development of the first optical camera with more sensitivity than human vision and, for example, capable of capturing astronomical phenomena such as auroras and solar eclipses. ASe has âˆ¼90% detection efficiency in the blue wavelength which makes it ideal to be coupled to blueemitting scintillators for highenergy radiation detection. Finally, selenium films are physically evaporated and enable integration of the detector with the CMOS readout electronic on the same die. The major drawback of aSe is its poor timeresolution and low carrier mobility due to shallowtraps, problems that must be circumvented for applications such as timeofflight (TOF) imaging. Thus, we propose a nanopattern multiwell aSe detector to enable the utilization of both avalanche multiplication gain and unipolar timedifferential (UTD) cha
OCT
15
Thursday
CondensedMatter Physics & Materials Science Seminar
Presented by Sergey Zvyagin, High Magnetic Field Laboratory, Helmholtz Center Dresden, Germany
1:30 pm, Building 734, Room 201
Thursday, October 15, 2015, 1:30 pm
Hosted by: Cedomir Petrovic
Spin dynamics in triangularlattice antiferromagnets Cs2CuBr4 and Cs2CuCl4: highfield ESR studies Sergei Zvyagin Dresden High Magnetic Field Laboratory (HLD) HelmholtzZentrum DresdenRossendorf, Dresden, Germany A spin1/2 Heisenberg antiferromagnet (AF) on a triangular lattice is the paradigmatic model in quantum magnetism and in the focus of recent experimental and theoretical studies. Here, we present results of highfield electron spin resonance (ESR) studies of spin1/2 Heisenberg AFs Cs2CuCl4 and Cs2CuBr4 with distorted triangularlattice structures in magnetic fields up to 50 T [1]. In the magnetically saturated phase, quantum fluctuations are fully suppressed, and the spin dynamics is defined by ordinary magnons. This allows us to accurately describe the magnetic excitation spectra in both materials and, using the harmonic spinwave theory, to determine their exchange parameters. The approach has a broader impact and can be potentially used for any quantum magnet with reduced (e.g., by the staggered DzyaloshinskiiMoriya interaction) translational symmetry, resulting, as predicted, in emergence of a new exchange mode above Hsat. We found that a substantial zerofield energy gap, Î"~9.5 K, observed in the lowtemperature excitation spectrum of Cs2CuBr4, is present below and well above TN, being a characteristics of lowdimensional spincorrelated state. The experimental data are compared with results of model spinwavetheory calculations for spin1/2 triangular lattice AF. This work was supported by the DFG. [1] S. A. Zvyagin, D. Kamenskyi, M. Ozerov, J. Wosnitza, M. Ikeda, T. Fujita, M. Hagiwara, A. I. Smirnov, T. A. Soldatov, A. Ya. Shapiro, J. Krzystek, R. Hu, H. Ryu, C. Petrovic, and M. E. Zhitomirsky, Phys. Rev. Lett. 112, 077206, 2014
OCT
19
Monday
Healthfest Program Free Trial Fitness Classes all Week
12 pm, Vairous Locations see BERA Website for Locations
Monday, October 19, 2015, 12:00 pm
Hosted by: Christine Carter
Free Trial BERA Classes Try out the many BERA Fitness Classes that are offered onsite for free during this HealthFest week! For more information, go to www.bnl.gov/bera or https://www.bnl.gov/bera/recreation/fitness.asp
OCT
20
Tuesday
Healthfest Program Free Trial Fitness Classes all Week
12 pm, Various Locations see BERA Website for Locations
Tuesday, October 20, 2015, 12:00 pm
Hosted by: Christine Carter
Free Trial BERA Classes Try out the many BERA Fitness Classes that are offered on site for free during this HealthFest week! For more information, go to www.bnl.gov/bera or https://www.bnl.gov/bera/recreation/fitness.asp
OCT
20
Tuesday
CondensedMatter Physics & Materials Science Seminar
"TBA"
Presented by Sasa Dordevic, University of Akron
1:30 pm, Building 734, Room 201
Tuesday, October 20, 2015, 1:30 pm
Hosted by: Cedomir Petrovic
Infrared and magnetooptical studies of topological insulators Spectroscopic techniques are an important tool in studies of novel materials. I will review recent infrared and magnetooptical studies of 3D topological insulators Bi2Se3, Bi2Te3, Sb2Te3 and Bi1xSbx. A number of issues will be discussed, such as the cyclotron resonance and its field dependence, electronic inhomogeneities, and electronphonon coupling. We find that in Bi2Se3 charge carriers are indeed strongly coupled to an optical phonon, causing its asymmetric (Fano) lineshape. Moreover, we show that the asymmetry of the phonon can be switched from negative to positive, with the application of magnetic field. This is the socalled Fano q reversal, which to the best of our knowledge has not been observed before in topological insulators.
OCT
21
Wednesday
Healthfest Program Free Trial Fitness Classes All Week
12 pm, Various LOcations See BERA Website for Locations
Wednesday, October 21, 2015, 12:00 pm
Hosted by: Christine Carter
Free Trial BERA Classes Try out the many BERA Fitness Classes that are offered on site for free during this HealthFest week! For more information, go to www.bnl.gov/bera or https://www.bnl.gov/bera/recreation/fitness.asp
OCT
21
Wednesday
CondensedMatter Physics & Materials Science Seminar
"Three dimensional topological semimetal Cd3As2: insights from magnetooptical spectroscopy"
Presented by Ana Akrap, University of Geneva, Switzerland
1:30 pm, Bldg. 480 Conf. Room
Wednesday, October 21, 2015, 1:30 pm
Hosted by: Chris Homes
Cd3As2 is a threedimensional Dirac semimetal, with two Dirac cones around the Gamma point shifted away from each other along the (001) direction. It is known that the Dirac cones appear due to band inversion, although their exact scale is not clear at the moment. I will talk about zerofield optical conductivity, and highfield magnetoreflectivity of this material, and address some of the open questions regarding the band structure.
OCT
22
Thursday
Healthfest Program Free Trial Fitness Classes all Week
12 pm, Various Locations see BERA Website for Locations
Thursday, October 22, 2015, 12:00 pm
Hosted by: Christine Carter
Free Trial BERA Classes Try out the many BERA Fitness Classes that are offered onsite for FREE during this HealthFest week! For more information, go to www.bnl.gov/bera or https://www.bnl.gov/bera/recreation/fitness.asp
OCT
22
Thursday
Particle Physics Seminar
"Light Sterile Neutrinos: An Experimental Overview"
Presented by Jonathan Link, Center for Neutrino Physics, Virginia Tech
3 pm, Small Seminar Room, Bldg. 510
Thursday, October 22, 2015, 3:00 pm
Hosted by: Elizabeth Worcester
Persistent, unproven hints of an eVscale sterile neutrino have been around since the late 1990's, when the LSND signal was shown to be incompatible with the emerging 3neutrino oscillation framework. More recent results from MiniBooNE and T2K as well as reanalyses of reactor neutrino and gallium source data continue to suggest the possibility of this new physics, but no experiment has been able to definitively demonstrate or for that matter rule out their existence. This talk will review the current state of the sterile neutrino and examine one possible experimental test using a new reactor neutrino detector technology designed to address the particular challenges of a shortbaseline reactor neutrino experiment.
OCT
23
Friday
Nuclear Theory Seminar
"Thermal photons from a modern hydrodynamical model of heavy ion collisions"
Presented by JeanFrancois Paquet, Stonybrook University
2 pm, Small Seminar Room, Bldg. 510
Friday, October 23, 2015, 2:00 pm
Hosted by: Soeren Schlichting
Early fluiddynamical calculations of direct photon spectra and momentum anisotropy were found to be systematically smaller than measurements from the RHIC and the LHC, an observation that became known as the "direct photon puzzle". I will show that the use of a modern hydrodynamical model of heavy ion collisions and of the latest photon emission rates greatly improves agreement with both ALICE and PHENIX data, supporting the idea that thermal photons are the dominant source of direct photon momentum anisotropy in heavy ion collisions. The eventbyevent hydrodynamical model used includes, for the first time, both shear and bulk viscosities, along with second order couplings between the two viscosities. Calculations using different photon emission rates will be shown, including one that takes into account the effect of confinement on photon emission. The effect of both shear and bulk viscosities on the photon rates will be shown to have a measurable effect on the photon momentum anisotropy.
NOV
3
Tuesday
Office of Educational Programs Event
"SciEd Day"
8 am, Berkner Hall Auditorium
Tuesday, November 3, 2015, 8:00 am
Hosted by: Aleida Perez
Educators can choose a workshop that suits their grade level and interest. They will meet BNL scientific staff, tour a research facility and participate in a labbased activity that is grounded in research at BNL. In addition, educators can choose a facility to visit.
NOV
5
Thursday
Particle Physics Seminar
"LAr TPC data reconstruction"
Presented by Dorota Stefan, CERN/NCBJ Warsaw Poland
3 pm, Small Seminar Room, Bldg. 510
Thursday, November 5, 2015, 3:00 pm
Hosted by: Elizabeth Worcester
In recent years, there is much interest in building massive liquid argon time projection (LAr TPC) detectors to measure among others CP violation in leptonic sector, search for nucleon decay and study a corecollapse supernova via neutrinos. Data collected by ICARUS and ArgoNuet proved that LAr TPC calorimetric and spatial resolutions are excellent. The detector technology with no doubts is much advanced, resulting with plans for the next generation of liquid argon experiments: the short baseline (SBN) and the long baseline (DUNE) are on the horizon. The LAr TPC evolved from the bubble chambers preserving the high resolution of tracking. Data analysis requires automatic event reconstruction that can understand and efficiently use the high granularity images provided by detector. The talk will cover the most recent advances in the reconstruction techniques, and also possible ways of developments since we are still on the way towards the ultimate tool for the optimal data analysis.
NOV
6
Friday
Nuclear Theory/RIKEN Seminar
"Linearly resummed hydrodynamics from gravity"
Presented by Yanyan Bu, Ben Gurion University of the Negev
2 pm, Small Seminar Room, Bldg. 510
Friday, November 6, 2015, 2:00 pm
Hosted by: Soeren Schlichting
Using fluid/gravity correspondence, we study allorder resummed hydrodynamics in a weakly curved spacetime. The underlying microscopic theory is a finite temperature \mathcal{N}=4 superYangMills theory at strong coupling. To linear order in the amplitude of hydrodynamic variables and metric perturbations, the fluid's stressenergy tensor is computed with derivatives of both the fluid velocity and background metric resummed to all orders. In addition to two viscosity functions, we find four curvature induced structures coupled to the fluid via new transport coefficient functions, which were referred to as gravitational susceptibilities of the fluid (GSF). We analytically compute these coefficients in the hydrodynamic limit, and then numerically up to large values of momenta. We extensively discuss the meaning of all order hydrodynamics by expressing it in terms of the memory function formalism, which is also suitable for practical simulations. We also consider GaussBonnet correction in the dual gravity, which is equivalent to some 1/N corrections in the dual CFT. To leading order in the GaussBonnet coupling, we find that the memory function is still vanishing.
NOV
20
Friday
HET/RIKEN Lunch Seminar
"Collider Phenomenology of the Right Handed Heavy Neutrinos"
Presented by Arindam Das, University of Alabama
12 pm, Building 510 Room2160
Friday, November 20, 2015, 12:00 pm
Hosted by: Amarjit Soni
We study the collider signature of pseudoDirac heavy neutrinos in the inverse seesaw scenario, where the heavy neutrinos with mass at the electroweak scale can have sizable mixings with the Standard Model neutrinos, while providing the tiny light neutrino masses by the inverse seesaw mechanism. Based on a simple, concrete model realizing the inverse seesaw scenario, we fix the model parameters so as to reproduce the neutrino oscillation data and to satisfy other experimental constraints, assuming two typical flavor structures of the model and the different types of hierarchical light neutrino mass spectra. For completeness, we also consider a general parametrization for the model parameters by introducing an arbitrary orthogonal matrix and the nonzero Dirac and Majorana phases. We perform a parameter scan to identify an allowed parameter region which satisfies all experimental constraints. With the fixed parameters, we analyze the heavy neutrino signal at the LHC through trilepton final states with large missing energy and at the ILC through a single lepton plus dijet with large missing energy.
DEC
3
Thursday
Particle Physics Seminar
"Measurements Of CrossSection Of Charge Current Inclusive Of Antineutrino Scattering Off Nucleons Using Carbon, Iron, Lead And Scintillator At Minerva Gr 2GEV < Ev < 20GEV"
Presented by Laza Rakotondravohitra, University Of Antananarivo/Fermilab
3 pm, Small Seminar Room, Bldg. 510
Thursday, December 3, 2015, 3:00 pm
Hosted by: Ketevi Assamagan
MINERvA (Main INjector Experiment for vA) is a neutrino scattering experiment in the NuMI highintensity neutrino beam at the Fermi National Accelerator Laboratory. MINERvA was designed to make precision measurements of low energy neutrino and antineutrino cross sections on a variety of different materials (plastic scintillator, C, Fe, Pb, He and H2O). The experiment will provide important inputs, both in support of neutrino oscillation searches and as a pure weak probe of the nuclear medium. In this talk , we present a preliminary results of measurements of antineutrino inclusive cross section ratios on different nuclei as a function of Bjorken x
DEC
17
Thursday
Particle Physics Seminar
"Search for Higgs Bosons produced in association with top quarks with the ATLAS detector"
Presented by Professor Vivek Jain, SUNY Albany
3 pm, Small Seminar Room, Bldg. 510
Thursday, December 17, 2015, 3:00 pm
Hosted by: Ketevi Assamagan
Due to the large measured mass of the top quark, the Yukawa coupling of the top quark (yt) is much stronger than that of other quarks. The observation of the tÂ¯tH production mode would allow for a direct measurement of this coupling, to which other Higgs production modes are only sensitive via loop effects. Since yt is expected to be close to unity, it is also argued to be the quantity that might give insight into the scale of new physics. Using various Higgs decay modes, we report on the status of this search using data collected with the ATLAS detector at 7 and 8 TeV collision energies.