Bulletin of the American Physical Society
2016 Fall Meeting of the APS Division of Nuclear Physics
Volume 61, Number 13
Thursday–Sunday, October 13–16, 2016; Vancouver, BC, Canada
Session DF: Ultrarelativistic Heavy-Ion Collisions |
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Chair: Li Yi, Yale University Room: Pavilion Ballroom A |
Friday, October 14, 2016 10:30AM - 10:42AM |
DF.00001: Chiral magnetic effect and anomalous transport from real-time lattice simulations Soeren Schlichting, Sayantan Sharma, Mark Mace, Niklas Mueller We present a first-principle study of anomaly induced transport phenomena by performing real-time lattice simulations with dynamical fermions coupled simultaneously to non-Abelian $SU(Nc)$ and Abelian $U(1)$ gauge fields. We investigate the behavior of vector and axial currents during a sphaleron transition in the presence of an external magnetic field, and demonstrate how the interplay of the Chiral magnetic (CME) and Chiral separation effect (CSE) lead to the formation of a propagating wave. We also analyze the quark mass dependence of these phenomena and extract spectral information about the carriers of axial and vector charge. [Preview Abstract] |
Friday, October 14, 2016 10:42AM - 10:54AM |
DF.00002: Quark-gluon plasma effects on hadrons in AdS/QCD Sean Bartz, Theodore Jacobson The AdS/CFT correspondence has succeeded in describing qualitatively many features of non-perturbative QCD. An approach known as bottom-up AdS/QCD uses a dilaton field to break conformal symmetry, introducing confinement and describing well the features of hadronic spectra at zero temperature. Introducing a black hole into the AdS metric allows for the study of thermodynamic properties of QCD, mimicking the behavior of hadrons interacting with a hot, dense medium such as the quark-gluon plasma produced in heavy ion collisions. We present an improved AdS/QCD model for meson and glueball spectra at finite temperature and baryon chemical potential. The spectra match the experimental and lattice data qualitatively well at low temperature, but we also find some subtleties in connecting to the best zero-temperature models. We find a melting temperature for light mesons that is below the current estimates for the deconfinement temperature. Finally, we examine the melting and jet-quenching of heavy quarkonia, which more commonly act as probes of the QGP in heavy ion collisions. [Preview Abstract] |
Friday, October 14, 2016 10:54AM - 11:06AM |
DF.00003: Rapidity Density Distributions of Identified Protons from the RHIC Beam Energy Scan at STAR Christopher Flores A principle goal of the Beam Energy Scan (BES) at the Relativistic Heavy-Ion Collider is to explore the properties of nuclear matter in temperature and baryon chemical potential ($\mu_{B}$) phase space. The baryon chemical potential is sensitive to the degree of stopping that occurs during the interaction of two heavy ions. Previous measurements of the transverse mass spectra of protons at mid-rapidity have provided insights into how the $\mu_{B}$ evolves as a function of collision energy. In this analysis we propose to study baryon stopping by investigating the yield of protons in the longitudinal dimension. The transverse mass spectra of protons will be extracted for a broad range of rapidities and for multiple BES collision energies. These spectra will then be used to construct the rapidity density distributions of protons. Finally observed trends as function of collision energy will be discussed. [Preview Abstract] |
Friday, October 14, 2016 11:06AM - 11:18AM |
DF.00004: The STAR beam energy scan phase II physics and upgrades. Flemming Videbaek The second phase of the Beam Energy Scan at RHIC will occur in 2019-2020 and will explore with precision measurements in the part of the QCD phase diagram where baryon densities are high. The program will examine energy regime of interest and turn the trends observed in phase-I into conclusions. This will be discussed in context of some of the key measurements, kurtosis of net-protons that could pinpoint the position of a critical point, measurements of directed flow of baryons vs. energy that might prove a softening of the EOS , and chiral restoration in the di-lepton channel. The measurements will be possible with an order of magnitude better statistics thanks to the electron cooling upgrade of RHIC, and the addition of the iTPC, Event Plane, and endcap TOF upgrades to STAR. [Preview Abstract] |
Friday, October 14, 2016 11:18AM - 11:30AM |
DF.00005: Rapidity Correlation Structure in Nuclear Collisions Christopher Zin, Sean Gavin, George Moschelli The forces that drive the nuclear collision system towards local thermal equilibrium leave few observable traces. Heavy ion experiments report a range of features widely attributed to the hydrodynamic flow of a near-equilibrium quark gluon plasma. In particular, measurements of azimuthal anisotropy provide the most comprehensive support for the hydrodynamic description of these systems. In search of the source of this flow, we turned to smaller proton-proton, proton-nucleus and deuterium-nucleus collisions, expecting to find this effect absent. Instead, these collisions show an azimuthal anisotropy that is comparable to the larger ion-ion systems. How can we learn about the mechanisms that give rise to hydrodynamics if every available collision system exhibits flow? We show that measurements of the rapidity dependence of transverse momentum correlations can be used to determine the characteristic time $\tau_\pi$ that dictates the rate of isotropization of the stress energy tensor, as well as the shear viscosity $\nu = \eta/sT$. We formulate methods for computing these correlations using second order dissipative hydrodynamics with noise. Current data are consistent with $\tau_\pi/\nu \sim 10$ but targeted measurements can improve this precision. [Preview Abstract] |
Friday, October 14, 2016 11:30AM - 11:42AM |
DF.00006: Photon-triggered jet reconstruction at the STAR experiment Derek Anderson Jets \--- collimated sprays of hadrons \--- are produced by the hard scattering of partons in the early stages of a heavy-ion collision, which makes them powerful probes of the hot, dense medium created in such a collision. In particular, the study of away-side jets in events tagged by high transverse-momentum "direct photons" should provide a measurement of the energy lost by a parton as it traverses the medium\footnote{X.-N. Wang, Z. Huang, and I. Sarcevic, Phys. Rev. Lett. 77, 231 (1996)}. Since the direct photon does not interact strongly with the medium, it closely approximates the initial energy of the outgoing parton from which it scattered. This talk will give an overview of the methods with which STAR is pursuing such a measurement. A brief review of the results of $\gamma$-hadron correlations\footnote{arXiv:1604.01117v2 [nucl-ex]} and a brief update on the status of the ongoing $\gamma$-jet analysis in STAR will be presented. [Preview Abstract] |
Friday, October 14, 2016 11:42AM - 11:54AM |
DF.00007: PHENIX Low Momentum Direct Photon Analysis Wenqing Fan The PHENIX experiment operates with one of the major detectors at the RHIC collider. One of the major goals of PHENIX is to identify and study Quark Gluon Plasma (QGP). Direct photons turn out to be an excellent probe due to their small interaction cross section with the collision produced medium hence carrying information of its properties from the space-time production points. In the PHENIX direct photon measurement, a large excess of low-$p_{T}$ photons in Au+Au collisions at 200 GeV is discovered compared to reference p+p collisions, which has been interpreted as thermal radiation from the QGP and hadron-gas (HG) medium. At the same time the excess photons have a large azimuthal anisotropy, expressed as Fourier coefficients v2 and v3. Measurements at a lower collision energy may provide new insight on the origin of the low-$p_{T}$ direct photons. In the experiment the current effort is to reduce the experimental uncertainties in Au+Au and p+p collisions via the photons$’$ external conversion to di-electron pairs, and measure the direct photon yield in Cu+Au and p+Au collisions at 200 GeV as well as the yield in Au+Au collisions at lower 39 GeV and 62.4 GeV. We will present the improvements and the status of the ongoing analyses. [Preview Abstract] |
Friday, October 14, 2016 11:54AM - 12:06PM |
DF.00008: Prospects for Jet Measurements with the sPHENIX Detector John Haggerty sPHENIX is a proposed experiment at RHIC with uniform electromagnetic and hadronic calorimetry and precision tracking in a central barrel which is capable of measuring jets, jet correlations and upsilons at the highest RHIC luminosities in heavy ion collisions in the early 2020's. Results from a program of prototype detector tests in test beams will be shown, as well as expectations from simulation of the capabilities for jet measurements in heavy ion collisions. [Preview Abstract] |
Friday, October 14, 2016 12:06PM - 12:18PM |
DF.00009: ABSTRACT WITHDRAWN |
Friday, October 14, 2016 12:18PM - 12:30PM |
DF.00010: Heavy flavor studies at forward and backward rapidities in Cu+Au collisions with PHENIX detector. Cesar da Silva Asymmetric Cu+Au collisions at $\sqrt{s_{NN}}$=200 GeV performed at RHIC in 2012 open an opportunity to study particle yields in the presence of different mixtures of initial and final state nuclear effects by using probes measured from negative to positive rapidity regions. Heavy flavor yields may be affected by initial state effects on gluons and energy loss in the final state hot medium. The 2012 run was the first where the Forward Vertex Detector (FVTX) was operating. This detector allows the identification of D and B mesons from displaced vertex measurements. Results on B-meson nuclear modification through its J/$\psi$ decay channel will be presented along with the status of the analysis of semi-leptonic decays of charm and bottom yields. [Preview Abstract] |
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