Bulletin of the American Physical Society
APS April Meeting 2015
Volume 60, Number 4
Saturday–Tuesday, April 11–14, 2015; Baltimore, Maryland
Session B15: Ultra-Relativistic Heavy Ions |
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Sponsoring Units: DNP Chair: Justin Frantz, Ohio University Room: Key 11 |
Saturday, April 11, 2015 10:45AM - 10:57AM |
B15.00001: Measurements of di-hadron correlations and azimuthal anisotropies in the BES at RHIC by STAR Liao Song The Beam Energy Scan (BES) program at the Relativistic Heavy Ion Collider (RHIC) aims to vary the temperature and baryon-chemical potential of the medium formed from heavy-ion collisions, by colliding Au nuclei at energies from 7.7 GeV to 200 GeV (center of mass energy per nucleon). In doing so, it hopes to create a map of the Quantum ChromoDynamical (QCD) phase diagram of nuclear matter, and determine at which temperature Quark Gluon Plasma (QGP) formation occurs. Spatial inhomogeneities in the initial state of the collision can create pressure gradients in the QGP, which induce anisotropies among produced particles, known as azimuthal anisotropy. These anisotropies manifest themselves as the ridge in di-hadron correlations, which has been extensively studied at the top the RHIC energies and the LHC. We will present some preliminary measurements of di-hadron correlations from$\sqrt{s_{NN}}$= 7.7, 11.5, 19.6, 27 and 39 GeV BES data, and the azimuthal anisotropy parameters $v_2\{2\}$ and $v_3\{2\}$ obtained from the $\Delta\eta\Delta\phi$ correlation function, and compare with previous STAR results at top (or higher) RHIC energies. We will also look at the $\Delta\eta$ gap dependence and the energy dependence of these anisotropy parameters. [Preview Abstract] |
Saturday, April 11, 2015 10:57AM - 11:09AM |
B15.00002: A New Observable for Di-Jet Di-hadron Jet Suppression Bing Xia, Justin Frantz In Relativistic Heavy Ion collisions of small species type, effects of jet suppression from jet energy loss. We present a new two particle correlations observable, and discuss its systematics and interpretations from model studies, as well as comparison to existing measurements at RHIC and LHC. [Preview Abstract] |
Saturday, April 11, 2015 11:09AM - 11:21AM |
B15.00003: Methods for Determining Elliptic Flow of Isolated Photons and $\pi^0$'s Tyler Danley We present methods for measurements of second order flow coefficients and derivations of reaction plane dependent efficiencies of isolated photons and $\pi^0$'s in Relativistic Heavy Ion Collisions. The method involves isolation cuts similar to those used in direct photon identification where the energy is summed inside an angular cone and cut if greater than a threshold energy. We show that this will result in a reaction plane dependent efficiency. We derive and verify azimuthal single and two particle correlation functions, including this efficiency, up to harmonic second order. We show that the standard v2 extraction method is only sensitive to an effective $v_{2}$, which includes the sum of true $v_2$ and the $v_2$ of the isolation efficiency, which is generally negative. We will also present the status of applying these methods to PHENIX $\sqrt{s_{NN}} = 200\ GeV$ Au+Au data. [Preview Abstract] |
Saturday, April 11, 2015 11:21AM - 11:33AM |
B15.00004: Anisotropic hydrodynamics for conformal Gubser flow Mohammad Nopoush, Radoslaw Ryblewski, Michael Strickland We derive the equations of motion for a system undergoing boost-invariant longitudinal and azimuthally-symmetric transverse ``Gubser flow'' using leading-order anisotropic hydrodynamics. This is accomplished by assuming that the one-particle distribution function is ellipsoidally-symmetric in the momenta conjugate to the de Sitter coordinates used to parameterize the Gubser flow. We then demonstrate that the $SO(3)_q$ symmetry in de Sitter space further constrains the anisotropy tensor to be of spheroidal form. The resulting system of two coupled ordinary differential equations for the de Sitter-space momentum scale and anisotropy parameter are solved numerically and compared to a recently obtained exact solution of the relaxation-time-approximation Boltzmann equation subject to the same flow. We show that anisotropic hydrodynamics describes the spatio-temporal evolution of the system better than all currently known dissipative hydrodynamics approaches. In addition, we prove that anisotropic hydrodynamics gives the exact solution of the relaxation-time approximation Boltzmann equation in the ideal, $\eta/s \rightarrow 0$, and free-streaming, $\eta/s \rightarrow \infty$, limits. [Preview Abstract] |
Saturday, April 11, 2015 11:33AM - 11:45AM |
B15.00005: ABSTRACT WITHDRAWN |
Saturday, April 11, 2015 11:45AM - 11:57AM |
B15.00006: Anisotropic Jet Quenching in semi-Quark-Gluon Plasmas with Magnetic Monopoles Jiechen Xu, Jinfeng Liao, Miklos Gyulassy We present a new jet quenching framework, CUJET3.0, that is shown to simultaneously account for both the high $p_T$ single inclusive hadron suppression $R_{AA}$ and its azimuthal anisotropy $v_2$ in heavy ion collisions at both RHIC and LHC energies. CUJET3.0 generalizes our previous pQCD/HTL based CUJET2.0 model that couples running coupling DGLV jet energy loss to (2+1)D viscous hydrodynamic fluids, and it includes two new nonperturbative effects in the QCD transition temperature range $T\sim \rm 140-250$ MeV: (1) the Polyakov loop suppression of color-electric scattering (aka ``semi-QGP'' of Pisarski et al) and (2) the enhancement of scattering due to emergent magnetic monopoles near $T_c$ (aka ``magnetic scenario'' of Liao and Shuryak). The parameters of the model are constrained by lattice QCD data. We find that the CUJET3.0 jet transport coefficient $\hat{q}(E,T)/T^3$ peaks near $T_c$ by a factor $\sim 4$ above previous perturbative pQCD/HTL estimates, approaching hybrid AdS/SYM holography of Liu et al, but it has very strong nonconformal $E$ and $T$ dependence up to $T\sim 400$ MeV. Extrapolating down to $E=2$ GeV, we find a striking new connection between bulk perfect fluidity with $\eta/s\sim 0.1$ near $T_c$ and high $p_T$ high $T$ perturbative jet quenching. [Preview Abstract] |
Saturday, April 11, 2015 11:57AM - 12:09PM |
B15.00007: Prospect of Non-Prompt J/$\psi $ Measurements at STAR Zaochen Ye Heavy quarks (charm and bottom) are excellent probes to study the properties of the Quark-Gluon Plasma (QGP), a hot, dense, and strongly interacting nuclear matter created in heavy-ion collisions. \newline Measurements of non-prompt J/$\psi $ production from B hadron decays in heavy-ion collisions can provide information about interactions between bottom quarks and the QGP, and the properties of the hot medium itself. The Heavy Flavor Tracker (HFT) and Muon Telescope Detector (MTD) have been fully installed into the STAR experiment and taken data since the beginning of 2014. The HFT significantly improves the track impact parameter resolution, and thus allows separation between the prompt and non-prompt J/$\psi $. The MTD enables STAR to identify muons, and thus allows J/$\psi $ studies in the dimuon decay channel. In this talk we will describe simulation studies for non-prompt J/$\psi $ at STAR in both the dielectron and dimuon decay channels. The projections for the nuclear modification factor R$_{AA}$ and elliptic flow v$_{2}$ of non-prompt J/$\psi $ will be presented. [Preview Abstract] |
Saturday, April 11, 2015 12:09PM - 12:21PM |
B15.00008: Quarkonia production in pPb collisions at CMS C. Christopher Ferraioli The CMS experiment at the LHC has measured quarkonia production in proton-lead collisions at $\sqrt{s_{NN}} = 5.02$ TeV. The results provide an important baseline for ultrarelativistic heavy-ion collisions by investigating cold nuclear matter effects on quarkonia production. The behavior of quarkonia production is studied as a function of transverse momentum and pseudorapidity and shows suppression relative to proton-proton collisions in specific phase spaces, suggesting the presence of nuclear effects. [Preview Abstract] |
Saturday, April 11, 2015 12:21PM - 12:33PM |
B15.00009: Non-photonic electron production in p$+$p collisions at $\surd s =$ 200 GeV Xiaozhi Bai High precision measurements of heavy flavor production in proton-proton collisions are instrumental to test the validity and constrain the parameters of pQCD calculations of heavy quark production. They also provide a baseline for the interpretation of heavy flavor production in heavy-ion collisions. In this talk, we present an improved measurement of non-photonic electron (NPE) production from semi-leptonic decay of open heavy flavor hadrons in proton-proton collisions at $\surd $s$=$200 GeV by the STAR experiment at the Relativistic Heavy Ion Collider. The results cover a wide range of transverse momentum, 0.2\textless p$_{\mathrm{T}}$\textless 12 GeV/c. The results for 2.5\textless p$_{\mathrm{T}}$\textless 12 GeV/c are based on about 24 pb$^{-1}$ of data triggered on energy deposited in the electromagnetic calorimeter, while the results for 0.2\textless p$_{\mathrm{T}}$\textless 2.5 GeV/c are extracted using about 300 M minimum-bias events. The measured NPE production cross-section is compared to previous STAR and PHENIX experimental results, as well as pQCD model calculations. [Preview Abstract] |
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