Bulletin of the American Physical Society
2015 Fall Meeting of the APS Division of Nuclear Physics
Volume 60, Number 13
Wednesday–Saturday, October 28–31, 2015; Santa Fe, New Mexico
Session NG: Ultrarelativistic Heavy Ions II |
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Chair: Michael McCumber, Los Alamos National Laboratory Room: Peralta |
Saturday, October 31, 2015 8:30AM - 8:42AM |
NG.00001: Anisotropic Flow analysis methods at small collision systems Shengquan Tuo, Qiao Xu, Julia Velkovska Measurements of anisotropic flow in relativistic heavy ion collisions probe the properties of QGP and the initial conditions. The discovery of charged particle anisotropic flow in small systems like pPb, dAu and He3Au collisions poses a question of what is the smallest droplet of hot QCD matter with liquid-like behavior. This question is difficult to answer without understanding the behavior of various flow analysis methods in small charged particle multiplicities with small values of anisotropic flow. We present a systematic examination of various methods including two and multi-particle correlations around the flow turn-on conditions. [Preview Abstract] |
Saturday, October 31, 2015 8:42AM - 8:54AM |
NG.00002: Search for long range angular correlations in high-multiplicity p+p collisions at $\sqrt{s}=200$ GeV from PHENIX Qiao Xu Long range angular correlations have been found in $d+Au$ and $^{3}He+Au$ collisions at RHIC energies, and in $p+p$ and $p+A$ collisions at LHC energies. To have a better understanding of whether quark-gluon plasma could be formed and collective behavior could arise in small systems motivates this study to see if such correlations also exist in $p+p$ collisions at RHIC energies. With the implementation of a high-multiplicity trigger using the forward silicon detector(FVTX), the PHENIX collaboration has taken several hundred million high-multiplicity events for $p+p$ collisions at $\sqrt{s} = 200$ GeV. In this talk we present the current status of two-particle angular correlation studies for charged hadrons emitted in $p+p$ collisions at a center-of-mass energy of 200 GeV. Charged particle multiplicity and transverse momentum dependence of correlations are discussed. [Preview Abstract] |
Saturday, October 31, 2015 8:54AM - 9:06AM |
NG.00003: PHENIX results on flow observables in Cu$+$Au collisions at $\surd $sNN $=$ 200 GeV Brennan Schaefer High-energy collisions of asymmetric, large nuclei offer a unique window into many aspects of excited medium formation and evolution. Unlike symmetric collisions, an asymmetric system can have non-zero odd-order moments in its average transverse distribution of participants; and, the patterns of participants from the two nuclei can have different shapes on average. The PHENIX experiment has measured particle production from Cu$+$Au collisions at RHIC at full energy ($\surd $sNN $=$ 200 GeV) during the 2012 running period. We report here measurements of azimuthal anisotropies v1, v2 and v3 (directed, elliptic and triangular flow) for inclusive and identified charged hadrons produced at mid-rapidity in Cu$+$Au collisions. Implications for diagnosing a variety of unique initial-state geometry effects will be discussed. [Preview Abstract] |
Saturday, October 31, 2015 9:06AM - 9:18AM |
NG.00004: Two-Particle Correlations in $p$+$p$ and $p$+Au Collisions with the MPC+MPC-EX detector at RHIC-PHENIX Nathan Grau PHENIX has installed a Si-W preshower (MPC-EX) to the existing PbWO$_4$ electromagnetic calorimeter (MPC) in the forward $3.0<|\eta|<3.8$ direction to significantly enhance the position detection of electromagnetic showers. The enhanced position detection allows for the detection of $\pi^0$s to much higher energy and transverse momentum than with the MPC alone. Single and multi-particle production in this $\eta$ and $p_T$ region will allow PHENIX to probe lower in $x$ and higher in $Q^2$ than previously available. We present the current status of two-particle correlations in both $p+p$ and $p$+Au using where at least one of the pair is an identified $\pi^0$ in the MPC+MPC-EX and how that informs our understanding of the initial state of nuclei. [Preview Abstract] |
Saturday, October 31, 2015 9:18AM - 9:30AM |
NG.00005: Comparison of Hydrodynamic Calculations of Heavy Ion Collisions with Different Equations of State Ron Soltz, Scott Moreland The QCD Equation of State (EoS) is an essential ingredient for the hydrodynamic models used to study heavy ion collisions. Recent results by the HotQCD and Wuppertal-Budapest collaborations lattice gauge calculations of the QCD EoS at the continuum limit show good agreement within errors. However it is unknown whether current errors are sufficient for current simulations or whether further improvements are needed. We explore this question by performing hydrodynamic calculations with the VISHNU 2+1D hydrodynamic code with fluctuating initial conditions and UrQMD cascade code for the two EoS calculations and a sampling of EoS curves within the given errors. Comparisons are made to spectra ($\pi$, K, p), flow ($v_2, v_3$), and azimuthally averaged HBT radii for 200~GeV Au+Au collisions. Relative variations in the results and comparisons to data where appropriate will be presented and discussed. [Preview Abstract] |
Saturday, October 31, 2015 9:30AM - 9:42AM |
NG.00006: Single Transverse Spin Asymmetries for Forward Neutrons in $\surd $s $=$ 200 GeV p$+$p, p$+$Al and p$+$Au collisions at the PHENIX experiment at RHIC Douglas Fields The Zero-Degree Calorimeters (ZDCs) at RHIC detect neutrons along the beam direction on either side of each interaction point. An additional Shower Maximum Detector (SMD) provides position information of the hadronic shower. The combination of these allows each experiment to look at the phi-asymmetry of forward neutrons in relation to the transverse spin direction of the proton beam travelling in the direction of that ZDC. Large single-spin asymmetries have been previously reported in p$+$p collisions. During the RHIC Run-15, for the first time RHIC delivered polarized proton collisions with Au and Al, allowing for the determination of the single-spin asymmetries with these heavier (and more neutron rich) species. We will present the current status of these studies at the PHENIX experiment. [Preview Abstract] |
Saturday, October 31, 2015 9:42AM - 9:54AM |
NG.00007: High pT Charged Hadron Spectrum in Au+Au Collisions at 200 GeV as Measured by PHENIX Jason Bryslawskyj The suppression of single hadrons still provides one of the strongest constraints on energy loss mechanisms in the Quark-Gluon Plasma. Currently the best measurement at RHIC of single particle suppression comes from neutral pions. Charged hadrons have independent sources of systematic uncertainty and can thus provide additional constraints. Off-vertex background from photon conversions and weak decays, which mimick high $p_T$ particles, have limited the measurement of charged hadrons to $p_T < 10$ GeV/c at PHENIX. These background sources can be rejected by the silicon vertex tracker upgrade (VTX) allowing the measurement of the charged hadron spectrum out to a significantly higher momentum. The VTX is capable of performing precision measurements of the distance of closest approach of a track to the primary vertex (DCA). Off-vertex photon conversions and weak decays are vetoed with the VTX by rejecting tracks with large DCA. The status of high-$p_T$ charged tracking and associated high-$p_T$ charged hadron spectrum will be reported. [Preview Abstract] |
Saturday, October 31, 2015 9:54AM - 10:06AM |
NG.00008: The evolution of jet quenching form RHIC to the highest LHC energies Ivan Vitev 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 for the first time in more than a decade 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-medium 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 SCETG is implemented to present predictions for inclusive hadron suppression in Pb+Pb collisions at the highest LHC energies of 5.1 ATeV and discuss the relative significance of cold and hot nuclear matter effects. [Preview Abstract] |
Saturday, October 31, 2015 10:06AM - 10:18AM |
NG.00009: ABSTRACT WITHDRAWN |
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