Bulletin of the American Physical Society
2008 Annual Meeting of the Division of Nuclear Physics
Volume 53, Number 12
Thursday–Sunday, October 23–26, 2008; Oakland, California
Session FF: Mini-Symposium: Viscosity, String Theory and Hydrodynamics |
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Chair: W.A. Zajc, Columbia University Room: Simmons Ballroom 4 |
Saturday, October 25, 2008 8:30AM - 9:06AM |
FF.00001: Hydrodynamics and gauge/gravity duality Invited Speaker: Recently gauge/gravity duality has been used to extract informations about the hydrodynamic behavior of strongly coupled systems. We will review the progress that has been made, and look at future directions. [Preview Abstract] |
Saturday, October 25, 2008 9:06AM - 9:18AM |
FF.00002: Shear Transport Coefficients from Gauge/Gravity Correspondence Joseph Kapusta, Todd Springer We study the shear mode in the gauge/gravity correspondence at finite temperature. First, we confirm the general formula for the shear viscosity in an arbitrary background metric which includes a black hole in the fifth dimension. We then derive a general formula for the shear mode relaxation time which appears in the theory of relativistic dissipative fluid dynamics; it agrees with known expressions in the limit of conformal fields. These results may be useful in relativistic viscous fluid descriptions of high energy nuclear collisions at RHIC and LHC. [Preview Abstract] |
Saturday, October 25, 2008 9:18AM - 9:30AM |
FF.00003: The Lattice QCD Equation of State and Implications for Hydrodynamic Modeling of Heavy Ion Collisions Ron Soltz We present results for the QCD Equation of State of at zero baryon density calculated on a lattice of dimensions $32^3 \times 8$ with $m_l = 0.1 m_s$ using two improved staggered fermion actions, p4 and asqtad. Calculations were performed along lines of constant physics with a pion mass of approximately 200~MeV, and were carried out using more than 100M cpu-hours on BG/L supercomputers at LLNL, BNL, and UCSD. Both calculations are consistent with a cross-over transition in the range 185 -- 195~MeV/c. Recent results from the lattice will be compared to those currently used as input to hydrodynamic models. Consequences for calculations of observables such as spectra, flow, and space-time measurements in heavy ion collisions will be discussed. [Preview Abstract] |
Saturday, October 25, 2008 9:30AM - 9:42AM |
FF.00004: Measurements of High $p_{T}$ Identified Hadron $v_{2}$ in Au+Au Collisions at $\sqrt{S_{NN}}$ = 200 GeV by the PHENIX Experiment Shengli Huang Measurements of the elliptic flow $v_{2}$ at RHIC have provided sensitive information about the earliest stages dynamics of heavy ion collisions. The $v_{2}$ of identified hadrons has been found empirically to scale with the number of constituent quarks at low $p_{T}$, providing evidence that partonic degrees of freedom determine the early dynamics of the system. The measurement of high $p_{T}$ identified hadrons $v_{2}$ will allow us to further test this scaling. It will provide the information on the limits of applicability of the hydrodynamic description of the system dynamics. The difference of $v_{2}$ between the $K^{+}$, $K^{-}$ and the proton, anti-proton at high $p_{T}$ will also provide the information about the particle production and dynamics mechanism. In that the $K^{-}$ and anti-proton are mainly from gluon fragmentation, while the $K^{+}$ and proton are mainly from light quark fragmentation. In this talk, we will present measurements of pion, kaon and proton $v_{2}$ to $p_T$ of 6GeV/c as a function of centrality in Au + Au collisions at $\sqrt{S_{NN}}$ = 200 GeV. The constituent quark scaling will be tested by these new measurements in the different centrality bins. The $v_{2}$ difference between the $K^{+}$ , $K^{-}$ and the proton, anti-proton will also be studied as a function of $p_{T}$ and centrality. [Preview Abstract] |
Saturday, October 25, 2008 9:42AM - 9:54AM |
FF.00005: Influence of Finite Chemical Potential on Hadronic Shear Viscosity Nasser Demir, Steffen A. Bass Ultrarelativistic heavy-ion collisions at the Relativistic Heavy-Ion Collider (RHIC) are thought to have created a Quark-Gluon-Plasma, characterized by a very small shear viscosity to entropy ratio $\eta/s$, close to the lower bound predicted for that quantity by string theory. However, due to the dynamics of the collision, the produced matter passes through a phase characterized by an expanding and rapidly cooling hadron gas with strongly increasing viscosity to entropy ratio. Such a rise in $\eta/s$ would not be compatible with the success of (viscous) hydrodynamics, which requires a very small value of $\eta/s$ throughout the full evolution of the reaction in order to successfully describe the collective flow seen in the experiments. Here we show that the inclusion of a pion chemical potential, which is bound to arise due to the separation of chemical and kinetic freeze-out during the collision evolution, will keep the value of $\eta/s$ sufficiently small to ensure the successful application of (viscous) hydrodynamics to collisions at RHIC. [Preview Abstract] |
Saturday, October 25, 2008 9:54AM - 10:06AM |
FF.00006: Propagating Mach Cones in a Viscous Quark-Gluon Plasma R. Bryon Neufeld I will discuss the space-time distribution of energy and momentum deposited by a fast parton traversing a perturbative quark-gluon plasma (arXiv:0805.0385 [hep-ph]). I use this distribution as a source term for the linearized hydrodynamical equations of the medium and present the resulting dynamics for three different values of the shear viscosity to entropy density ratio, $\eta/s$: $1/4\pi$, $3/4\pi$ and $6/4\pi$. I show that well defined Mach cones are found for $\eta/s = 1/4\pi, 3/4\pi$ but the conical structure begins to smear out for $\eta/s = 6/4\pi$. [Preview Abstract] |
Saturday, October 25, 2008 10:06AM - 10:18AM |
FF.00007: Unveiling properties of the QGP with Multi-Particle Correlations from the PHENIX Experiment Nuggehalli Ajitanand There is ample evidence to suggest that in heavy ion collisions at RHIC a strongly interacting state of matter resembling a near-perfect liquid (termed sQGP) is formed. It is conjectured that jet interactions can excite Mach-cone-like features in such a medium. In this study we present results of multi-particle correlations from the PHENIX experiment which are capable of discerning the presence of such exotic in-medium effects. In particular, details of three-particle correlation studies and the estimates of the sound speed that they provide, will be presented. Finally, the special case of these correlations when one of the particles is constrained by the reaction plane, will be discussed. [Preview Abstract] |
Saturday, October 25, 2008 10:18AM - 10:30AM |
FF.00008: Quest for the Degrees of Freedom in sQGP: An Electric-Magnetic Duality Perspective Jinfeng Liao, Edward Shuryak Based on monopoles and generic E-M duality, we have recently suggested a ``magnetic scenario'' [PRC75:054907,2007] for quark-gluon plasma in 1-2$T_c$ region (known as sQGP) --- a plasma in which monopoles become light, weakly coupled, and dominant d.o.f near $T_c$, while electric particles (quarks and gluons) are forced to become heavy and strongly coupled, eventually confined. This picture has been supported by several independent lattice results. In particular our ``magnetic scenario'' predicted that electric/magnetic effective coupling should run in opposite direction as temperature changes. This was confirmed in our paper [arXiv:0804.0255[hep-ph]] by analyzing recent accurate data about lattice monopoles. As applications of the ``magnetic scenario'', we were able to show: (1) a strongly coupled plasma with equally mixed electric and magnetic charges has the desired transport properties very close to the ``perfect liquid'' observed at RHIC; (2) the dense monopole plasma at $T=(0.8-1.3)T_c$ could support metastable flux tubes between $\bar Q Q$ and allow us to explain the non-trivial $T$-dependence of the static $\bar Q Q$ potentials calculated on the lattice, see [Phys. Rev. C 77: 064905, 2008] and [arXiv:0804.4890 [hep-ph]]. [Preview Abstract] |
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