### Session 1WA: Workshop: Quantifying the Character of the sQGP

Chair: Richard Seto, University of California, Riverside, and Huan Huang, University of California, Los Angeles
Room: Jewett Ballroom FGH

 Thursday, October 23, 2008 8:30AM - 9:05AM 1WA.00001: Heavy Quarks and Quarkonia in Thermal ${\rm aAdS}_5$ Invited Speaker: Derek Teaney I review how heavy quarks loose energy in AdS/CFT. I further show how the quantum mechanics of a string in ${\rm aAdS}_5$ together with Kruskal structure of AdS black holes gives rise to the expected stochastic dynamics of a quasi-particle in a thermal bath. The Kruskal structure is needed to reproduce the dynamics of the quasi-particle on the Schwinger-Keldysh contour. After initially considering a particle at rest I extend the results to quarks moving with finite velocity. With the stochastic dynamics of a fast quark clarified, I compute the rate of induced photon bremsthralung associated with the fast heavy quark and compare the results to perturbation theory. Finally I compute the drag of heavy quarkonia in AdS/CFT and discuss the relevance of these results to heavy ion collisions. Thursday, October 23, 2008 9:05AM - 9:40AM 1WA.00002: Exploring the Lower Limits of Perfection Invited Speaker: William A. Zajc A fascinating dialectic has emerged between the observation of perfect liquid'' behavior by the RHIC sQGP [1], and the near-simultaneous conjecture of a fundamental bound on the ratio of viscosity to entropy density $\eta/s \geq 1/4\pi$ obtained by Kovtun, Son and Starinets (KSS) [2] via the AdS/CFT correspondence. While the existence of such a bound was anticipated by Danielewicz and Gyulassy based on simple quantum mechanical arguments [3], the possible connection to those conformal field theories with gravity duals studied by KSS and others makes the determination of the value of $\eta/s$ for the RHIC fluid particularly intriguing. This talk will consider various approaches utilizing flow, fluctuations, heavy quark transport and detailed second-order causal hydrodynamic simulations. The self- consistency, or lack thereof, of the resulting values for $\eta/s$ will be discussed, along with prospects for future improved measurements and theoretical analysis.\\ \parindent=0pt \textbf{References}\\ \parindent=0pt [1] http://www.bnl.gov/bnlweb/pubaf/pr/PR\_display.asp?prID=05- 38 \\ \parindent=0pt [2] P.~Kovtun, D.T.~Son and A.O.~Starinets, Phys.~Rev.~Lett. {\bf 94}, 111601 (2005) [arXiv:hep-th/0405231]. \\ \parindent=0pt [3] P.~Danielewicz and M.~Gyulassy, Phys.~Rev.~ {\bf D31}, 53 (1985). Thursday, October 23, 2008 9:40AM - 10:15AM 1WA.00003: Quantifying dynamical QCD plasma through jet energy loss Invited Speaker: Magdalena Djordjevic In order to make reliable quantitative predictions for jet quenching in ultra-relativistic heavy ion collisions, it is necessary to have accurate calculations of energy loss. However, all currently available radiative heavy flavor energy loss studies suffer from a crucial drawback, which is an assumption that a medium is composed of static scattering centers. Since in reality the constituents of the medium are dynamical, it is necessary to include effects of dynamically screened QCD medium in order to obtain reliable theoretical predictions for jet quenching. We calculate, to first order in the number of scattering centers, the energy loss of a heavy quark traveling through a QCD medium consisting of dynamical constituents. We show that the result for a dynamical medium is significantly larger compared to a medium consisting of randomly distributed static scattering centers. Therefore, a quantitative description of jet suppression in RHIC and LHC experiments must correctly account for the dynamics of the medium's constituents. Thursday, October 23, 2008 10:15AM - 10:40AM 1WA.00004: COFFEE BREAK Thursday, October 23, 2008 10:40AM - 11:15AM 1WA.00005: Viscosity and heavy ion collisions Invited Speaker: Denes Molnar I will first review the essential ingredients of causal viscous hydrodynamics. The region of validity of the approach will be discussed based on comparison with nonequilibrium transport theory near the hydrodynamic regime. Then I will present calculations that show the influence of a small shear viscosity on heavy-ion observables at RHIC, mainly elliptic flow and spectra of light hadrons. These results will be used to estimate the shear viscosity of hot quark-gluon matter at RHIC. The effects of bulk viscosity will also be discussed. Thursday, October 23, 2008 11:15AM - 11:50AM 1WA.00006: Full jet-reconstruction in Au+Au collisions at RHIC Invited Speaker: Joern Putschke Measurements of inclusive hadron suppression and di-hadron azimuthal correlations in ultra-relativistic nuclear collisions have provided important insights into jet quenching in hot QCD matter, but are limited in their sensitivity due to well-known biases. Complete jet reconstruction in heavy-ion collisions would provide a direct measurement of the energy of the scattered parton before energy loss, alleviating such biases and allowing a measurement of the energy loss probability distribution necessary to extract properties of the medium in a model-independent way from hard probes. Recently at RHIC the first measurements of fully reconstructed jets in heavy-ion collisions were performed. Comparison of the jet energy spectra and the fragmentation function in Au+Au collisions to p+p reference measurements will be presented and discussed. Thursday, October 23, 2008 11:50AM - 12:25PM 1WA.00007: What we may learn from a beam energy scan at RHIC Invited Speaker: Paul Sorensen Recent measurements at RHIC reveal correlations unique to Heavy- ion collisions that exhibit an abrupt transition with energy. In this talk I discuss scenarios that may account for these correlation structures. I discuss what can be learned from the beam energy dependence of these structures and argue that performing a beam energy scan at RHIC will provide an unprecedented opportunity for discovery.