Issue Eur. Phys. J. C Volume 62, Number 1, July 2009 Hot Quarks 2008 Page(s) 63 - 68 Section Regular Article - Theoretical Physics DOI 10.1140/epjc/s10052-009-1000-8 Published online 08 April 2009

Eur. Phys. J. C 62, 63-68 (2009)
DOI: 10.1140/epjc/s10052-009-1000-8

Extracting hadronic viscosity from microscopic transport models

Nasser Demir and Steffen A. Bass

Department of Physics, Duke University, Durham, NC, 27708, USA

nsd5@phy.duke.edu

Received 20 October 2008 / Revised version 5 February 2009 / Published online 8 April 2009

Abstract

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 density ratio η/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 η/s. Such a rise in η/s would not be compatible with the success of (viscous) hydrodynamics, which requires a very small value of η/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 reduce the value of η/s, and argue that introduction of other chemical potentials could ensure the successful application of (viscous) hydrodynamics to collisions at RHIC.

PACS
25.75.Nq
51.20.+d

Correspondence: nsd5@phy.duke.edu


© Società Italiana di Fisica, Springer-Verlag 2009

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