Quark Matter 2005 Conference   Quark Matter 2005 Conference


What can we learn from hydrodynamic analysis of elliptic flow?

Presenting Author: Dr. Tetsufumi Hirano

Author(s): Tetsufumi Hirano, Miklos Gyulassy

Abstract:

The agreement of hydrodynamic results of radial and elliptic flow patterns with Au+Au data at RHIC is the main evidence suggesting the nearly perfect fluidity of the strongly coupled Quark Gluon Plasma, sQGP. We study the sensitivity of this conclusion to different hydrodynamic assumptions on chemical and thermal freezeout. If chemical freezeout occurs at the hadronization time to reproduce the hadron yields, $v_2(p_T)$ continues to increase with proper time in the hadronic phase and leads to a discrepancy with the data. This counter intuitive effect arises due to the decrease of the mean pion transverse momentum $$. In contrast, if both chemical and thermal equilibrium are maintained in the hadron phase, $v_2(p_T)$ pattern is preserved due to the increase of $$, which causes accidental reproduction of the data. In order that hadronic ratios, $p_T$ spectra, and $v_2(p_T)$ be reproduced, the sQGP must expand with a less viscosity than the hadronic matter.


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