Equation of state and initial temperature of quark gluon plasma at RHIC
Abstract
In goldgold collisions of the Relativistic Heavy Ion Collider a perfect fluid of strongly interacting quark gluon plasma (sQGP) is created. The time evolution of this fluid can be described by hydrodynamical models. After an expansion, hadrons are created during the freezeout period. Their distribution reveals information about the final state. To investigate the time evolution one needs to analyze penetrating probes: e.g. direct photon observations. In this paper we analyze a 1+3 dimensional solution of relativistic hydrodynamics. We calculate momentum distribution, azimuthal asymmetry and momentum correlations of direct photons. Based on earlier fits to hadronic spectra, we compare photon calculations to measurements to determine the equations of state and the initial temperature of sQGP. We find that the initial temperature in the center of the fireball is 507±12 MeV, while for the sound speed we get c _{ s }=0.36±0.02. We also estimate a systematic error of these results. We find that the measured azimuthal asymmetry is also compatible with this model. We also predict a photon source that is significantly larger in the out direction than in the side direction.
 Publication:

Central European Journal of Physics
 Pub Date:
 August 2012
 DOI:
 10.2478/s1153401200609
 arXiv:
 arXiv:1101.1279
 Bibcode:
 2012CEJPh..10..850C
 Keywords:

 hydrodynamics;
 quarkgluon plasma;
 direct photons;
 hydrodynamics;
 quarkgluon plasma;
 direct photons;
 Nuclear Theory
 EPrint:
 12 pages, 4 figures. This work was supported by the OTKA grant NK73143 and NK101438 and M. Csanad's Bolyai scholarship