Direct photon observables from hydrodynamics and implications on the initial temperature and EoS

Research output: Contribution to journalConference article


The expansion of the strongly interacting quark gluon plasma (sQGP) created in Au+Au colli-sions at RHIC can be described by hydrodynamical models. Hadrons are created after a freeze-out, thus their distribution describes the final state of the evolution. The earlier stages can be analyzed via penetrating probes like photon observables. These were measured in 2010 and 2011 by the PHENIX experiment. Here we analyze an analytic, 1+3 dimensional perfect relativistic hydrodynamic solution and calculate hadron and photon observables, such as transverse momen-tum spectra, elliptic flow and correlation (HBT) radii. We find that our model is not incompatible with the data, not even with the direct photon elliptic flow. From fitting the data, we find that early temperatures of the sQGP were well above the quark-hadron transition temperature, in the hottest point, the center of the fireball the temperature may have reached 507±12 MeV. The equation of state of this quark matter can be described by an average speed of sound of 0.36±0.02. We also predict a photon source that is significantly larger in the out direction than in the side direction.

Original languageEnglish
Article number035
JournalProceedings of Science
Publication statusPublished - Jan 1 2011
Event7th Workshop on Particle Correlations and Femtoscopy, WPCF 2011 - Tokyo, Japan
Duration: Sep 20 2011Sep 24 2011


ASJC Scopus subject areas

  • General

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