Direct photons from Au+Au collisions at RHIC: QGP vs. hot hadronic gas

Abstract

We have analysed the preliminary PHENIX data on the transverse momentum distribution of direct photons in 0-20% centrality Au+Au collisions at $\sqrt{s_{NN}}$=200 GeV. In ideal hydrodynamics, data are explained if Au+Au collision produces Quark-Gluon-Plasma at the temperature $T_i$=400 MeV, at an initial time ${\tau }_i$=0.6 fm. PHENIX data are not explained in the alternate scenario when Au+Au collisions produces hot hadronic gas with initial temperature within physically acceptable limit.

Comments: 4 pages, 2 figures