Eur. Phys. J. C 71, 1510 (2011)
https://doi.org/10.1140/epjc/s10052-010-1510-4

Percolation of color sources and the equation of state of QGP in central Au–Au collisions at √s_NN = 200 GeV

Department of Physics, Purdue University, West Lafayette, IN, 47907, USA

brijesh@purdue.edu

Received: 10 August 2010
Revised: 29 September 2010
Published online: 20 January 2011

Abstract

The Color String Percolation Model (CSPM) is used to determine the equation of state (EOS) of the Quark–Gluon Plasma (QGP) produced in central Au–Au collisions at  A GeV using STAR data at RHIC. When the initial density of interacting colored strings exceeds the 2D percolation threshold a cluster is formed, which defines the onset of color deconfinement. These interactions also produce fluctuations in the string tension which transforms the Schwinger particle (gluon) production mechanism into a maximum entropy thermal distribution analogous to QCD Hawking–Unruh radiation. The single string tension is determined by identifying the known value of the universal hadron limiting temperature T _c =167.7±2.6 MeV with the CSPM temperature at the critical percolation threshold parameter ξ _c =1.2. At midrapidity the initial Bjorken energy density and the initial temperature determine the number of degrees of freedom consistent with the formation of a ∼2+1 flavor QGP. An analytic expression for the equation of state, the sound velocity is obtained in CSPM. The CSPM and the bulk thermodynamic values energy density ε/T ⁴ and entropy density s/T ³ are in excellent agreement in the phase transition region with recent lattice QCD simulations (LQCD) by the HotQCD Collaboration.