D ec 2 00 5 Energy densities and equilibration in heavy ion collisions at √ s NN = 200 GeV with the quark - gluon string model

We study thermodynamic characteristica of ultra-relativistic Au+Au collisions at RHIC energy √ s N N = 200 GeV within the framework of a microscopic transport model, namely the quark-gluon string model (QGSM). The temporal evolution of the local energy density, transverse and longitudinal pressure and equilibration times are considered. In contrast to complete equilibration which is even in central reactions hardly achieved, pre-equilibrium stages with energy densities well above the critical energy density predicted by lattice QCD are established at short time scales. Corresponding energy density profiles at proper time τ = 1 fm/c compare well with hydrodynamical assumptions for initial energy density distributions.