Equation of state, radial flow, and freeze-out in high energy heavy ion collisions

Abstract

We have shown that recent experimental data on radial flow, both from AGS and SPS energies, are in agreement with the equation of state (EOS) including the QCD phase transition. A new hydrokinetic model (HKM) is developed, which incorporates a hydrodynamical treatment of the expansion and proper kinetics of the freeze-out. We show that the freeze-out surfaces for different secondaries and different collisions are very different, and they are not at all isotherms $T$=const (as was assumed in most previous hydrodynamics works). Comparison of HKM results with the cascade-based event generator RQMD is also made in some detail: we found that both the EOS and flow are in rather good agreement, while the space-time picture is still somewhat different.