Chemical freeze-out parameters at RHIC from microscopic model calculations

Abstract

The relaxation of hot nuclear matter to an equilibrated state in the central zone of heavy-ion collisions at energies from AGS to RHIC is studied within the microscopic UrQMD model. It is found that the system reaches the (quasi)equilibrium stage for the period of 10-15 fm/$c$. Within this time the matter in the cell expands nearly isentropically with the entropy to baryon ratio $S/A=150-170$. Thermodynamic characteristics of the system at AGS and at SPS energies at the endpoints of this stage are very close to the parameters of chemical and thermal freeze-out extracted from the thermal fit to experimental data. Predictions are made for the full RHIC energy $\sqrt{s}=200$ AGeV. The formation of a resonance-rich state at RHIC energies is discussed.

Talk at the conference Quark Matter'2001, 4 pages, to appear in Nucl. Phys. A