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.