We analyze the hadronic freeze-out in ultrarelativistic heavy-ion collisions at Relativistic Heavy Ion Collider (RHIC) in a transport approach that combines hydrodynamics for the early, dense, deconfined stage of the reaction with a microscopic nonequilibrium model for the later hadronic stage at which the hydrodynamic equilibrium assumptions are not valid. With this ansatz we are able to self-consistently calculate the freeze-out of the system and determine space-time hypersurfaces for individual hadron species. The space-time domains of the freeze-out for several hadron species are found to be actually four dimensional, and differ drastically for the individual hadrons species. Freeze-out radii distributions are similar in width for most hadron species, even though the ${\Omega }^{-}$ is found to be emitted rather close to the phase boundary and shows the smallest freeze-out radii and times among all baryon species. The total lifetime of the system does not change by more than 10% when going from CERN Super Proton Synchrotron to RHIC energies.

• Received 24 February 1999

DOI:https://doi.org/10.1103/PhysRevC.60.021902