Modeling the breakup stage of relativistic heavy-ion collisions

By using the output of a thermal model as the input to a hadronic cascade, we investigate the role of kinetic and chemical equilibrium in the breakup stage of 158A GeV/c Pb+Pb collisions at CERN. Gross features of experimental pion and proton spectra are fit, as well as the transverse energy and baryons per unit rapidity. However, experimental source sizes extracted from pion correlations and the low p_t behavior of pion spectra are not reproduced. We argue that pionic phase space has become overpopulated compared to equilibrium considerations. Other issues regarding chemical and kinetic equilibration are also explored.