Microscopic study of freeze-out in relativistic heavy-ion collisions at 160A GeV/c energy - art. no. 044905

The freeze-out conditions in the light (S+S) and heavy (Pb+Pb) colliding sy stems of heavy nuclei at 160A GeV/c are analyzed within the microscopic qua rk-gluon string model. We found that even for the most heavy systems partic le emission takes place from the whole space-time domain available for the system evolution, but not from the thin "freeze-out hypersurface," adopted in fluid dynamical models. Pions are continuously emitted from the whole vo lume of the reaction and reflect the main trends of the system evolution. N ucleons in Pb+Pb collisions initially come from the surface region. For bot h systems there is a separation of the elastic and inelastic freeze-out. Th e mesons with large transverse momenta p(t) are predominantly produced at t he early stages of the reaction. The low p(t) component is populated by mes ons coming mainly from the decay of resonances. This explains naturally the decreasing source sizes with increasing p(t), observed in Hanbury-Brown-Tw iss interferometry. Comparison with S+S and Au+Au systems at 11.6A GeV/c is also presented. [S0556-2813(99)01310-2].