arXiv:nucl-th/9907061·v1·Nuclear Theory
Microscopic study of freeze-out in relativistic heavy ion collisions at SPS energies
L.V. Bravina (1,2) · I.N. Mishustin (3,4,5) · J.P. Bondorf (3) · Amand Faessler (1) · E.E. Zabrodin (1,2) · ((1)- Institut fuer Theoretische Physik, Universitaet Tuebingen, Germany; (2)- Institute for Nuclear Physics, Moscow State University, Russia; (3)- The Niels Bohr Institute, Copenhagen, Denmark; (4)- The Kurchatov Institute, Russian Scientific Center, Moscow, Russia; (5)- Institut fuer Theoretische Physik, Universitaet Frankfurt, Germany)
Abstract
The freeze-out conditions in the light (S+S) and heavy (Pb+Pb) colliding systems of heavy nuclei at 160 AGeV/ are analyzed within the microscopic Quark Gluon String Model (QGSM). We found that even for the most heavy systems particle 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 volume of the reaction and reflect the main trends of the system evolution. Nucleons in Pb+Pb collisions initially come from the surface region. For both systems there is a separation of the elastic and inelastic freeze-out. The mesons with large transverse momenta, , are predominantly produced at the early stages of the reaction. The low -component is populated by mesons coming mainly from the decay of resonances. This explains naturally the decreasing source sizes with increasing , observed in HBT interferometry. Comparison with S+S and Au+Au systems at 11.6 AGeV/ is also presented.
Comments: REVTEX, 26 pages incl. 9 figures and 2 tables, to be published in the Physical Review C