Thermal Freeze-out and Longitudinally Non-uniform Collective Expansion Flow in Relativistic Heavy Ion Collisions

摘要

The non-uniform longitudinal flow model (NUFM) propsed recently is extendedto include also transverse flow. The resulting longitudinally non-uniformcollective expansion model (NUCEM) is applied to the calculation of rapiditydistribution of kaons, lambdas and protons in relativistic heavy ion collisionsat CERN-SPS energies. The model results are compared with the 200 A GeV/$c$ S-Sand 158 A GeV/$c$ Pb-Pb collision data. The central dips observed inexperiments are reproduced in a natural way.