ANALYSIS OF COLLECTIVE FLOW IN HIGH-ENERGY HEAVY-ION COLLISIONS IN THE RELATIVISTIC VUU APPROACH

We have calculated the collective flow for Ar+KCl collisions of 1200 M eV/A by using the relativistic Vlasov-Uehling-Uhlenbeck (VUU) equation based on the QHD-I model of Walecka. The sensitivity of flow characte rized by C(psi) and [P(x)(Y)] to mean field and in-medium NN scatterin g cross section is studied. It is found that the azimuthal correlation function C(psi) is reduced dramatically after inserting the collision term and then varies very slowly between NN cross sections from sigma = 10 mb to 55 mb and reaches the minimum at sigma = 35 mb, while the in-plane mean transverse momentum [P(x)(Y)] increases slowly all the w ay from sigma = 0 mb to 55 mb. The collective flow is very sensitive t o the momentum dependence (indicated by the effective mass m) of the mean field and less sensitive to the compression modulus K and the cro ss sections from or = 10 mb to 55 mb. The numerical results were compa red with the experimental data, and we found that the agreement for bo th [P(x)(Y)] and C(psi) can be reached with the same set of mean field parameters as well as the appropriate NN cross section in collision t erms.