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 MeV/A by using the relativistic Vlasov-Uehling- Uhlenbeck (VUU) equation based on the QHD-I model of Walecka. The tensitivity of flow characterized by C(ψ)a nd (P_x(Y))to mean field and in-medium NN scattering cross section is studied. It is found that the azimuthal correlation function C(ψ) is reduced dramatically after inserting the collision term and then varies very slowly between NN cross sections from σ = 10 mb to 55 mb and reaches the minimum at σ = 35 mb, while the in-plane mean transverse momentum (P_x(Y))in creases slowly all the way from σ = 0 mb to 55 mb. The collective flow is very sensitive to the momentum dependence (indicated by the effective mass m⁰) of the mean field and less sensitive to the compression modulus K and the cross sections from σ = 10 mb to 55 mb. The numerical results were compared with the experimental data, and we found that the agreement for both (P_x(Y)) and C(ψ) can be reached with the same set of mean field parameters as well as the appropriate NN cross section in collision terms.