IN-MEDIUM CROSS SECTIONS IN DIRAC-BRUECKNER-HARTREE-FOCK APPROACH

Abstract

The transport models, which are employed to describe the central reactions in heavy ion collisions(HIC), are powerful approaches to reproduce the collective observable in HIC and probe the equation of state(EOS) of nuclear matter. Those models, such as the quantum molecular dynamics (QMD) and Boltzmann-UehlingUhlenbeck (BUU) equation as well as their relativistic extensions (RBUU and RQMD), treat the nucleon mean fields and nucleon-nucleon scattering cross sections as the basic input ingredients. Up to now, most caculations of particle producing in nucleus-nucleus reaction are using the free cross sections or the approximations σ∗ NN = 0.8σ free NN , σ ∗ NN/σ free NN = (m ∗/m)2 instead of the in-medium cross sections. Many recent papers have devoted to the in-medium N-N scattering problem within different methods, such as the collectivistic Brueckner approach, and Dirac-Brueckner-Hartree-Fock(DBHF) approach. Here we apply the DBHF approach for its successfully describing the mechanism of the EOS, which meets the empirical region of saturation. However, because of the uncertainty in determining the nucleon self-energy in DBHF approach, Horowitz and Serot have developed a projection technique in which projects the G-matrix onto five covariant amplitudes. This set of five covariant amplitudes is not unique, corresponding to different representations, and we adopt two different representations (pseudo-scalar(ps) and complete pseudo-vector(pv) representations).