Medium Suppression of In medium Nucleon-Nucleon Cross Sections Predicted with Various Microscopic Calculations

The nucleon-nucleon cross sections in the dense nuclear matter are microscopically calculated by using Dirac- Brueckner-Hartree-Fock （DBHF） approximation with different covariant representations of the T-matrix, i.e., complete pseudo-vector （CPV）, pseudoscalar （PS） and pseudo-vector （PV） choices. Special attention is paid to the discrepancies among the cross sections calculated with these different T-matrix project choices. The results show that the medium suppression of the cross section given by DBHF in the CPV choice is not only smaller than those obtained in both PS and PV choices, but also smaller than the predictions with a nonrelativistic Brueckner-Hartree-Fock （BHF） method including three body force （3BF）. The further analysis reveals that the influence of the different choices on the cross section in the DBHF approximation is mainly determined by the state of smaller total angular momentum due to the medium effect being strongly suppressed in the higher angular momentum.