Discrepancy of in-medium nucleon--nucleon cross-section in different T-matrix representations.

In this paper, we study the in-medium nucleon-nucleon (NN) cross-section by using the Dirac-Breuckner-Hartree-Fock approximation (DBHF) with T-matrix project technique for determining the nucleon self-energy. By solving Thompson equation for different partial-wave states separately, we find that the discrepancies of nucleon self-energies in various T-matrix project representations are dominated by the channels with smaller angular momentum. Although the cross-section is independent on the project of T-matrix, the medium suppression of the cross-section in various T-matrix representations are apparently different due to the self-consistency of DBHF calculation involving effect mass of nucleon as an iterative parameter. Our results also show that the crosssections in the complete pseudovector (CPV) choices are larger than those obtained with both DBHF in the pseudosealar (PS) choice and nonrelativistic Brueckner-Hartre-Fock with three-body force (BHF+3BF), respectively. Further comparison shows that the neutron-proton (NP) cross-section within DBHF + PV approach, σNPPV, is approximately equal to and slightly larger than that evaluated with BHF+3BF, σNP3BF, while the neutron-neutron (NN) (or proton-proton (PP)) cross-section given by DBHF+PV method, σNNPV, being the closest to the cross-section calculated by using BHF without 3BF in the lower energy region. Additionally, the discrepancies of the in-medium nucleonnucleon differential cross-section induced by different representations of T-matrix in DBHF are discussed for nuclear matter with different densities. [ABSTRACT FROM AUTHOR]