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

摘要

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 cross-sections in the complete pseudovector (CPV) choices are larger than those obtained with both DBHF in the pseudoscalar (PS) choice and nonrelativistic Brueckner-Hartree-Fock with three-body force (BHF + 3BF), respectively. Further comparison shows that the neutron-proton (NP) cross-section within DBHF + PV approach, σ_(NP)~(PV), is approximately equal to and slightly larger than that evaluated with BHF + 3BF, σ_(NP)~(3BF), while the neutron-neutron (NN) (or proton-proton (PP)) cross-section given by DBHF + PV method, σ_(NN)~(PV), 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 nucleon-nucleon differential cross-section induced by different representations of T-matrix in DBHF are discussed for nuclear matter with different densities.