Dependence of self-energy components and cross sections of nucleons in-medium on the relative momentum of nucleons in nuclear matter from different projections choices of invariant amplitudes is studied within the framework of Dirac-Brueckner-Hartree-Fock model. Special attention is paid to the discrepancy between the self-energies and cross sections for different choices in various separate chances. Our results indicate that the self-energy of nucleons in the states with spin S = 1 and isospin triplets T = 1 is larger than those with S = 0 and T = 0 at a specified relative momentum. The dependence of the self-energies of nucleons in various reaction channels on the pseudo-scalar (PS) choice are more pronounced than that on the complete pseudo vector (CPV) choice, which is mainly due to the states with smaller total momentum quantum numbers J . Results of the in-medium differential cross sections show that the difference between dσ/dΩfor the neutron-proton and neutron-neutron (or proton-proton) in various choices is larger for smaller relative momentum of nucleons and smaller scattering angles in mass center reference frame However, the total cross sectionσtotal in the CPV choice is always larger than that in the PS choice. All these discrepancies will disappear with increasing incident energy.%本文利用Dirac-Brueckner-Hartree-Fock方法，对不同散射道的核子在核物质中的相互作用进行了细致分析，重点分析了不变振幅的不同投影选择对核物质中核子自能和核子碰撞截面的影响.计算结果显示：1)在确定的核子动量下，自旋三重态所对应的自能总是大于自旋单态的自能；同位旋三重态所对应的自能大于同位旋单态的自能值.2)在完全赝矢(CPV)选择下，不同散射道的核子自能对于动量的依赖均明显弱于在赝标(PS)选择下的相应值，而这种差别主要来自于总角动量J较小的分波态.3)在核子相对动量较小时，两种不同选择所对应的核子微分截面较大.4)在确定的入射能量下，质心系中散射角较小时，不同选择下的微分截面差别较为明显.5)在低入射能区， CPV选择下所对应的微分截面大于PS下的微分截面值.6)在CPV选择下的总截面总是大于PS选择下的总截面值.这些差别均随着随入射能量的增大而消失.
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