Effective Nucleon Masses in Symmetric and Asymmetric Nuclear Matter

Abstract

The momentum and isospin dependence of the in-medium nucleon mass are studied. Two definitions of the effective mass, i.e. the Dirac mass $m_D^{\ast }$ and the nonrelativistic mass $m_{NR}^{\ast }$ which parameterizes the energy spectrum, are compared. Both masses are determined from relativistic Dirac-Brueckner-Hartree-Fock calculations. The nonrelativistic mass shows a distinct peak around the Fermi momentum. The proton-neutron mass splitting in isospin asymmetric matter is $m_{D,n}^{\ast }<m_{D,p}^{\ast }$ and opposite for the nonrelativistic mass, i.e. $m_{NR,n}^{\ast }>m_{NR,p}^{\ast }$, which is consistent with nonrelativistic approaches.

Comments: 11 pages, 4 figures, minor changes, to appear in Physical Review Letters