Nucleon Effective E-Mass in Neutron-Rich Matter from the Migdal-Luttinger Jump

TL;DR

This paper constrains the nucleon effective E-mass in neutron-rich matter using the Migdal-Luttinger theorem and recent SRC experiments, revealing differences between neutrons and protons and their dependence on isospin asymmetry.

Contribution

It provides new quantitative constraints on the nucleon effective E-mass in symmetric and neutron-rich nuclear matter based on experimental data and theoretical analysis.

Findings

Effective E-mass in symmetric nuclear matter is approximately 2.22±0.35 times the nucleon mass.

Neutron E-mass is smaller than proton E-mass in neutron-rich matter.

Fermi sea depletion varies linearly with isospin asymmetry.

Abstract

The well-known Migdal-Luttinger theorem states that the jump of the single-nucleon momentum distribution at the Fermi surface is equal to the inverse of the nucleon effective E-mass. Recent experiments studying short-range correlations (SRC) in nuclei using electron-nucleus scatterings at the Jefferson National Laboratory (JLAB) together with model calculations constrained significantly the Migdal-Luttinger jump at saturation density of nuclear matter. We show that the corresponding nucleon effective E-mass is consequently constrained to $M_0^{\ast,\rm{E}}/M\approx2.22\pm0.35$ in symmetric nuclear matter (SNM) and the E-mass of neutrons is smaller than that of protons in neutron-rich matter. Moreover, the average depletion of the nucleon Fermi sea increases (decreases) approximately linearly with the isospin asymmetry $\delta$ according to $\kappa_{\rm{p}/\rm{n}}\approx 0.21\pm0.06 \pm (0.19\pm0.08)\delta$ for protons (neutrons). These results will help improve our knowledge about the space-time non-locality of the single-nucleon potential in neutron-rich nucleonic matter useful in both nuclear physics and astrophysics.