Dependence of two-nucleon momentum densities on total pair momentum

TL;DR

This study calculates two-nucleon momentum distributions in helium isotopes, revealing how pair ratios depend on total momentum and providing insights for experimental knock-out processes.

Contribution

It introduces a detailed analysis of how two-nucleon momentum densities vary with total pair momentum using realistic wave functions.

Findings

pp pairs are less common than pn pairs at low total momentum

The pp to pn ratio increases with total momentum, approaching nuclear pair ratios

Results are relevant for interpreting two-nucleon knockout experiments

Abstract

Two-nucleon momentum distributions are calculated for the ground states of 3He and 4He as a function of the nucleons' relative and total momenta. We use variational Monte Carlo wave functions derived from a realistic Hamiltonian with two- and three-nucleon potentials. The momentum distribution of pp pairs is found to be much smaller than that of pn pairs for values of the relative momentum in the range (300--500) MeV/c and vanishing total momentum. However, as the total momentum increases to 400 MeV/c, the ratio of pp to pn pairs in this relative momentum range grows and approaches the limit 1/2 for 3He and 1/4 for 4He, corresponding to the ratio of pp to pn pairs in these nuclei. This behavior should be easily observable in two-nucleon knock-out processes, such as A(e,e'pN).