Stylized features of single-nucleon momentum distributions

TL;DR

This paper introduces a practical method to compute short-range correlation contributions to high-momentum parts of single-nucleon momentum distributions, explaining the dominance of proton-neutron pairs and their mass dependence.

Contribution

The work presents a low-order operator expansion method applicable across the nuclear chart, improving mean-field models by incorporating SRC effects into operators rather than wave functions.

Findings

The model reproduces the high-momentum tail of momentum distributions.

It explains the dominance of proton-neutron pairs in SRC.

Predicts the ratio of proton-proton to proton-neutron correlated pairs.

Abstract

Nuclear short-range correlations (SRC) typically manifest themselves in the tail parts of the single-nucleon momentum distributions. We propose an approximate practical method for computing those SRC contributions to the high-momentum parts. The framework adopted in this work is applicable throughout the nuclear mass table and corrects mean-field models for central, spin-isospin and tensor correlations by shifting the complexity induced by the SRC from the wave functions to the operators. It is argued that the expansion of these modified operators can be truncated to a low order. The proposed model can generate the SRC-related high-momentum tail of the single-nucleon momentum distribution. These are dominated by correlation operators acting on mean-field pairs with vanishing relative radial and angular-momentum quantum numbers. The proposed method explains the dominant role of proton-neutron pairs in generating the SRC and accounts for the magnitude and mass dependence of SRC as probed in inclusive electron scattering. It also provides predictions for the ratio of the amount of correlated proton-proton to proton-neutron pairs which are in line with the observations. In asymmetric nuclei, the correlations make the average kinetic energy for the minority nucleons larger than for the majority nucleons.