Universality of nucleon-nucleon short-range correlations: two-nucleon momentum distributions in few-body systems

TL;DR

This paper investigates the universality of short-range correlations in nucleon pairs within light nuclei, demonstrating that two-nucleon momentum distributions exhibit universal features consistent with SRC models, and predicts observable signatures in knock-out experiments.

Contribution

It provides a detailed analysis of two- and three-nucleon short-range correlations in light nuclei using realistic wave functions, highlighting universal behaviors and angular dependencies.

Findings

At high relative momenta, distributions are angle independent and factorize into deuteron distributions and a decreasing function of $K_{CM}$.

Distributions show strong angle dependence when both $K_{CM}$ and $k_{rel}$ are large, indicating three-nucleon SRC.

Predicted dependencies should be observable in two-nucleon knock-out experiments.

Abstract

Using realistic wave functions, the proton-neutron and proton-proton momentum distributions in $^3He$ and $^4He$ are calculated as a function of the relative, $k_{rel}$, and center of mass, $K_{CM}$, momenta, and the angle between them. For large values of ${k}_{rel}\gtrsim 2\,\,fm^{-1}$ and small values of ${K}_{CM} \lesssim 1.0\,\,fm^{-1}$, both distributions are angle independent and decrease with increasing $K_{CM}$, with the $pn$ distribution factorizing into the deuteron momentum distribution times a rapidly decreasing function of $K_{CM}$, in agreement with the two-nucleon (2N) short range correlation (SRC) picture. When $K_{CM}$ and $k_{rel}$ are both large, the distributions exhibit a strong angle dependence, which is evidence of three-nucleon (3N) SRC. The predicted center-of-mass and angular dependence of 2N and 3N SRC should be observable in two-nucleon knock-out processes $A(e,e'pN)X$.