Nucleon-nucleon momentum correlation function as a probe of the density distribution of valence neutron in neutron-rich nucleus

TL;DR

This study investigates how the density distribution of valence neutrons in neutron-rich nuclei affects nucleon-nucleon momentum correlations, revealing that extended neutron distributions weaken correlation strength and can diagnose exotic nuclear structures.

Contribution

It demonstrates that nucleon-nucleon momentum correlation functions are sensitive to valence neutron density distributions, providing a new method to probe exotic nuclear structures like skins and halos.

Findings

Extended valence neutron density weakens correlation functions.

Correlation functions can diagnose nuclear skin and halo structures.

Emission source size correlates with neutron distribution extension.

Abstract

Proton-neutron, neutron-neutron and proton-proton momentum correlation functions ($C_{pn}$, $C_{nn}$, $C_{pp}$) are systematically investigated for $^{15}$C and other C isotopes induced collisions at different entrance channel conditions within the framework of the isospin-dependent quantum molecular dynamics (IDQMD) model complemented by the CRAB (correlation after burner) computation code. $^{15}$C is a prime exotic nucleus candidate due to the weakly bound valence neutron coupling with closed-neutron shell nucleus $^{14}$C. In order to study density dependence of correlation function by removing the isospin effect, the initialized $^{15}$C projectiles are sampled from two kinds of density distribution from RMF model, in which the valence neutron of $^{15}$C is populated on both 1$d$5/2 and 2$s$1/2 states, respectively. The results show that the density distributions of valence neutron significantly influence nucleon-nucleon momentum correlation function at large impact parameter and high incident energy. The extended density distribution of valence neutron largely weakens the strength of correlation function. The size of emission source is extracted by fitting correlation function using Gaussian source method. The emission source size as well as the size of final state phase space is larger for projectiles sampling from more extended density distribution of valence neutron corresponding 2$s$1/2 state in RMF model. Therefore momentum correlation function can be considered as a potential valuable tool to diagnose the exotic nuclear structure such as skin and halo.