Neutron skins probed in proton knockout from neutron-rich nuclei

TL;DR

This paper develops a unified theoretical framework for proton knockout reactions to probe neutron skins in neutron-rich nuclei, revealing systematic sensitivities of reaction observables to neutron-skin thickness and nuclear symmetry energy.

Contribution

It introduces a probabilistic Glauber-based model combined with microscopic densities to analyze (p,2p) and (p,3p) reactions, highlighting their sensitivity to neutron skins.

Findings

Cross sections decrease with increasing neutron excess.

Momentum dispersions are sensitive to neutron-skin thickness.

Two-proton removal reactions show stronger sensitivity to neutron skins.

Abstract

Proton-induced quasifree knockout reactions provide a powerful probe of nuclear single-particle structure and reaction dynamics in both stable and neutron-rich nuclei. In this work we develop a unified theoretical framework for the calculation of inclusive (p,2p) and sequential (p,3p) reaction cross sections and fragment momentum distributions at intermediate and relativistic energies. The approach is based on a probabilistic extension of Glauber multiple-scattering theory combined with microscopic nuclear densities obtained from Hartree-Fock-Bogoliubov calculations using Skyrme energy-density functionals. We focus in particular on the sensitivity of total cross sections and longitudinal momentum dispersions to neutron-skin thickness along isotopic chains. Our results indicate that both (p,2p) and (p,3p) reactions exhibit a systematic decrease of cross section and momentum width with increasing neutron excess, reflecting enhanced attenuation and surface bias induced by neutron skins. The effect is significantly stronger for two-proton removal, suggesting that (p,3p) reactions may offer enhanced sensitivity to isovector nuclear structure. These findings establish proton-induced knockout reactions as complementary hadronic probes of neutron skins and the density dependence of the nuclear symmetry energy.