Charge radii and neutron correlations in helium halo nuclei

TL;DR

This paper investigates the charge radii and neutron correlations in helium halo nuclei, revealing how dineutron correlations, spin-orbit effects, and core swelling influence observed charge radius changes.

Contribution

It introduces a complex-energy configuration interaction approach to analyze neutron correlations and charge radii in helium halo nuclei, highlighting the interplay of multiple effects.

Findings

Decrease in charge radius from $^6$He to $^8$He explained by multiple effects

Distinct neutron angular correlations in $^6$He resonances compared to ground states

Identification of key factors affecting charge radii in halo nuclei

Abstract

Within the complex-energy configuration interaction framework, we study correlations of valence neutrons to explain the behavior of charge radii in the neutron halo nuclei $^{6,8}$He. We find that the experimentally observed decrease of the charge radius between $^6$He and $^8$He is caused by a subtle interplay between three effects: dineutron correlations, a spin-orbit contribution to the charge radius, and a core swelling effect. We demonstrate that two-neutron angular correlations in the $2^+_1$ resonance of $^6$He differ markedly from the ground-state correlations in $^{6,8}$He.