Strong dineutron correlation in 8He and 18C

TL;DR

This study reveals strong dineutron correlations in the surface region of $^8$He and $^{18}$C nuclei using a core+4n model with HFB approximation, highlighting the importance of neutron pairing in these neutron-rich systems.

Contribution

The paper introduces a detailed HFB-based analysis of dineutron correlations in $^8$He and $^{18}$C, providing new insights into their ground state structures.

Findings

Strong dineutron correlations are observed around the nuclear surface.

The ground state wave function of $^8$He significantly deviates from a pure (1p$_{3/2})^4$ configuration.

Probabilities of specific neutron configurations are quantified, aligning with recent experimental data.

Abstract

We study the spatial structure of four valence neutrons in the ground state of $^8$He and $^{18}$C nuclei using a core+4$n$ model. For this purpose, we employ a density-dependent contact interaction among the valence neutrons, and solve the five-body Hamiltonian in the Hartree-Fock-Bogoliubov (HFB) approximation. We show that two neutrons with the coupled spin of $S$=0 exhibit a strong dineutron correlation around the surface of these nuclei, whereas the correlation between the two dineutrons is much weaker. Our calculation indicates that the probability of the (1p$_{3/2})^4$ and [(1p$_{3/2})^2$ (p$_{1/2})^2$] configurations in the ground state wave function of $^8$He nucleus is 34.9% and 23.7%, respectively. This is consistent with the recent experimental finding with the $^8$He($p,t)^6$He reaction, that is, the ground state wave function of $^8$He deviates significantly from the pure (1p$_{3/2})^4$ structure.