Pairing Correlations in halo Nuclei

TL;DR

This paper investigates pairing correlations in halo nuclei $^{6}$He and $^{11}$Li using a three-body model, revealing strong di-neutron correlations and surface concentration of neutron pairs, consistent with experimental data.

Contribution

It introduces a density-dependent contact interaction model to analyze neutron pairing and spatial structure in halo nuclei, providing new insights into di-neutron correlations.

Findings

Neutron pairs are strongly concentrated on the nuclear surface.

The model reproduces experimental dipole excitation data.

Small open angles indicate strong di-neutron correlations.

Abstract

Paring correlations in weakly bound halo nuclei $^{6}$He and $^{11}$Li are studied by using a three-body model with a density-dependent contact interaction. We investigate the spatial structure of two-neutron wave function in a Borromean nucleus $^{11}$Li.The behavior of the neutron pair at different densities is simulated by calculating the two-neutron wave function at several distances between the core nucleus $^9$Li and the center of mass of the two neutrons. With this representation, a strong concentration of the neutron pair on the nuclear surface is quantitatively established for neutron-rich nuclei. Dipole excitations in $^{6}$He and $^{11}$Li are also studied within the same three-body model and compared with experimental data. The small open angles between the two neutrons from the core are extracted empirically by the B(E1) sum rule together with the rms mass radii, indicating the strong di-neutron correlation in the halo nuclei.