A Halo: The Trigger to a New Era of Nuclear Correlations

TL;DR

This paper explores halo phenomena in nuclei, focusing on the anti-halo effect, continuum coupling, and soft dipole excitations, highlighting the importance of advanced theoretical models in understanding nuclear halo structures.

Contribution

It demonstrates the significance of continuum-coupled Hartree-Fock-Bogoliubov theories in accurately describing halo effects and soft dipole excitations in deformed halo nuclei.

Findings

Anti-halo effect is highly sensitive to continuum coupling.

Continuum coupling largely cancels the anti-halo effect on neutron radius.

Soft dipole response peaks indicate halo effects and nuclear deformation.

Abstract

In this contribution to the Halo-40 Proceedings, we discuss two topics regarding halo phenomena: The first is the pairing anti-halo effect on the neutron radius of halo nuclei and its restoration due to the coupling to the continuum; the second is the soft dipole excitation of deformed halo nuclei. We demonstrate the importance of Hartree-Fock-Bogoliubov and the relativistic Hartree-Bogoliubov theory in continuum for properly taking into account the halo nature of extended wave functions in calculations of neutron radii, as well as the soft dipole excitations of halo nuclei. It was shown that the anti-halo effect is very sensitive to the continuum coupling induced by Bogoliubov-type quasi-particles, which largely cancels the anti-halo effect on the neutron radius. The soft dipole excitations of deformed halo nuclei Ne-31 and Mg-37 are discussed within the deformed Woods-Saxon model. We point out that the sharp peak just above the threshold in the dipole response is created by the halo effect, and its strength can be used to identify the magnitude of deformation and the halo configuration in the Nilsson level scheme.