Electromagnetic and weak processes with light halo nuclei

TL;DR

This paper models electromagnetic and weak processes in light halo nuclei, specifically 6He and 6Li, using a three-body approach to match experimental data and analyze halo effects and charge symmetry.

Contribution

It introduces a three-body model for halo nuclei that accurately reproduces beta-decay and M1-transition probabilities, highlighting the importance of halo structures and phase shift sensitivities.

Findings

Beta-decay probability matches experimental data.

Halo effects significantly influence transition matrix elements.

Charge symmetry is confirmed through process comparison.

Abstract

The beta-decay of the 6He halo nucleus and the M1-transition processes of the excited 6Li(0+) state into the alpha + d continuum are studied in a three-body model. The initial nuclear states are described as an alpha + 2N system in hyperspherical coordinates on a Lagrange mesh. The energy dependence and absolute values of the beta-transition probability per time and energy units of a recent experiment can be reproduced very well with an appropriate alpha + d potential. A total transition probability of 2.04E-6 s^(-1) is obtained in agreement with the experiment. Due to a strong cancellation of the internal and halo components of the matrix elements, halo effects are shown to be very important. For the M1 transition process the halo structure of the excited 6Li(0+) isobaric analog state is confirmed. The cancellation effects, however, are not so strong. The transition probability is strongly sensitive to the description of the alpha + d phase shifts. Charge symmetry is analyzed through a comparison of the two processes. The present branching ratio Gamma(0^+ --> alpha + d)/Gamma(0^+ --> 1+) is of the order 1.0E-4, and is expected to be observable in current experiments.