Updated three-body model of ${}^6$He ${\hat{I}}^2$ decay into the $\hat{I}\pm$ + $d$ continuum

Abstract

The ${\hat{I}}^2$-decay process of the ${}^6$He halo nucleus into the $\hat{I}\pm +d$ continuum is studied in an updated three-body model. The ${}^6$He nucleus is described as an $\hat{I}\pm +n+n$ system in hyperspherical coordinates on a Lagrange-mesh. The shape and absolute values of the transition probability per time and energy units of new experiments are reproduced with a modified $\hat{I}\pm +d$ potential. The obtained total transition probabilities are $2.48\times 10^{-6}$ s${}^{-1}$ for the full energy region and $2.40\times 10^{-6}$ s${}^{-1}$ for the cut-off $E>150$ keV. The strong cancellation between the internal and halo parts of the ${\hat{I}}^2$ decay matrix element is a challenge for future {\it ab initio} calculations.

4 pages, 3 figures