Ab initio calculation of the $\beta$-decay from ${}^{11}$Be to a p${+}^{10}$Be resonance

Abstract

The exotic $\beta$-delayed proton emission is calculated in ${}^{11}$Be from first principles using chiral two- and three-nucleon forces. To investigate the unexpectedly-large branching ratio measured in [PRL 123, 082501 (2019)] we calculate the proposed $(1/2^{+},1/2)$ proton resonance in ${}^{11}$B using the no-core shell model with continuum. This calculation helps to address whether this enhancement is caused by unknown dark decay modes or an unobserved proton resonance. We report a branching ratio of $b_p=(1.3\pm 0.5)\times 10^{-6}$, suggesting that its unexpectedly-large value is caused by an unobserved proton resonance in ${}^{11}$B.

Comments: 12 pages, 5 figures