Ab-initio analysis of $\beta$-delayed proton emission in $^{11}$Be*

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 $1/2^+$ proton resonance in $^{11}$B using the no-core shell model with continuum (NCSMC). This timely calculation helps to resolve whether this large branching ratio is caused by unknown dark decay modes or an unobserved proton resonance.