Direct observation of proton emission in 11Be

Abstract

The elusive $β^-\text{p}^+$ decay was observed in ${}^{11}$Be by directly measuring the emitted protons and their energy distribution for the first time with the prototype Active Target Time Projection Chamber (pAT-TPC) in an experiment performed at ISAC-TRIUMF. The measured $β^-\text{p}^+$ branching ratio is orders of magnitude larger than any previous theoretical model predicted. This can be explained by the presence of a narrow resonance in ${}^{11}$B above the proton separation energy.