Evidence of a near-threshold resonance in ${}^{11}$B relevant to the $\beta$-delayed proton emission of ${}^{11}$Be

Abstract

A narrow near-threshold proton-emitting resonance (Ex = 11.4 MeV, J${}^{\pi }$ = 1/2${}^{+}$ and ${\Gamma }_p$ = 4.4 keV) was directly observed in ${}^{11}$B via proton resonance scattering. This resonance was previously inferred in the $\beta$-delayed proton emission of the neutron halo nucleus ${}^{11}$Be. The good agreement between both experimental results serves as a ground to confirm the existence of such exotic decay and the particular behavior of weakly bound nuclei coupled to the continuum. $R$-matrix analysis shows a sizable partial decay width for both, proton and $\alpha$ emission channels.