Experimental study of the $^{11}\text{B}(p,3\alpha)\gamma$ reaction at $E_p = 0.5-2.7$ MeV

Abstract

Our understanding of the low-lying resonance structure in $^{12}$C remains incomplete. We have used the $^{11}\text{B}(p,3\alpha)\gamma$ reaction at proton energies of $E_p=0.5-2.7$ MeV as a selective probe of the excitation region above the $3\alpha$ threshold in $^{12}$C. Transitions to individual levels in $^{12}$C were identified by measuring the 3$\alpha$ final state with a compact array of charged-particle detectors. Previously identified transitions to narrow levels were confirmed and new transitions to broader levels were observed for the first time. Here, we report cross sections, deduce partial $\gamma$-decay widths and discuss the relative importance of direct and resonant capture mechanisms.