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

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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.