New Investigation of Low-Lying States in Be12 Via a H2(B

We investigate the low-lying positive-parity states in $^{12}\mathrm{Be}$, which are populated by the $^{2}\mathrm{H}(^{13}\mathrm{B}$, $^{3}\mathrm{He})$ reaction via $l=1$ proton transfer for the first time using a radioactive beam $^{13}\mathrm{B}$ at 23 MeV/nucleon. Spectroscopic factors and excitation energies of these states are in reasonable agreement with the shell model predictions. Besides two bound states, we observe a resonant state at ${E}_{x}=4.8\phantom{\rule{0.16em}{0ex}}\ifmmode\pm\else\textpm\fi{}0.1\phantom{\rule{0.16em}{0ex}}\mathrm{MeV}$ with an intrinsic width of $0.42\ifmmode\pm\else\textpm\fi{}0.28$ MeV, which predominately decays via one neutron to the bound states in $^{11}\mathrm{Be}$. It most likely corresponds to the ${E}_{n}=1.24\phantom{\rule{0.16em}{0ex}}\mathrm{MeV}$ state observed in the previous one-proton removal reaction. The spin-parity of ${2}^{+}$ is tentatively assigned to this resonance according to the analysis of its angular distributions as well as the theoretical calculations, including shell model and Gamow coupled-channel approach.