Excitation Halo States of 12 B

Angular distributions for the 11B(d,p)12B transfer reactions have been measured at Elab = 11.8 MeV. The asymptotic normalization coefficients (ANC) of the ground state, the second and third excitation states for 12B (11B+n) are extracted from the differential cross sections at three forward angles. With these ANCs, the root-mean-square radii are calculated for these three states. The results show that the second and third excitation states of 12B are neutron halo states.