Triplet ¹²B–¹²C–¹²N: Search for States with Halo

Abstract

Previously in [1] neutron halo was confirmed for the 2¯, 1.67 MeV and 1¯, 2.62 MeV states in 12 B on base of Asymptotic Normalization Coefficients (ANC) method analysis of the obtained experimental data. An unexpected result was received for the unbound 3¯, 3.39 MeV state. Its halo radius was found to be increased and equal to ~ 5.9 fm. This result can be considered as an evidence of the halo-like structure in this 12 B state. It should be noted that last neutron in this state has a non-zero orbital momentum (l=2). So question arises about possible existence of states with halo in other members of the isobaric triplet 12 B-12 C-12 N. We can expect the formation of a proton halo in the 2¯, 1.19 MeV and 1¯, 1.80 MeV states of 12 N and 2¯, 16.62 MeV and 1¯, 17.23 MeV states of 12 C. To check this prediction preliminary Modified Diffraction Model (MDM) analysis of existing (3 He,t) and (3 He, 3 He') experimental data was done.