Jπ decomposition of a bump at Ex≃7 MeV in 12N

The 12C(d,2He)12B measurement by Okamura et al. has shown that the spin-dipole resonance bump at Ex≃7.5 MeV in 12B is most probably due mainly to the 2− states. This fact disagrees with the widely accepted assignment as 1−. Motivated by this work we studied the spin-parity of the mirror state located at Ex≃7 MeV in 12N by measuring a complete set of polarization transfer (PT) coefficients for the 12C(p,n)12N reaction at 0°. We employed a 300 MeV polarized proton beam and the NTOF facility at the Research Center for Nuclear Physics. The PT coefficients enable us to disentangle the bump into spin-parity components as 1ΔS=0−: 1ΔS=1−: 2ΔS=1−=0.08±0.02: 0.17±0.04: 0.75±0.04 in a plane-wave impulse approximation neglecting the contribution of the 0− states. This result clearly indicates that the dominant component of the bump is due to the 2− states and strongly supports the conclusion of Okamura et al.