Spin-isospin excitation in 12C(γ,π+)12B* using tagged photons

The energy spectra of positive pions from the reaction 12C(γ,π+)12B* were measured at five angles, using quasi-monochromatic, tagged photons in the energy range from 176 to 182 MeV. Strong transitions to the isovector nuclear states in 12B at 0-1, 4.5, and 7.5 MeV were observed. The differential cross sections to these states have been obtained for the momentum transfers 0.5<q<1.2 fm-1. DWIA calculations have been carried out in momentum space for each observed state or group of states. Comparisons are made between the present data, previous data from bremsstrahlung experiments, and various DWIA calculations. (orig.)