The total cross section and angular distributions for the differential cross section and the analyzing power of the exclusive two-body pion production reaction ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(p→,${\mathrm{\pi }}^0$) ${}_{}{}^{13}{}_{}{}^{}\mathrm{N}_{\mathrm{g}.\mathrm{s}.\mathrm{}}^{}{}_{}{}^{}$ have been measured at 147 MeV, very near the threshold energy of 145 MeV. Both the large forward-backward asymmetry in the angular distribution of the differential cross section and the large values observed for the analyzing powers indicate strong interference between the amplitude for s-wave pion emission and the amplitudes for p-wave pion emission. A phase-shift analysis performed on these new data yields significant p-wave strength at this low energy. The measurements for ${\mathrm{\pi }}^0$ production from carbon are in agreement with results extracted from existing data for ${\mathrm{\pi }}^{+}$ production from carbon, after corrections for isospin invariance and Coulomb effects. The reduced s-wave strength is found to have a simple power law dependence on the total number of nucleons in the final bound state.

• Received 2 August 1993

DOI:https://doi.org/10.1103/PhysRevC.48.2763