Measurement of the C12(p,0)13N reaction by recoil detection

Differential cross sections for the neutral pion production reaction C12(p,0)13Ng.s. have been measured at 153.5, 166.1, 186.0, and 204.0 MeV bombarding energy using recoil detection. The shape of the angular distribution agrees well with that of the mirror reaction C12(p,)13Cg.s.. Isospin invariance predicts for the ratio of the cross sections (p,)/ (p,0)=2. At 153.5, 166.1, and 186.0, MeV, where (p,) cross sections have been reported previously by other groups at the same reduced pion momentum p/mc=0.34,0.55,0.78, the ratio of the total cross sections is 2.020.14, 3.140.12, and 2.120.16, respectively. The (p,0) cross sections at 166 MeV is therefore 1.570.06 times larger than expected. For Tp<160 MeV, the experimental cross sections are larger than predicted by a phase space and Coulomb barrier penetration calculation that fits the higher-energy data. Differential cross sections were also obtained for the C12(p,-)13O reaction, and upper limits set for differential cross sections for radiative capture to the ground state of N13.