Pion single charge exchange onC14

Forward-angle differential cross sections for the isobaric-analog state in the ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}({\pi }^{+}, {\pi }^0){}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ reaction were measured at 100, 165, 230, and 295 MeV. The extracted excitation function is found to have a maximum near 200 MeV and its shape resembles that of the free $\pi \mathrm{N}$ cross sections. Impulse-approximation calculations with optical potentials linear in the nuclear density do not reproduce the trends of the data. Systematics of 0° cross sections with $N$ and $Z$ are presented.