Differential cross sections for the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(p,${\pi }^{+}$${)\mathrm{}}^{13}$${\mathrm{C}}^{\mathrm{*}}$ reaction at $T_{\mathrm{p}=250\mathrm{}}$, 354, and 489 MeV are presented and compared with previously published data taken at other energies in the ${\Delta }_{1232}$ resonance region. At fixed four momentum transfers greater than 0.4 ${\mathrm{GeV}}^2$/$c^2$, the differential cross sections exhibit a maximum near the invariant mass of the ${\Delta }_{1232}$. This energy dependence is similar to that shown by the pp→d${\pi }^{+}$ reaction at equivalent energy, and provides strong evidence of a NN→NN${\pi }^{+}$ process in the (p,${\pi }^{+}$) reaction mechanism. The total cross section for each transition exhibits a maximum at an energy about 100 MeV lower than that expected from the ${\Delta }_{1232}$ invariant mass. This energy dependence could be the result of an interplay between the increase in cross section due to the role of the ${\Delta }_{1232}$ in the (p,${\pi }^{+}$) reaction mechanism, and the decrease in cross section due to the large momentum transfers that the reaction is restricted to at higher energies.

• Received 23 March 1987

DOI:https://doi.org/10.1103/PhysRevC.36.1058