The energy dependence of the (p,${\pi }^{\mathrm{-}}$) and (p,${\pi }^{+}$) reactions on ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ leading to isobaric analog states of ${}_{}{}^{14}{}_{}{}^{}\mathrm{O}$ and ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$ has been measured at a fixed four-momentum transfer at proton lab energies of 250, 354, and 489 MeV. Unlike the (p,${\pi }^{+}$) reactions, which show an enhancement of the differential cross section near the invariant mass of the ${\Delta }_{1232}$ similar to that observed for the pp→d${\pi }^{+}$ reaction at an equivalent center of mass energy and momentum transfer, the differential cross section of the (p,${\pi }^{\mathrm{-}}$) reactions decrease with increasing energy through this region. This difference is consistent with an interpretation of the (p,${\pi }^{\mathrm{-}}$) reaction mechanism as a NN→NN${\pi }^{\mathrm{-}}$ process in which nonresonant amplitudes are dominant in this region.

• Received 1 July 1987

DOI:https://doi.org/10.1103/PhysRevC.37.1161