Energy dependence of the /sup 12/C(p,π+)/sup 13/C reaction in the region of the Δ/sub 1232/ resonance

Differential cross sections for the /sup 12/C(p,π+) /sup 13/C/sup */ reaction at T/sub p/ = 250, 354, and 489 MeV are presented and compared with previously published data taken at other energies in the Δ/sub 1232/ resonance region. At fixed four momentum transfers greater than 0.4 GeV2/c2, the differential cross sections exhibit a maximum near the invariant mass of the Δ/sub 1232/. This energy dependence is similar to that shown by the pp→dπ+ reaction at equivalent energy, and provides strong evidence of a NN→NNπ+ process in the (p,π+) reaction mechanism. The total cross section for each transition exhibits a maximum at an energy about 100 MeV lower than that expected from the Δ/sub 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 Δ/sub 1232/ in the (p,π+) reaction mechanism, and the decrease in cross section due to the large momentum transfers that the reaction is restricted to at higher energies