Differential cross sections and analyzing powers for the ${}_{}{}^7{}_{}{}^{}(\mathit{p}\to$,${\pi }^{\pm }$) reactions leading to discrete states of ${}_{}{}^8{}_{}{}^{}\mathrm{B}$ and ${}_{}{}^8{}_{}{}^{}\mathrm{Li}$, as well as to the continuum, are presented at $T_p$=280, 354, and 489 MeV. These results are compared with previously published results at 200 and 250 MeV. At fixed four-momentum transfers squared in the region 0.6>t>0.4 ${\mathrm{GeV}}^2$/${\mathrm{c}}^2$, the energy dependence of the (p,${\pi }^{+}$) and (p,${\pi }^{\mathrm{-}}$) differential cross sections is quite similar, in sharp contrast to earlier results from the ${}_{}{}^{13}{}_{}{}^{}(\mathit{p}$,${\pi }^{\pm }$) reactions. The observed variations in the (p,${\pi }^{\mathrm{-}}$) energy dependence are presumed to reflect differences in the relative importance of resonant and nonresonant amplitudes in the (p,${\pi }^{\mathrm{-}}$) reaction mechanism. The analyzing powers of the (p→,${\pi }^{\mathrm{-}}$) and (p→,${\pi }^{+}$) reactions are qualitatively very similar except for a difference in sign.

• Received 29 April 1988

DOI:https://doi.org/10.1103/PhysRevC.38.1304