Positive-Pion Production by 160-MeV Protons onZr90andPb208

Abstract

Angular distributions for the reactions $^{98}\mathrm{Zr}(p, {\ensuremath{\pi}}^{+})^{91}\mathrm{Zr}(\mathrm{g}.\mathrm{s}.)$ and $^{208}\mathrm{Pb}(p, {\ensuremath{\pi}}^{+})^{209}\mathrm{Pb}(0.0, 0.78, \mathrm{and} 1.41 \mathrm{MeV})$ at 160 MeV have been measured from 25 to 155 deg using a quadrupole-dipole-dipole-multipole magnetic spectrograph. The $^{90}\mathrm{Zr}$ angular distribution has a shallow minimum at about 80 deg; the $^{208}\mathrm{Pb}$ angular distributions have minima at more forward angles and rise markedly in the backward hemisphere. The ($p, {\ensuremath{\pi}}^{+}$) cross sections observed in this mass region depend weakly on target mass and angular momentum transfer.