Backward Peaks in Elastic Pion-Proton Scattering from 6 to 17 GeV/c

The energy dependence, charge dependence, and angular distributions of pion-proton elastic scattering near 180° have been measured at beam momenta from 5.9 to 17.1 GeV/c. The 180° cross sections decrease with energy as ${P_{\mathrm{lab}}}^{-1.1\mathrm{}}$ for ${\pi }^{-}-p$ and ${P_{\mathrm{lab}}}^{-1.4\mathrm{}}$ for ${\pi }^{+}-p$. At all energies the ${\pi }^{+}-p$ backward peak is quite sharp and has a width about ½ that of the forward diffraction peak. The ${\pi }^{-}-p$ backward peaks are about twice as wide as the forward diffraction peak and appear to go through a maximum before reaching 180°.