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

Abstract

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