Hard Scattering with Exclusive Reactions:π−pElastic Scattering andρ-Meson Production

Initial results are presented from an experiment designed to test the dynamics of large-angle exclusive scattering. Cross sections are given for two reactions near 90° c.m., ${\pi }^{-}p\to {\pi }^{-}p\left(\mathrm{elastic}\right)$ and ${\pi }^{-}p\to {\rho }^{-}p$, where $t=-8.9\mathrm{}$ Ge${\mathrm{V}}^2$/${\mathit{c}}^2$ for 9.9-GeV/c incident pions. The ratio of $\frac{{\rho }^{-}p}{\mathrm{elastic}}$ is large, $\frac{2}{3}$, and remarkably similar to measurements for small-angle scattering.