Angular distributions of the analyzing power $A\left(\theta \right)$ and the differential cross section $\frac{d\sigma \left(\theta \right)}{d\Omega }$ for the reaction ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$($p_{\mathrm{pol}}$, ${\pi }^{-}$)${}_{}{}^{10}{}_{}{}^{}\mathrm{C}$(g.s.) have been measured with 200-MeV polarized protons at laboratory angles between 25° and 150°. The measured $A\left(\theta \right)$, which is negative for ${{\theta }_{\pi }}^{\mathrm{c}.\mathrm{m}.\mathrm{}}\lesssim 70°$ and positive thereafter, is quite different from those of ($p_{\mathrm{pol}}$,${\pi }^{+}$) reactions, for which $A\left(\theta \right)$ is typically negative at all angles. The present $\frac{d\sigma \left(\theta \right)}{d\Omega }$ is backward peaked, unlike all previously measured ($p$,${\pi }^{-}$) distributions.

• Received 11 July 1980

DOI:https://doi.org/10.1103/PhysRevLett.45.1769