Measurement of the Reactions $K^{-}p\to {\Sigma }^{+}{\pi }^{-}$ and ${\pi }^{-}p\to p{\pi }^{-}$ near the Backward Direction at 3.0 and 5.1 GeV/c

We have measured differential cross sections for $K^{-}p\to {\Sigma }^{+}{\pi }^{-}$ and ${\pi }^{-}p\to p{\pi }^{-}$ at 3.0 and 5.1 GeV/c near the backward direction. At 3.0 GeV/c both have a dip near $-u\sim 0.1$ (GeV/${\mathit{c})}^2$. At 5.1 GeV/c, $\frac{d\sigma }{\mathrm{du}}$ for ${\pi }^{-}p\to p{\pi }^{-}$ falls exponentially with slope 3.8±0.1 ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^{-2\mathrm{}}$ whereas $\frac{\mathrm{du}}{d\sigma }$ for $K^{-}p\to {\Sigma }^{+}{\pi }^{-}$ exhibits a decreasing slope for larger $\mathrm{}\left|u\right|\mathrm{}$. These data are discussed in terms of SU(3), and the relative importance of the helicity-flip and -non-flip amplitudes is investigated.