Strange-Particle Production inπ−pInteractions from 1.5 to 4.2BeVc. II. Two-Body Final States

The reactions ${\pi }^{-}p\to \Lambda K^0,{\Sigma }^0{K}^0$, and ${\Sigma }^{-}{K}^{+}$ in the 1.5- to 4.2-$\frac{\mathrm{BeV}}{c}$ momentum range were studied in the Lawrence Radiation Laboratory's 72-in. hydrogen bubble chamber. The total cross sections for the three reactions decrease as $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}^{}{}_{}{}^{-3.6\mathrm{}}$, $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}^{}{}_{}{}^{-3.3\mathrm{}}$, and $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}^{}{}_{}{}^{-9.3\mathrm{}}$, respectively. The differential cross sections are presented at 11 beam momenta. A peripheral peak is the dominant feature of the reactions ${\pi }^{-}p\to \Lambda K^0$ and ${\Sigma }^0{K}^0$, for which $K^{*}$ exchange is allowed, but no such peaking is seen in ${\pi }^{-}p\to {\Sigma }^{-}{K}^{+}$. An exponential fit to the momentum-transfer distributions in the peripheral region yields slope parameters in the 6- to $10-{\left(\frac{\mathrm{BeV}}{c}\right)}^{-2\mathrm{}}$ range. The differential cross sections for ${\pi }^{-}p\to \Lambda K^0 \mathrm{and} {\Sigma }^{-}{K}^{+}$ show peaking for forward production of hyperons in the c.m. system, to which baryon exchange is expected to contribute. The angular distribution of the $\Lambda$ polarization in ${\pi }^{-}p\to \Lambda K^0$ is presented.