Strange-Particle Production in π−p Interactions from 1.5 to 4.2 BeVc . II. Two-Body Final States

The reactions ${\ensuremath{\pi}}^{\ensuremath{-}}p\ensuremath{\rightarrow}\ensuremath{\Lambda}{K}^{0},{\ensuremath{\Sigma}}^{0}{K}^{0}$, and ${\ensuremath{\Sigma}}^{\ensuremath{-}}{K}^{+}$ 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 $E_{\mathrm{c}.\mathrm{m}.}^{}{}_{}{}^{\ensuremath{-}3.6}$, $E_{\mathrm{c}.\mathrm{m}.}^{}{}_{}{}^{\ensuremath{-}3.3}$, and $E_{\mathrm{c}.\mathrm{m}.}^{}{}_{}{}^{\ensuremath{-}9.3}$, respectively. The differential cross sections are presented at 11 beam momenta. A peripheral peak is the dominant feature of the reactions ${\ensuremath{\pi}}^{\ensuremath{-}}p\ensuremath{\rightarrow}\ensuremath{\Lambda}{K}^{0}$ and ${\ensuremath{\Sigma}}^{0}{K}^{0}$, for which ${K}^{*}$ exchange is allowed, but no such peaking is seen in ${\ensuremath{\pi}}^{\ensuremath{-}}p\ensuremath{\rightarrow}{\ensuremath{\Sigma}}^{\ensuremath{-}}{K}^{+}$. An exponential fit to the momentum-transfer distributions in the peripheral region yields slope parameters in the 6- to $10\ensuremath{-}{(\frac{\mathrm{BeV}}{c})}^{\ensuremath{-}2}$ range. The differential cross sections for ${\ensuremath{\pi}}^{\ensuremath{-}}p\ensuremath{\rightarrow}\ensuremath{\Lambda}{K}^{0} \mathrm{and} {\ensuremath{\Sigma}}^{\ensuremath{-}}{K}^{+}$ 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 $\ensuremath{\Lambda}$ polarization in ${\ensuremath{\pi}}^{\ensuremath{-}}p\ensuremath{\rightarrow}\ensuremath{\Lambda}{K}^{0}$ is presented.