Search for Structure inπ−p→ΛK0atΣKThreshold

We have measured the cross section, the angular distribution, and the $\Lambda$ polarization for the reaction ${\pi }^{-}p\to \Lambda K^0$. A spark-chamber spectrometer was used to collect 8400 $\Lambda K^0$ events at fourteen beam momenta near $\Sigma K$ threshold. Our data do not show the prominent cross-section enhancement suggested by some previous experiments. However, detailed structure in the cross section and the angular distribution agrees well with a simple model which includes a cusp effect at $\Sigma K$ threshold.