Associated Production ofΛKat theΣKThreshold

Abstract

The reaction ${\pi }^{-}+p\to \Lambda +K$ has been studied in the liquid-hydrogen bubble chamber at the threshold energy for the reaction ${\pi }^{-}+p\to \Sigma +K$. The differential cross section for $\Lambda$ production has been found to be $\frac{d\sigma }{d\Omega }=50-10\mathrm{} cos\theta -25\mathrm{} {cos}^2\theta -51\mathrm{} {cos}^3\theta +56\mathrm{} {cos}^4\theta$ μb/sr with a total cross section of 0.67±0.04 mb. The $\Lambda$'s produced are nearly completely polarized normal to the production plane, and their decay is characterized by $\left|\alpha \overline{P}\right|=0.60\mathrm{}\pm 0.05$. Two leptonic $\Lambda$ decays have been identified giving a rate for the leptonic decay consistent with one in a thousand. An unsuccessful attempt has been made to detect cusp-like effects. This attempt has failed because of the presence of high angular momentum states in the $\Lambda K$ production process.