$\Lambda d$ correlations from the $^4$He(stopped-$K^-$,$d$) reaction

Abstract

We have observed an intense high-energy component in an inclusive $^4$He(stopped $K^-$, $d$) spectrum. For back-to-back $\Lambda d$ pairs a prominent event cluster has been found just below the $m_{^4\textrm{He}}+m_{K^-}-m_{n}$ mass threshold in the $\Lambda d$ invariant mass spectrum of $\Lambda dn$ events, which is evidence for a three-nucleon absorption process of $K^-$ in $^4$He. In addition, an appreciable strength is revealed below $\sim$3220 MeV/$c^2$. Well separated $\Sigma^0 dn$ events show a peak similar to the case of $\Lambda dn$.