Three- and four-nucleon absorption processes observed in the $K^{-}$-${}^4$He reaction at rest

Abstract

Correlations of back-to-back coincident $\hat{I}›d$ and $\hat{I}›t$ pairs from the stopped $K^{-}$ reaction on ${}^4$He had been investigated, thereby $\hat{I}›d$ and $\hat{I}›t$ branches of non-mesonic three- and four-nucleon absorption processes of antikaon at rest were identified as well-separable processes, respectively. The branching ratio of the three-nucleon process, (${}^4$He-$K^{-}$)${}_{atomic}\to \hat{I}›d"n"$, is estimated to be $(0.9\pm 0.1(stat)\pm 0.2(syst))\times 10^{-3}$ from the normalized $\hat{I}›d$ spectrum in a $\hat{I}›dn$ final state, while the fraction of the four-nucleon process, (${}^4$He-$K^{-}$)${}_{atomic}\to \hat{I}›t$, is obtained to be $(3.1\pm 0.4(stat)\pm 0.5(syst))\times 10^{-4}$ per stopped $K^{-}$.

6 pages, 4 figures, to be submitted to Physics Letters B