  Correlations of back-to-back coincident $\Lambda d$ and $\Lambda t$ pairs
from the stopped $K^-$ reaction on $^4$He had been investigated, thereby
$\Lambda d$ and $\Lambda t$ 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-$K^-$)$_{atomic} \rightarrow \Lambda d "n"$, is estimated to be $(0.9
\pm 0.1 (stat) \pm 0.2 (syst)) \times 10^{-3}$ from the normalized $\Lambda d$
spectrum in a $\Lambda d n$ final state, while the fraction of the four-nucleon
process, ($^4$He-$K^-$)$_{atomic} \rightarrow \Lambda t$, is obtained to be
$(3.1 \pm 0.4 (stat) \pm 0.5 (syst)) \times 10^{-4}$ per stopped $K^-$.
