We have performed an exclusive measurement of the $K^{-}+\! ~^{3}{\rm He} \to \Lambda pn$ reaction at an incident kaon momentum of $1 {\rm GeV}/c$. In the $\Lambda p$ invariant mass spectrum, a clear peak was observed below the mass threshold of $\bar{K}+N+N$, as a signal of the kaonic nuclear bound state, $\KNN$. The binding energy, decay width, and $S$-wave Gaussian reaction form-factor of this state were observed to be $B_{K} = \valB$, $\Gamma_{K} = \valG$, and $Q_{K} = \valQ$, respectively. The total production cross-section of $\KNN$, determined by its $\Lambda p$ decay mode, was $\sigma^{tot}_{K} \cdot \BR_{\Lambda p} = \valCSLp$. We estimated the branching ratio of the $\KNN$ state to the $\Lambda p$ and ${\Sigma }^{0}p$ decay modes as $\BR_{\Lambda p}/\BR_{\Sigma^{0}p} \sim \valBR$, by assuming that the physical processes leading to the $\SNN$ final states are analogous to those of $\Lambda pn$.

中文翻译：

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在$ {^ {3} {\ rm He}（K ^ {-}，\ Lambda p）n} $反应中观察到aK¯NNbound状态

我们已经对$ K ^ {-} + \进行了独家测量！〜^ {3} {\ rm He} \以\ $ 1 {\ rm GeV} / c $的事件kaon动量对\ Lambda pn $反应。在里面$\Lambda p$ 不变的质谱图，在低于的质量阈值时观察到一个清晰的峰 $\stackrel{〜}{ķ}+ñ+ñ$，作为钾离子核束缚态的信号$ \ KNN $。结合能，衰变宽度和$\mathrm{小号}$该状态的波高斯反应形式因子分别为$ B_ {K} = \ valB $，$ \ Gamma_ {K} = \ valG $和$ Q_ {K} = \ valQ $。$ \ KNN $的总生产横截面，由$\Lambda p$衰减模式为$ \ sigma ^ {tot} _ {K} \ cdot \ BR _ {\ Lambda p} = \ valCSLp $。我们估算了$ \ KNN $状态与$\Lambda p$ 和 ${\Sigma }^{0}p$假定导致$ \ SNN $最终状态的物理过程与以下过程类似，则衰减模式为$ \ BR _ {\ Lambda p} / \ BR _ {\ Sigma ^ {0} p} \ sim \ valBR $：$\Lambda pñ$。