Interpretation of a double hypernucleus event

Arguments are put forward to suggest that a double hypernucleus event, recently reported by Aoki et al. as either ${}_{\Lambda \Lambda }{}^{10}{}_{}{}^{}\mathrm{Be}$ or ${}_{\Lambda \Lambda }{}^{13}{}_{}{}^{}\mathrm{B}$, should be interpreted as ${}_{\Lambda \Lambda }{}^{13}{}_{}{}^{}\mathrm{B}$. It is proposed that the formation of ${}_{\Lambda \Lambda }{}^{13}{}_{}{}^{}\mathrm{B}$ occurs sequentially via an intermediate excited state of ${}_{\Lambda \Lambda }{}^{14}{}_{}{}^{}\mathrm{C}$, which decays by proton emission: ${\Xi }^{-}+{}_{}{}^{14}{}_{}{}^{}\mathrm{N}\to n+{}_{\Lambda \Lambda }{}^{14}{}_{}{}^{}\mathrm{C}_{}^{*}{}_{}{}^{}$, ${}_{\Lambda \Lambda }{}^{14}{}_{}{}^{}\mathrm{C}_{}^{*}{}_{}{}^{}\to p+{}_{\Lambda \Lambda }{}^{13}{}_{}{}^{}\mathrm{B}$. Moreover, it is shown that particular excited states are favored in the ${\Xi }^{-}$ hyperon capture process. The binding energy of the two $\Lambda$ hyperons in ${}_{\Lambda \Lambda }{}^{13}{}_{}{}^{}\mathrm{B}$ is $B_{\Lambda \Lambda }=27.5\mathrm{}\pm 0.7$ MeV, corresponding to an attractive $s_{\Lambda }^2$ matrix element $\Delta B_{\Lambda \Lambda }=4.8\mathrm{}\pm 0.7$ MeV, in good agreement with values of $\Delta B_{\Lambda \Lambda }$ obtained from previous events.