Five-body cluster structure of double-$\mathrm{\Lambda }$ hypernucleus ${}_{\mathrm{\Lambda }\mathrm{\Lambda }}^{11}$Be

Energy levels of the double $\mathrm{\Lambda }$ hypernucleus, $^{11}{\Lambda \Lambda}$Bearecalculatedwithintheframeworkofan$\alpha \alpha n \Lambda \Lambda$ five-body model. Interactions between constituent particles are determined so as to reproduce reasonably the observed low-energy properties of the $\alpha \alpha$, $\alpha \alpha n$ nuclei and the existing data for $\mathrm{\Lambda }$-binding energies of the $\alpha \mathrm{\Lambda }$, $\alpha \alpha \mathrm{\Lambda }$, $\alpha n\mathrm{\Lambda }$ and $\alpha \alpha n\mathrm{\Lambda }$ systems. An effective $\Lambda \Lambda$interactionisconstructedsoastoreproduce,withinthe$\alpha \Lambda \Lambda$three-bodymodel,the$B{\Lambda \Lambda}$of$^6_{\Lambda \Lambda}$He, which was extracted from the emulsion experiment, the NAGARA event. With no adjustable parameters for the $\alpha \alpha n\mathrm{\Lambda }\mathrm{\Lambda }$ system, $B_{\mathrm{\Lambda }\mathrm{\Lambda }}$ of the ground and bound excited states of ${}_{\mathrm{\Lambda }\mathrm{\Lambda }}^{11}$Be are calculated with the Gaussian Expansion Method. The Hida event, recently observed at KEK-E373 experiment, is interpreted as an observation of the ground state of the ${}_{\mathrm{\Lambda }\mathrm{\Lambda }}^{11}$Be.