S = -2 hypernuclear structure

The structure of light hypernuclei with strangeness S= -2 is investigated with the three-, four-, and five-body cluster model and the Gaussian Expansion method (GEM). Energy levels of the double-Λ hypernuclei _ΛΛ⁷He, _ΛΛ ⁷Li, _ΛΛ⁸Li, _ΛΛ⁹Li, _ΛΛ ⁹Be, and _ΛΛ¹⁰Be are predicted with the framework of αxΛΛ four-body model, where x = n,p,d,t, ³He, and α, respectively. Also, energy levels of the double Λ hypernucleus, _ΛΛ¹¹Be are calculated within the framework of a ααnΛΛ five-body model. The Demachi-Yanagi event, identified as _ΛΛ ¹⁰Be, is interpreted as an observation of its 2⁺ state excited state. The Hida event, recently observed at KEK-E373 experiment, is interpreted as an observation of the ground state of the _ΛΛ¹¹Be. Detailed structure calculations in _Ξ¹²-Be, _Ξ⁵-H, _Ξ⁹-Li, _Ξ⁷-H and _Ξ¹⁰-Li are performed within the framework of the microscopic two-, three- and four-body cluster models. _Ξ ⁷-H and _Ξ¹⁰-Li are predicted to have bound states.