Structure of S=−2 Hypernuclei and Hyperon–Hyperon Interactions

Abstract

We review recent progress in S=−2 hypernuclei such as double-Λ hypernuclei and Ξ hypernuclei, which are composed of a nucleus and one or two hyperons, such as a Λ or a Ξ particle. Through observations of [Formula: see text]He, such as the Nagara event, we obtain important information about the ΛΛ interaction. Using this information, we perform a four-body calculation of ααΛΛ for [Formula: see text]Be, which was observed at KEK as the Demachi–Yanagi event. We interpret this event as the [Formula: see text] excited state. We calculate energy levels of [Formula: see text]Be within the framework of an αα nΛΛ five-body cluster model, and then interpret the Hida event, which was observed at KEK as the ground state of [Formula: see text]Be. Motivated by observation of the Kiso event of [Formula: see text]C, by using the Skyrme–Hartree–Fock and relativistic mean-field frameworks, we calculate the energy spectra of this hypernucleus. We interpret this event as the 14N(g.s.)+Ξ−(0 p) state. Finally, we propose an experiment on [Formula: see text]H and [Formula: see text]Li to extract information about the spin- and isospin-averaged parts of the Ξ N interaction.