The interaction energy between Λ hyperons and the presence or absence of Ξ hypernuclei (is Ξ hyperons bound to the nuclei?), which can be obtained from doubly-strange hypernuclei, are essential information for a unified understanding of baryons under SU(3)f symmetry. Especially in recent years, they are also valuable information for understanding the existence of neutron stars. Over the past 40 years, doubly-strange hypernucleus search experiments have been conducted in Japan using nuclear emulsion, and 47 samples of doubly-strange hypernuclei have been detected. From the double-Λ hypernuclei, we know that the Λ-Λ interaction between two Λ hyperons is weakly attractive and that the binding energy of two Λ hyperons by the nucleus seems to depend linearly on the nuclear mass number. In addition, the Ξ hypernucleus does indeed exist, the attraction between Ξ hyperon and nucleon works, and the level structure of the 15ΞC hypernucleus can now be inferred. Efforts are being made to further explore the entire emulsion volume to dramatically improve the number of the samples of doubly-strange hypernuclei.
|Collaboration||KEK-E176, E373, J-PARC E07, and Emulsion-ML|