Progress on the study of double-Λ hypernuclei

With use of nuclear emulsion, double-hypernuclei have been studied for aiming to understand Λ-Λ interaction via at-rest-capture of Ξ^- hyperon originated by quasi-free (K^-, K⁺) reactions, where the beam K^- momentum was 1.66 GeV/c. Under the process for studying them, elementary feature for not only quasi-free reaction but also production of nuclei with single and double unit(s) of strangeness have been roughly understood, even the statistics were not large. So far we have succeeded to analyze 5 events of double-hypernuclei which introduced binding energies of two A hyperons on several nuclei. However its knowledge is very limited. We have started a new experiment, J-PARC E07, to give us rich information in S -2 world. An event which may give us a new information about Ξ-nucleus interaction shall be introduced.