XVIII International Conference on Hadron Spectroscopy and Structure (HADRON2019)

Double Λ hypernuclei and Ξ hypernuclei, collectively called “double hypernuclei”, have come to play important roles in hadron nuclear physics as valuable information sources of baryon-baryon interaction. The most effective method to investigate them is event-by-event analysis with photographic emulsion sheets. An emulsion experiment to detect double hypernuclei has been performed in the J-PARC hadron facility in 2016-17. By this experiment, quantitative data on ΛΛ or Ξ*N* interaction in a nucleus are being accumulated successfully. A new nuclide of double hypernucleus, _ΛΛBe, was observed in this experiment. This event was interpreted as the production and decay of ¹⁰ _ΛΛBe, ¹¹ _ΛΛBe, or ¹² _ΛΛBe* via Ξ ^-capture in Oxygen-16. Several other interesting events have been found and further event search is going on.