Observation of a Be double-Lambda hypernucleus in the J-PARC E07 experiment

Abstract

A double-Λ hypernucleus, ΛΛ Be, was observed by the J-PARC E07 Collaboration in nuclear emulsions tagged by the (K-, K+) reaction. This event was interpreted as the production and decay of _ΛΛ;10 Be, ΛΛ;11 Be, or ΛΛ;12 Be∗ via Xi- capture in 16 O. By assuming capture in the atomic 3D state, the binding energies of two Λ hyperons (B_ΛΛ) of these double-Λ hypernuclei are obtained to be 15.05 pm 0.11,mathrmMeV, 19.07 pm 0.11,mathrmMeV, and 13.68 pm 0.11,mathrmMeV, respectively. Based on the kinematic fitting, ΛΛ;11 Be is the most likely explanation for the observed event.