First observation of a nuclear -state of a hypernucleus,

Yoshimoto, Masahiro*; Fujita, Manami; Hashimoto, Tadashi   ; Hayakawa, Shuhei; Ichikawa, Yudai   ; Ichikawa, Masaya; Imai, Kenichi*; Nanamura, Takuya; Naruki, Megumi; Sako, Hiroyuki   ; Sato, Susumu  ; Tamura, Hirokazu; Tanida, Kiyoshi   ; Yamamoto, Takeshi  ; 35 of others*

Bound-systems of - are studied via capture at rest followed by emission of a twin single- hypernucleus in the emulsion detectors. Two events forming extremely deep bound states were obtained by analysis of a hybrid method in the E07 experiment at J-PARC and reanalysis of the E373 experiment at KEK-PS. The decay mode of one event was assigned as +++. Since there are no excited states for daughter particles, the binding energy of the hyperon, , in nucleus was uniquely determined to be 6.27 0.27 MeV. Another - system via the decay + + brings a value, 8.00 0.77 MeV or 4.96 0.77 MeV, where the two possible values of correspond to the ground and the excited states of the daughter nucleus, respectively. Because the values are larger than those of the previously reported events (KISO and IBUKI), which are both interpreted as the nuclear state of the - system, these new events give the first indication of the nuclear state of the hypernucleus, .