An event excess observed in the deeply bound region of the 12C (K-, p) missing-mass spectrum

Yudai Ichikawa, Junko Yamagata-Sekihara, Jung Keun Ahn, Yuya Akazawa, Kanae Aoki, Elena Botta, Hiroyuki Ekawa, Petr Evtoukhovitch, Alessandro Feliciello, Manami Fujita, Toshiyuki Gogami, Shoichi Hasegawa, Tomoyuki Hasegawa, Shuhei Hayakawa, Tomonori Hayakawa, Satoru Hirenzaki, Ryotaro Honda, Kenji Hosomi, Ken'Ichi Imai, Wooseung JungShunsuke Kanatsuki, Shin Hyung Kim, Shinji Kinbara, Kazuya Kobayashi, Jaeyong Lee, Simonetta Marcello, Koji Miwa, Taejin Moon, Tomofumi Nagae, Yoshiyuki Nakada, Manami Nakagawa, Takuya Nanamura, Megumi Naruki, Atsushi Sakaguchi, Hiroyuki Sako, Susumu Sato, Yuki Sasaki, Kotaro Shirotori, Hitoshi Sugimura, Toshiyuki Takahashi, Hirokazu Tamura, Kiyoshi Tanida, Zviadi Tsamalaidze, Mifuyu Ukai, Takeshi O. Yamamoto

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4 Citations (Scopus)


We have measured, for the first time, the inclusive missing-mass spectrum of the {12}C(K-, p) reaction at an incident kaon momentum of 1.8 GeV/c at the J-PARC K1.8 beamline. We observed a prominent quasi-elastic peak (K-p \rightarrow K-p) in this spectrum. In the quasi-elastic peak region, the effect of secondary interaction is apparently observed as a peak shift, and the peak exhibits a tail in the bound region. We compared the spectrum with a theoretical calculation based on the Green's function method by assuming different values of the parameters for the \bar{K}-nucleus optical potential. We found that the spectrum shape in the binding-energy region -300 \, \text{MeV} < B{K} < 40 MeV is best reproduced with the potential depths V_0 = -80 MeV (real part) and W0 = -40 MeV (imaginary part). On the other hand, we observed a significant event excess in the deeply bound region around B{K} \sim 100 MeV, where the major decay channel of K- NN \to \pi\Sigma N is energetically closed, and the non-mesonic decay modes (K- NN \to \Lambda N and \Sigma N) should mainly contribute. The enhancement is fitted well by a Breit-Wigner function with a kaon-binding energy of 90 MeV and width 100 MeV. A possible interpretation is a deeply bound state of a Y{∗}-nucleus system.

Original languageEnglish
Article number123D01
JournalProgress of Theoretical and Experimental Physics
Issue number12
Publication statusPublished - 2020 Dec 1


  • D33

ASJC Scopus subject areas

  • Physics and Astronomy(all)


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