Journal Article

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

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

2020

Overview

Abstract 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 $W_0 = -40$ 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.

• Publisher: Oxford University Press
• Subject: Collaboration / Energy / Nuclear physics / Spectrum analysis