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arXiv · 1411.6708

Observation of the "$K^-pp$"-like structure in the $d(\pi^+, K^+)$ reaction at 1.69 GeV/$c$

Abstract

We have observed a "$K^-pp$"-like structure in the $d(\pi^+,K^+)$ reaction at 1.69 GeV/$c$. In this reaction $\Lambda(1405)$ hyperon resonance is expected to be produced as a doorway to form the $K^-pp$ through the $\Lambda^*p\rightarrow K^-pp$ process. However, most of the produced $\Lambda(1405)$'s would escape from deuteron without secondary reactions. Therefore, coincidence of high-momentum ($>$ 250~MeV/$c$) proton(s) in large emission angles ($39^\circ<\theta_{lab.}<122^\circ$) was requested to enhance the signal-to-background ratio. A broad enhancement in the proton coincidence spectra are observed around the missing-mass of 2.27 GeV/$c^2$, which corresponds to the $K^-pp$ binding energy of 95 $^{+18}_{-17}$ (stat.) $^{+30}_{-21}$ (syst.) MeV and the width of 162 $^{+87}_{-45}$ (stat.) $^{+66}_{-78}$ (syst.) MeV.

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Yudai Ichikawa, Tomofumi Nagae, Hiroyuki Fujioka, Hyoungchan Bhang, Stefania Bufalino, Hiroyuki Ekawa, Petr Evtoukhovitch, Alessandro Feliciello, Shoichi Hasegawa, Shuhei Hayakawa, Ryotaro Honda, Kenji Hosomi, Kenichi Imai, Shigeru Ishimoto, Changwoo Joo, Shunsuke Kanatsuki, Ryuta Kiuchi, Takeshi Koike, Harphool Kumawat, Yuki Matsumoto, Koji Miwa, Manabu Moritsu, Megumi Naruki, Masayuki Niiyama, Yuki Nozawa, Ryosuke Ota, Atsushi Sakaguchi, Hiroyuki Sako, Valentin Samoilov, Susumu Sato, Kotaro Shirotori, Hitoshi Sugimura, Shoji Suzuki, Toshiyuki Takahashi, Tomonori Takahashi, Hirokazu Tamura, Toshiyuki Tanaka, Kiyoshi Tanida, Atsushi Tokiyasu, Zviadi Tsamalaidze, Bidyut Roy, Mifuyu Ukai, Takeshi Yamamoto, Seongbae Yang. 2014-11-25. Observation of the "$K^-pp$"-like structure in the $d(\pi^+, K^+)$ reaction at 1.69 GeV/$c$. https://doi.org/10.1093/ptep/ptv002

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