Structure near \(K^-\)+\(p\)+\(p\) threshold in the in-flight \(^3\)He\((K^-,\Lambda p)n\) reaction

• Published in: arXiv.org 2016-03
• Main Authors: J-PARC E15 Collaboration, Sada, Y, Ajimura, S, Bazzi, M, Beer, G, Bhang, H, Bragadireanu, M, Buehler, P, Busso, L, Cargnelli, M, Choi, S, Curceanu, C, Enomoto, S, Faso, D, Fujioka, H, Fujiwara, Y, Fukuda, T, Guaraldo, C, Hashimoto, T, Hayano, R S, Hiraiwa, T, Iio, M, Iliescu, M, Inoue, K, Ishiguro, Y, Ishikawa, T, Ishimoto, S, Ishiwatari, T, Itahashi, K, Iwai, M, Iwasaki, M, Kato, Y, Kawasaki, S, Kienle, P, Kou, H, Y Ma, Marton, J, Matsuda, Y, Mizoi, Y, Morra, O, Nagae, T, Noumi, H, Ohnishi, H, Okada, S, Outa, H, Piscicchia, K, A Romero Vidal, Sakaguchi, A, Sakuma, F, Sato, M, Scordo, A, Sekimoto, M, Shi, H, Sirghi, D, Sirghi, F, Suzuki, K, Suzuki, S, Suzuki, T, Tanida, K, Tatsuno, H, Tokuda, M, Tomono, D, Toyoda, A, Tsukada, K, O Vazquez Doce, Widmann, E, Wuenschek, B K, Yamaga, T, Yamazaki, T, Yim, H, Zhang, Q, Zmeskal, J
• Format: Article
• Language: English
• Subjects: Form factors; Kinetic energy; Missing mass (astrophysics); Momentum transfer
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1601.06876

To search for an S= -1 di-baryonic state which decays to \(\Lambda p\), the \( {\rm{}^3He}(K^-,\Lambda p)n_{missing}\) reaction was studied at 1.0 GeV/\(c\). Unobserved neutrons were kinematically identified from the missing mass \(M_X\) of the \( {\rm{}^3He}(K^-,\Lambda p)X\) reaction in order to have a large acceptance for the \(\Lambda pn\) final state. The observed \(\Lambda p n\) events, distributed widely over the kinematically allowed region of the Dalitz plot, establish that the major component comes from a three nucleon absorption process. A concentration of events at a specific neutron kinetic energy was observed in a region of low momentum transfer to the \(\Lambda p\). To account for the observed peak structure, the simplest S-wave pole was assumed to exist in the reaction channel, having Breit-Wigner form in energy and with a Gaussian form-factor. A minimum \(\chi^2\) method was applied to deduce its mass \(M_X\ =\) 2355 \( ^{+ 6}_{ - 8}\) (stat.) \( \pm 12\) (syst.) MeV/c\(^2\), and decay-width \(\Gamma_X\ = \) 110 \( ^{+ 19}_{ - 17}\) (stat.) \( \pm 27\) (syst.) MeV/c\(^2\), respectively. The form factor parameter \(Q_X \sim\) 400 MeV/\(c\) implies that the range of interaction is about 0.5