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Ahn, J. K.; Beckford, B.; Beechert, J.; Bryant, K.; Campbell, M.; Chen, S. H.; Comfort, J.; Dona, K.; Hara, N.; Haraguchi, H.; Hsiung, Y. B.; Hutcheson, M.; Inagaki, T.; Kamiji, I.; Kawasaki, N.; Kim, E. J.; Kim, J. L.; Kim, Y. J.; Ko, J. W.; Komatsubara, T. K.; Kotera, K.; Kurilin, A. S.; Lee, J. W.; Lim, G. Y.; Lin, C.; Lin, Q.; Luo, Y.; Ma, J.; Maeda, Y.; Mari, T.; Masuda, T.; Matsumura, T.; Mcfarland, D.; McNeal, N.; Micallef, J.; Miyazaki, K.; Murayama, R.; Naito, D.; Nakagiri, K.; Nanjo, H.; Nishimiya, H.; Nomura, T.; Ohsugi, M.; Okuno, H.; Sasaki, M.; Sasao, N.; Sato, K.; Sato, T.; Sato, Y.; Schamis, H.; Seki, S.; Shimizu, N.; Shimogawa, T.; Shinkawa, T.; Shinohara, S.; Shiomi, K.; Su, S.; Sugiyama, Y.; Suzuki, S.; Tajima, Y.; Taylor, M.; Tecchio, M.; Togawa, M.; Tung, Y. C.; Wah, Y. W.; Watanabe, H.; Woo, J. K.; Yamanaka, T.; Yoshida, H. Y.
Physical review letters, 01/2019, Letnik: 122, Številka: 2Journal Article
A search for the rare decay KL → π0νν¯ was performed. With the data collected in 2015, corresponding to 2.2 × 1019 protons on target, a single event sensitivity of (1.30 ± 0.01stat ± 0.14syst) × 10–9 was achieved and no candidate events were observed. We set an upper limit of 3.0 × 10–9 for the branching fraction of KL → π0νν¯ at the 90% confidence level (C.L.), which improved the previous limit by almost an order of magnitude. An upper limit for KL → π0X0 was also set as 2.4 × 10–9 at the 90% C.L., where X0 is an invisible boson with a mass of 135 MeV /c2.
