Search for KL →π0ν ν and KL →π0X0 Decays at the J-PARC KOTO Experiment

J. K. Ahn, B. Beckford, J. Beechert, K. Bryant, M. Campbell, S. H. Chen, J. Comfort, K. Dona, N. Hara, H. Haraguchi, Y. B. Hsiung, M. Hutcheson, T. Inagaki, I. Kamiji, N. Kawasaki, E. J. Kim, J. L. Kim, Y. J. Kim, J. W. Ko, T. K. KomatsubaraK. Kotera, A. S. Kurilin, J. W. Lee, G. Y. Lim, C. Lin, Q. Lin, Y. Luo, J. Ma, Y. Maeda, T. Mari, T. Masuda, T. Matsumura, D. McFarland, N. McNeal, J. Micallef, K. Miyazaki, R. Murayama, D. Naito, K. Nakagiri, H. Nanjo, H. Nishimiya, T. Nomura, M. Ohsugi, H. Okuno, M. Sasaki, N. Sasao, K. Sato, T. Sato, Y. Sato, H. Schamis, S. Seki, N. Shimizu, T. Shimogawa, T. Shinkawa, S. Shinohara, K. Shiomi, S. Su, Y. Sugiyama, S. Suzuki, Y. Tajima, M. Taylor, M. Tecchio, M. Togawa, Y. C. Tung, Y. W. Wah, H. Watanabe, J. K. Woo, T. Yamanaka, H. Y. Yoshida

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136 Citations (Scopus)


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.

Original languageEnglish
Article number021802
JournalPhysical review letters
Issue number2
Publication statusPublished - 2019 Jan 15

Bibliographical note

Publisher Copyright:
© 2019 authors. Published by the American Physical Society.

ASJC Scopus subject areas

  • Physics and Astronomy(all)


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