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arXiv · 2506.14406

Search for neutron decay into an antineutrino and a neutral kaon in 0.401 megaton-years exposure of Super-Kamiokande

Kamiokande Collaboration·K. Yamauchi·K. Abe·S. Abe·Y. Asaoka·M. Harada·Y. Hayato·K. Hiraide·K. Hosokawa·K. Ieki·M. Ikeda·J. Kameda·Y. Kanemura·Y. Kataoka·S. Miki·S. Mine·M. Miura·S. Moriyama·M. Nakahata·S. Nakayama·Y. Noguchi·G. Pronost·K. Sato·H. Sekiya·K. Shimizu·R. Shinoda·M. Shiozawa·Y. Suzuki·A. Takeda·Y. Takemoto·H. Tanaka·T. Yano·Y. Itow·T. Kajita·R. Nishijima·K. Okumura·T. Tashiro·T. Tomiya·X. Wang·P. Fernandez·L. Labarga·D. Samudio·B. Zaldivar·B. W. Pointon·C. Yanagisawa·E. Kearns·J. Mirabito·L. Wan·T. Wester·J. Bian·B. Cortez·N. J. Griskevich·Y. Jiang·M. B. Smy·H. W. Sobel·V. Takhistov·A. Yankelevich·J. Hill·M. C. Jang·S. H. Lee·D. H. Moon·R. G. Park·B. S. Yang·B. Bodur·K. Scholberg·C. W. Walter·A. Beauchêne·O. Drapier·A. Ershova·Th. A. Mueller·A. D. Santos·P. Paganini·C. Quach·R. Rogly·T. Nakamura·J. S. Jang·R. P. Litchfield·L. N. Machado·F. J. P. Soler·J. G. Learned·K. Choi·N. Iovine·D. Tiwari·S. Cao·L. H. V. Anthony·D. Martin·N. W. Prouse·M. Scott·Y. Uchida·V. Berardi·N. F. Calabria·M. G. Catanesi·N. Ospina·E. Radicioni·A. Langella·G. De Rosa·G. Collazuol·M. Feltre·M. Mattiazzi·L. Ludovici
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Abstract

We searched for bound neutron decay via $n\to\bar{\nu}+K^0$ predicted by the Grand Unified Theories in 0.401 Mton$\cdot$years exposure of all pure water phases in the Super-Kamiokande detector. About 4.4 times more data than in the previous search have been analyzed by a new method including a spectrum fit to kaon invariant mass distributions. No significant data excess has been observed in the signal regions. As a result of this analysis, we set a lower limit of $7.8\times10^{32}$ years on the neutron lifetime at a 90% confidence level.

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Kamiokande Collaboration, K. Yamauchi, K. Abe, S. Abe, Y. Asaoka, M. Harada, Y. Hayato, K. Hiraide, K. Hosokawa, K. Ieki, M. Ikeda, J. Kameda, Y. Kanemura, Y. Kataoka, S. Miki, S. Mine, M. Miura, S. Moriyama, M. Nakahata, S. Nakayama, Y. Noguchi, G. Pronost, K. Sato, H. Sekiya, K. Shimizu, R. Shinoda, M. Shiozawa, Y. Suzuki, A. Takeda, Y. Takemoto, H. Tanaka, T. Yano, Y. Itow, T. Kajita, R. Nishijima, K. Okumura, T. Tashiro, T. Tomiya, X. Wang, P. Fernandez, L. Labarga, D. Samudio, B. Zaldivar, B. W. Pointon, C. Yanagisawa, E. Kearns, J. Mirabito, L. Wan, T. Wester, J. Bian, B. Cortez, N. J. Griskevich, Y. Jiang, M. B. Smy, H. W. Sobel, V. Takhistov, A. Yankelevich, J. Hill, M. C. Jang, S. H. Lee, D. H. Moon, R. G. Park, B. S. Yang, B. Bodur, K. Scholberg, C. W. Walter, A. Beauchêne, O. Drapier, A. Ershova, Th. A. Mueller, A. D. Santos, P. Paganini, C. Quach, R. Rogly, T. Nakamura, J. S. Jang, R. P. Litchfield, L. N. Machado, F. J. P. Soler, J. G. Learned, K. Choi, N. Iovine, D. Tiwari, S. Cao, L. H. V. Anthony, D. Martin, N. W. Prouse, M. Scott, Y. Uchida, V. Berardi, N. F. Calabria, M. G. Catanesi, N. Ospina, E. Radicioni, A. Langella, G. De Rosa, G. Collazuol, M. Feltre, M. Mattiazzi, L. Ludovici. 2025-06-17. Search for neutron decay into an antineutrino and a neutral kaon in 0.401 megaton-years exposure of Super-Kamiokande. https://arxiv.org/abs/2506.14406

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