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arXiv · 2406.11438

Search for Majorana Neutrinos with the Complete KamLAND-Zen Dataset

S. Abe·T. Araki·K. Chiba·T. Eda·M. Eizuka·Y. Funahashi·A. Furuto·A. Gando·Y. Gando·S. Goto·T. Hachiya·K. Hata·K. Ichimura·S. Ieki·H. Ikeda·K. Inoue·K. Ishidoshiro·Y. Kamei·N. Kawada·Y. Kishimoto·M. Koga·A. Marthe·Y. Matsumoto·T. Mitsui·H. Miyake·D. Morita·R. Nakajima·K. Nakamura·R. Nakamura·J. Nakane·T. Ono·H. Ozaki·K. Saito·T. Sakai·I. Shimizu·J. Shirai·K. Shiraishi·A. Suzuki·K. Tachibana·K. Tamae·H. Watanabe·K. Watanabe·S. Yoshida·S. Umehara·K. Fushimi·K. Kotera·Y. Urano·B. E. Berger·B. K. Fujikawa·J. G. Learned·J. Maricic·Z. Fu·S. Ghosh·J. Smolsky·L. A. Winslow·Y. Efremenko·H. J. Karwowski·D. M. Markoff·W. Tornow·S. Dell'Oro·T. O'Donnell·J. A. Detwiler·S. Enomoto·M. P. Decowski·K. M. Weerman·C. Grant·O. Penek·H. Song·A. Li·S. N. Axani·M. Garcia·M. Sarfraz
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Abstract

We present a search for neutrinoless double-beta ($0\nu\beta\beta$) decay of $^{136}$Xe using the full \mbox{KamLAND-Zen 800} dataset with 745\,kg of enriched xenon, corresponding to an exposure of $2.1$\,ton\,yr of $^{136}$Xe. This updated search benefits from a more than twofold increase in exposure, recovery of photo-sensor gain, and reduced background from muon-induced spallation of xenon. Combining with the search in the previous KamLAND-Zen phase, we obtain a lower limit for the $0\nu\beta\beta$ decay half-life of $T_{1/2}^{0\nu} > 3.8 \times 10^{26}$\,yr at 90\% C.L., a factor of 1.7 improvement over the previous limit. The corresponding upper limits on the effective Majorana neutrino mass are in the range 28--122\,meV using phenomenological nuclear matrix element calculations.

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S. Abe, T. Araki, K. Chiba, T. Eda, M. Eizuka, Y. Funahashi, A. Furuto, A. Gando, Y. Gando, S. Goto, T. Hachiya, K. Hata, K. Ichimura, S. Ieki, H. Ikeda, K. Inoue, K. Ishidoshiro, Y. Kamei, N. Kawada, Y. Kishimoto, M. Koga, A. Marthe, Y. Matsumoto, T. Mitsui, H. Miyake, D. Morita, R. Nakajima, K. Nakamura, R. Nakamura, J. Nakane, T. Ono, H. Ozaki, K. Saito, T. Sakai, I. Shimizu, J. Shirai, K. Shiraishi, A. Suzuki, K. Tachibana, K. Tamae, H. Watanabe, K. Watanabe, S. Yoshida, S. Umehara, K. Fushimi, K. Kotera, Y. Urano, B. E. Berger, B. K. Fujikawa, J. G. Learned, J. Maricic, Z. Fu, S. Ghosh, J. Smolsky, L. A. Winslow, Y. Efremenko, H. J. Karwowski, D. M. Markoff, W. Tornow, S. Dell'Oro, T. O'Donnell, J. A. Detwiler, S. Enomoto, M. P. Decowski, K. M. Weerman, C. Grant, O. Penek, H. Song, A. Li, S. N. Axani, M. Garcia, M. Sarfraz. 2024-06-17. Search for Majorana Neutrinos with the Complete KamLAND-Zen Dataset. https://doi.org/10.1103/jkf6-48j8

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