Limit on neutrinoless ββ decay of 136Xe from the first phase of KamLAND-Zen and comparison with the positive claim in 76Ge.
We present results from the first phase of the KamLAND-Zen double-beta decay experiment, corresponding to an exposure of 89.5 kg yr of (136)Xe. We obtain a lower limit for the neutrinoless double-beta decay half-life of T(1/2)(0ν)>1.9×10(25) yr at 90% C.L. The combined results from KamLAND-Zen and EXO-200 give T(1/2)(0ν)>3.4×10(25) yr at 90% C.L., which corresponds to a Majorana neutrino mass limit of <(120-250) meV based on a representative range of available matrix element calculations. Using those calculations, this result excludes the Majorana neutrino mass range expected from the neutrinoless double-beta decay detection claim in (76)Ge, reported by a part of the Heidelberg-Moscow Collaboration, at more than 97.5% C.L.
Gando, A; Gando, Y; Hanakago, H; Ikeda, H; Inoue, K; Ishidoshiro, K; Kato, R; Koga, M; Matsuda, S; Mitsui, T; Motoki, D; Nakada, T; Nakamura, K; Obata, A; Oki, A; Ono, Y; Otani, M; Shimizu, I; Shirai, J; Suzuki, A; Takemoto, Y; Tamae, K; Ueshima, K; Watanabe, H; Xu, BD; Yamada, S; Yoshida, H; Kozlov, A; Yoshida, S; Banks, TI; Freedman, SJ; Fujikawa, BK; Han, K; O'Donnell, T; Berger, BE; Efremenko, Y; Karwowski, HJ; Markoff, DM; Tornow, W; Detwiler, JA; Enomoto, S; Decowski, MP; KamLAND-Zen Collaboration,
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