1. Search for double-beta decay of 136Xe to excited states of 136Ba with the KamLAND-Zen experiment
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Collaboration, KamLAND-Zen, Asakura, K., Gando, A., Gando, Y., Hachiya, T., Hayashida, S., Ikeda, H., Inoue, K., Ishidoshiro, K., Ishikawa, T., Ishio, S., Koga, M., Matsuda, S., Mitsui, T., Motoki, D., Nakamura, K., Obara, S., Otani, M., Oura, T., Shimizu, I., Shirahata, Y., Shirai, J., Suzuki, A., Tachibana, H., Tamae, K., Ueshima, K., Watanabe, H., Xu, B. D., Yoshida, H., Kozlov, A., Takemoto, Y., Yoshida, S., Fushimi, K., Banks, T. I., Berger, B. E., Fujikawa, B. K., O'Donnell, T., Winslow, L. A., Efremenko, Y., Karwowski, H. J., Markoff, D. M., Tornow, W., Detwiler, J. A., Enomoto, S., and Decowski, M. P.
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High Energy Physics - Experiment ,Physics - Instrumentation and Detectors - Abstract
A search for double-beta decays of 136Xe to excited states of 136Ba has been performed with the first phase data set of the KamLAND-Zen experiment. The 0+1, 2+1 and 2+2 transitions of 0{\nu}\{beta}\{beta} decay were evaluated in an exposure of 89.5kg-yr of 136Xe, while the same transitions of 2{\nu}\{beta}\{beta} decay were evaluated in an exposure of 61.8kg-yr. No excess over background was found for all decay modes. The lower half-life limits of the 2+1 state transitions of 0{\nu}\{beta}\{beta} and 2{\nu}\{beta}\{beta} decay were improved to T(0{\nu}, 0+ \rightarrow 2+) > 2.6\times10^25 yr and T(2{\nu}, 0+ \rightarrow 2+) > 4.6\times10^23 yr (90% C.L.), respectively. We report on the first experimental lower half-life limits for the transitions to the 0+1 state of 136Xe for 0{\nu}\{beta}\{beta} and 2{\nu}\{beta}\{beta} decay. They are T (0{\nu}, 0+ \rightarrow 0+) > 2.4\times10^25 yr and T(2{\nu}, 0+ \rightarrow 0+) > 8.3\times10^23 yr (90% C.L.). The transitions to the 2+2 states are also evaluated for the first time to be T(0{\nu}, 0+ \rightarrow 2+) > 2.6\times10^25 yr and T(2{\nu}, 0+ \rightarrow 2+) > 9.0\times10^23 yr (90% C.L.). These results are compared to recent theoretical predictions., Comment: 16 pages, 4 figures. Published in Nuclear Physics A
- Published
- 2015
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