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arXiv · 1912.05761

Results of the MAJORANA DEMONSTRATOR's Search for Double-Beta Decay of $^{76}$Ge to Excited States of $^{76}$Se

I. S. Guinn·I. J. Arnquist·F. T. Avignone III·A. S. Barabash·C. J. Barton·F. E. Bertrand·B. Bos·M. Busch·M. Buuck·T. S. Caldwell·Y-D. Chan·C. D. Christofferson·P-H. Chu·M. L. Clark·C. Cuesta·J. A. Detwiler·A. Drobizhev·D. W. Edwins·Yu. Efremenko·H. Ejiri·S. R. Elliott·T. Gilliss·G. K. Giovanetti·M. P. Green·J. Gruszko·V. E. Guiseppe·C. R. Haufe·R. J. Hegedus·R. Henning·D. Hervas Aguilar·E. W. Hoppe·A. Hostiuc·M. F. Kidd·I. Kim·R. T. Kouzes·A. M. Lopez·J. M. López-Casta no·E. L. Martin·R. D. Martin·R. Massarczyk·S. J. Meijer·S. Mertens·J. Myslik·T. K. Oli·G. Othman·W. Pettus·A. W. P. Poon·D. C. Radford·J. Rager·A. L. Reine·K. Rielage·N. W. Ruof·M. J. Stortini·D. Tedeschi·R. L. Varner·J. F. Wilkerson·C. Wiseman·W. Xu·C. -H. Yu·B. X. Zhu
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Abstract

The MAJORANA DEMONSTRATOR is searching for double-beta decay of $^{76}$Ge to excited states (E.S.) in $^{76}$Se using a modular array of high purity Germanium detectors. $^{76}$Ge can decay into three E.S.s of $^{76}$Se. The E.S. decays have a clear event signature consisting of a $\beta\beta$-decay with the prompt emission of one or two $\gamma$-rays, resulting in with high probability in a multi-site event. The granularity of the DEMONSTRATOR detector array enables powerful discrimination of this event signature from backgrounds. Using 21.3 kg-y of isotopic exposure, the DEMONSTRATOR has set world leading limits for each E.S. decay, with 90% CL lower half-life limits in the range of $(0.56-2.1)\cdot10^{24}$ y. In particular, for the $2\nu$ transition to the first $0^+$ E.S. of $^{76}$Se, a lower half-life limit of $0.68\cdot10^{24}$ at 90% CL was achieved.

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I. S. Guinn, I. J. Arnquist, F. T. Avignone III, A. S. Barabash, C. J. Barton, F. E. Bertrand, B. Bos, M. Busch, M. Buuck, T. S. Caldwell, Y-D. Chan, C. D. Christofferson, P-H. Chu, M. L. Clark, C. Cuesta, J. A. Detwiler, A. Drobizhev, D. W. Edwins, Yu. Efremenko, H. Ejiri, S. R. Elliott, T. Gilliss, G. K. Giovanetti, M. P. Green, J. Gruszko, V. E. Guiseppe, C. R. Haufe, R. J. Hegedus, R. Henning, D. Hervas Aguilar, E. W. Hoppe, A. Hostiuc, M. F. Kidd, I. Kim, R. T. Kouzes, A. M. Lopez, J. M. López-Casta no, E. L. Martin, R. D. Martin, R. Massarczyk, S. J. Meijer, S. Mertens, J. Myslik, T. K. Oli, G. Othman, W. Pettus, A. W. P. Poon, D. C. Radford, J. Rager, A. L. Reine, K. Rielage, N. W. Ruof, M. J. Stortini, D. Tedeschi, R. L. Varner, J. F. Wilkerson, C. Wiseman, W. Xu, C. -H. Yu, B. X. Zhu. 2019-12-12. Results of the MAJORANA DEMONSTRATOR's Search for Double-Beta Decay of $^{76}$Ge to Excited States of $^{76}$Se. https://doi.org/10.1088/1742-6596%2F1468%2F1%2F012115

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