1. Constraints on the decay of $^{180m}$Ta
- Author
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Arnquist, I. J., Avignone III, F. T., Barabash, A. S., Barton, C. J., Bhimani, K. H., Blalock, E., Bos, B., Busch, M., Buuck, M., Caldwell, T. S., Christofferson, C. D., Chu, P. -H., Clark, M. L., Cuesta, C., Detwiler, J. A., Efremenko, Yu., Ejiri, H., Elliott, S. R., Giovanetti, G. K., Goett, J., Green, M. P., Gruszko, J., Guinn, I. S., Guiseppe, V. E., Haufe, C. R., Henning, R., Aguilar, D. Hervas, Hoppe, E. W., Hostiuc, A., Kim, I., Kouzes, R. T., Lannen V, T. E., Li, A., Lopez-Castano, J. M., Massarczyk, R., Meijer, S. J., Meijer, W., Oli, T. K., Paudel, L. S., Pettus, W., Poon, A. W. P., Radford, D. C., Reine, A. L., Rielage, K., Rouyer, A., Ruof, N. W., Schaper, D. C., Schleich, S. J., Smith-Gandy, T. A., Tedeschi, D., Varner, R. L., Vasilyev, S., Watkins, S. L., Wilkerson, J. F., Wiseman, C., Xu, W., Yu, C. -H., Alves, D. S. M., and Ramani, H.
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Nuclear Experiment ,High Energy Physics - Experiment - Abstract
$^{180m}$Ta is a rare nuclear isomer whose decay has never been observed. Its remarkably long lifetime surpasses the half-lives of all other known $\beta$ and electron capture decays due to the large K-spin differences and small energy differences between the isomeric and lower energy states. Detecting its decay presents a significant experimental challenge but could shed light on neutrino-induced nucleosynthesis mechanisms, the nature of dark matter and K-spin violation. For this study, we repurposed the MAJORANA DEMONSTRATOR, an experimental search for the neutrinoless double-beta decay of $^{76}$Ge using an array of high-purity germanium detectors, to search for the decay of $^{180m}$Ta. More than 17 kilograms, the largest amount of tantalum metal ever used for such a search was installed within the ultra-low background detector array. In this paper we present results from the first year of Ta data taking and provide an updated limit for the $^{180m}$Ta half-life on the different decay channels. With new limits up to 1.5 x $10^{19}$ years, we improved existing limits by one to two orders of magnitude. This result is the most sensitive search for a single $\beta$ and electron capture decay ever achieved.
- Published
- 2023
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