Search for two-neutrino double-beta decay of ¹³⁶Xe to the $$0$$$^{+}_{1}$$ excited state of ¹³⁶Ba with the complete EXO-200 dataset

Journal Article · 11 August 2023 · Chinese Physics C, High Energy Physics and Nuclear Physics

DOI: https://doi.org/10.1088/1674-1137/aceee3 · OSTI ID:1999522

Al Kharusi, S. ^[1]; Anton, G.; Badhrees, I.; Barbeau, P. S.; Beck, D.; Belov, V.; Bhatta, T.; Breidenbach, M.; Brunner, T.; Cao, G. F.; Cen, W. R.; Chambers, C.; Cleveland, B.; Coon, M.; Craycraft, A.; Daniels, T.; Darroch, L.; Daugherty, S. J.; Davis, J.; Delaquis, S. ; Der Mesrobian-Kabakian, A.; DeVoe, R.; Dilling, J.; Dolgolenko, A.; Dolinski, M. J.; Echevers, J.; Fairbank Jr., W.; Fairbank, D.; Farine, J.; Feyzbakhsh, S.; Fierlinger, P.; Fu, Y. S.; Fudenberg, D.; Gautam, P.; Gornea, R.; Gratta, G.; Hall, C.; Hansen, E. V.; Hoessl, J.; Hufschmidt, P.; Hughes, M.; Iverson, A.; Jamil, A.; Jessiman, C.; Jewell, M. J.; Johnson, A.; Karelin, A.; Kaufman, L. J.; Koffas, T.; Krücken, R.; Kuchenkov, A.; Kumar, K. S.; Lan, Y.; Larson, A.; Lenardo, B. G.; Leonard, D. S.; Li, G. S.; Li, S.; Li, Z.; Licciardi, C.; Lin, Y. H.; MacLellan, R.; McElroy, T.; Michel, T.; Mong, B.; Moore, D. C.; Murray, K.; Njoya, O.; Nusair, O.; Odian, A.; Ostrovskiy, I.; Perna, A.; Piepke, A.; Pocar, A.; Retière, F.; Robinson, A. L.; Rowson, P. C.; Runge, J.; Schmidt, S.; Sinclair, D.; Skarpaas, K.; Soma, A. K.; Stekhanov, V.; Tarka, M.; Thibado, S.; Todd, J.; Tolba, T.; Totev, T. I.; Tsang, R.; Veenstra, B.; Veeraraghavan, V.; Vogel, P.; Vuilleumier, J. -L.; Wagenpfeil, M.; Watkins, J.; Weber, M.; Wen, L. J.; Wichoski, U.; Wrede, G.; Wu, S. X.; Xia, Q.; Yahne, D. R.; Yang, L.; Yen, Y. -R.; Zeldovich, O. Ya.; Ziegler, T.

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1. IHEP Beijing

A new search for two-neutrino double-beta (2νββ) decay of 136Xe to the $$0_1^ + $$ excited state of ¹³⁶Ba is performed with the full EXO-200 dataset. A deep learning-based convolutional neural network is used to discriminate signal from background events. Signal detection efficiency is increased relative to previous searches by EXO-200 by more than a factor of two. With the addition of the Phase II dataset taken with an upgraded detector, the median 90% confidence level half-life sensitivity of 2νββ decay to the $$0_1^ + $$ state of ¹³⁶Ba is $$ 2.9 \times 10^{24} $$ yr using a total ¹³⁶Xe exposure of 234.1 kg yr. Furthermore, no statistically significant evidence for 2νββ decay to the $$0_1^ + $$ state is observed, leading to a lower limit of $$ T^{2\nu}_{1/2}(0^+ \rightarrow 0^+_1) \gt 1.4\times10^{24} $$ yr at 90% confidence level, improved by 70% relative to the current world's best constraint.

• Research Organization: University of Alabama, Tuscaloosa, AL (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Nuclear Physics (NP)
• Contributing Organization: EXO-200 Collaboration
• Grant/Contract Number: FG02-01ER41166
• OSTI ID: 1999522
• Journal Information: Chinese Physics C, High Energy Physics and Nuclear Physics, Journal Name: Chinese Physics C, High Energy Physics and Nuclear Physics Journal Issue: 10 Vol. 47; ISSN 1674-1137
• Publisher: IOP PublishingCopyright Statement
• Country of Publication: United States
• Language: English