Direct Measurement of the $^{39}$Ar Half-life from 3.4 Years of Data with the DEAP-3600 Detector

• DOI: 10.48550/arxiv.2501.13196
• Publication Date: 2025-01-01
• Authors: DEAP Collaboration; Adhikari, P.; Ajaj, R.; Alpízar-Venegas, M.; Amaudruz, P. -A.; Anstey, J.; Auty, D. J.; Batygov, M.; Beltran, B.; Bina, C. E.; Bonivento, W. M.; Boulay, M. G.; Bueno, J. F.; Cadeddu, M.; Cai, B.; Cárdenas-Montes, M.; Chen, Y.; Choudhary, S.; Cleveland, B. T.; Crampton, R.; Daugherty, S.; DelGobbo, P.; Di Stefano, P.; Dolganov, G.; Doria, L.; Duncan, F. A.; Dunford, M.; Ellingwood, E.; Erlandson, A.; Farahani, S. S.; Fatemighomi, N.; Fiorillo, G.; Ford, R. J.; Gahan, D.; Gallacher, D.; Garai, A.; Abia, P. García; Garg, S.; Giampa, P.; Giménez-Alcázar, A.; Goeldi, D.; Golovko, V. V.; Gorel, P.; Graham, K.; Grobov, A.; Hallin, A. L.; Hamstra, M.; Haskins, S.; Hu, J.; Hucker, J.; Hugues, T.; Ilyasov, A.; Jigmeddorj, B.; Jillings, C. J.; Joy, A.; Kaur, G.; Kemp, A.; Yazdi, M. Khoshra...; Kuźniak, M.; La Zia, F.; Lai, M.; Langrock, S.; Lehnert, B.; LePage-Bourbonnai...; Levashko, N.; Lissia, M.; Luzzi, L.; Machulin, I.; Maru, A.; Mason, J.; McDonald, A. B.; McElroy, T.; McLaughlin, J. B.; Mielnichuk, C.; Mirasola, L.; Moharana, A.; Monroe, J.; Murray, A.; Ng, C.; Oliviéro, G.; Olszewski, M.; Pal, S.; Papi, D.; Park, B.; Perry, M.; Pesudo, V.; Pollmann, T. R.; Rad, F.; Rethmeier, C.; Retière, F.; García, I. Rodríguez; Roszkowski, L.; Santorelli, R.; Schuckman II, F. G.; Seth, S.; Shalamova, V.; Skensved, P.; Smirnova, T.; Sobotkiewich, K.; Sonley, T.; Sosiak, J.; Soukup, J.; Stainforth, R.; Stringer, M.; Tang, J.; Vázquez-Jáuregui, E.; Viel, S.; Vyas, B.; Walczak, M.; Walding, J.; Ward, M.; Westerdale, S.; Wormington, R.; Zuñiga-Reyes, A.
• Keywords: Physics - Instrumentation and Detectors; FOS: Physical sciences; Instrumentation and Detectors (physics.ins-det); Nuclear Experiment (nucl-ex); Nuclear Experiment

11 pages, 8 figures<br/>The half-life of $^{39}$Ar is measured using the DEAP-3600 detector located 2 km underground at SNOLAB. In 2016-2020, DEAP-3600 used a target mass of (3269 $\pm$ 24) kg of liquid argon distilled from the atmosphere in a direct-detection dark matter search. Such an argon mass also enables direct measurements of argon isotope properties. The decay of $^{39}$Ar in DEAP-3600 is the dominant source of triggers by two orders of magnitude, ensuring high statistics and making DEAP-3600 well-suited for measuring this isotope's half-life. Use of the pulse-shape discrimination technique in DEAP-3600 allows for powerful discrimination between nuclear recoils and electron recoils, resulting in the selection of a clean sample of $^{39}$Ar decays. Observing over a period of 3.4 years, the $^{39}$Ar half-life is measured to be $(302 \pm 8_{\rm stat} \pm 6_{\rm sys})$ years. This new direct measurement suggests that the half-life of $^{39}$Ar may be significantly longer than the accepted value, with potential implications for measurements using this isotope's half-life as input.<br/>