Direct measurement of the $$^{39}$$Ar half-life from 3.4 years of data with the DEAP-3600 detector

Adhikari, P.; Ajaj, R.; Alpízar-Venegas, M.; Amaudruz, P. -A.; Anstey, J.; Auty, D. J.; Batygov, M.; Beltran, B.; Bigentini, M. A.; Bina, C. E.; Bonivento, W. M.; Boulay, M. G.; Bueno, J. F.; Cadeddu, M.; Cai, B.; Cárdenas-Montes, M.; Cavuoti, S.; Chen, Y.; Choudhary, S.; Cleveland, B. T.; Crampton, R.; Daugherty, S.; Delgobbo, P.; Stefano, P. Di; 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.; García Abia, P.; 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.; Khoshraftar Yazdi, M.; Kuźniak, M.; La Zia, F.; Lai, M.; Langrock, S.; Lehnert, B.; LePage-Bourbonnais, J.; 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.; Rodríguez García, I.; 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.; Turcotte-Tardif, R.; Vázquez-Jáuregui, E.; Viel, S.; Vyas, B.; Walczak, M.; Walding, J.; Ward, M.; Westerdale, S.; Wormington, R.; Zuñiga-Reyes, A.; Null, Null

doi:10.1140/epjc/s10052-025-14289-5

The half-life of 39Ar is measured using the DEAP-3600 detector located 2 km underground at SNOLAB. Between 2016 and 2020, DEAP-3600 used a target mass of (3269 ± 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 39Ar 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 powerful discrimination between nuclear recoils and electron recoils, resulting in the selection of a clean sample of 39Ar decays. Observing over a period of 3.4 years, the 39Ar half-life is measured to be (302±8stat±6sys) years. This new direct measurement suggests that the half-life of 39Ar is significantly longer than the accepted value, with potential implications for measurements using this isotope’s half-life as input.

Direct measurement of the $$^{39}$$Ar half-life from 3.4 years of data with the DEAP-3600 detector / Adhikari, P.; Ajaj, R.; Alpízar-Venegas, M.; Amaudruz, P. -A.; Anstey, J.; Auty, D. J.; Batygov, M.; Beltran, B.; Bigentini, M. A.; Bina, C. E.; Bonivento, W. M.; Boulay, M. G.; Bueno, J. F.; Cadeddu, M.; Cai, B.; Cárdenas-Montes, M.; Cavuoti, S.; Chen, Y.; Choudhary, S.; Cleveland, B. T.; Crampton, R.; Daugherty, S.; Delgobbo, P.; Stefano, P. Di; 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.; García Abia, P.; 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.; Khoshraftar Yazdi, M.; Kuźniak, M.; La Zia, F.; Lai, M.; Langrock, S.; Lehnert, B.; LePage-Bourbonnais, J.; 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.; Rodríguez García, I.; 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.; Turcotte-Tardif, R.; Vázquez-Jáuregui, E.; Viel, S.; Vyas, B.; Walczak, M.; Walding, J.; Ward, M.; Westerdale, S.; Wormington, R.; Zuñiga-Reyes, A.; Null, Null. - In: EUROPEAN PHYSICAL JOURNAL. C, PARTICLES AND FIELDS. - ISSN 1434-6052. - 85:7(2025). [10.1140/epjc/s10052-025-14289-5]