Eur. Phys. J. C (2023) 83: 642
https://doi.org/10.1140/epjc/s10052-023-11678-6

Regular Article - Experimental Physics

Precision measurement of the specific activity of Ar in atmospheric argon with the DEAP-3600 detector

¹ Department of Physics, University of Alberta, T6G 2R3, Edmonton, AB, Canada
² AstroCeNT, Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, Rektorska 4, 00-614, Warsaw, Poland
³ Physics Department, Università degli Studi di Cagliari, 09042, Cagliari, Italy
⁴ Canadian Nuclear Laboratories, Chalk River, K0J 1J0, Ontario, Canada
⁵ Department of Physics and Astronomy, University of California, 92507, Riverside, CA, USA
⁶ Department of Physics, Carleton University, K1S 5B6, Ottawa, ON, Canada
⁷ Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas, 28040, Madrid, Spain
⁸ Physics Department, Università degli Studi “Federico II” di Napoli, 80126, Naples, Italy
⁹ Astronomical Observatory of Capodimonte, Salita Moiariello 16, 80131, Naples, Italy
¹⁰ INFN Cagliari, 09042, Cagliari, Italy
¹¹ INFN Laboratori Nazionali del Gran Sasso, 67100, Assergi, AQ, Italy
¹² INFN Napoli, 80126, Naples, Italy
¹³ School of Natural Sciences, Laurentian University, P3E 2C6, Sudbury, ON, Canada
¹⁴ Nuclear Science Division, Lawrence Berkeley National Laboratory, 94720, Berkeley, CA, USA
¹⁵ Instituto de Física, Universidad Nacional Autónoma de México, A. P. 20-364, 01000, Mexico City, Mexico
¹⁶ BP2, National Centre for Nuclear Research, ul. Pasteura 7, 02-093, Warsaw, Poland
¹⁷ National Research Centre Kurchatov Institute, 123182, Moscow, Russia
¹⁸ National Research Nuclear University MEPhI, 115409, Moscow, Russia
¹⁹ Physics Department, Princeton University, 08544, Princeton, NJ, USA
²⁰ PRISMA+ Cluster of Excellence and Institut für Kernphysik, Johannes Gutenberg-Universität Mainz, 55128, Mainz, Germany
²¹ Department of Physics, Engineering Physics and Astronomy, Queen’s University, K7L 3N6, Kingston, ON, Canada
²² Royal Holloway University London, Egham Hill, TW20 0EX, Egham, Surrey, UK
²³ Rutherford Appleton Laboratory, Harwell Oxford, OX11 0QX, Didcot, UK
²⁴ SNOLAB, P3Y 1M3, Lively, ON, Canada
²⁵ University of Sussex, Sussex House, BN1 9RH, Brighton, East Sussex, UK
²⁶ TRIUMF, V6T 2A3, Vancouver, BC, Canada
²⁷ Department of Physics, Technische Universität München, 80333, Munich, Germany
²⁸ Arthur B. McDonald Canadian Astroparticle Physics Research Institute, Queen’s University, K7L 3N6, Kingston, ON, Canada
²⁹ Currently at SNOLAB, P3Y 1M3, Lively, ON, Canada
³⁰ Currently at Nikhef and the University of Amsterdam, 1098 XG, Science Park, Amsterdam, The Netherlands

^fq deap-papers@snolab.ca

Received: 27 February 2023
Accepted: 4 June 2023
Published online: 20 July 2023

Abstract

The specific activity of the decay of Ar in atmospheric argon is measured using the DEAP-3600 detector. DEAP-3600, located 2 km underground at SNOLAB, uses a total of (3269 ± 24) kg of liquid argon distilled from the atmosphere to search for dark matter. This detector is well-suited to measure the decay of Ar owing to its very low background levels. This is achieved in two ways: it uses low background construction materials; and it uses pulse-shape discrimination to differentiate between nuclear recoils and electron recoils. With 167 live-days of data, the measured specific activity at the time of atmospheric extraction is (0.964 ± 0.001 ± 0.024) Bq/kg, which is consistent with results from other experiments. A cross-check analysis using different event selection criteria and a different statistical method confirms the result.