Electromagnetic backgrounds and potassium-42 activity in the DEAP-3600 dark matter detector

Ajaj, Rahaf; Araujo, G. R.; Batygov, M.; Beltrán, B.; Bina, C. E.; Boulay, M. G.; Broerman, B.; Bueno, J. F.; Burghardt, P. M.; Butcher, A.; Cai, B.; Cárdenas‐Montes, Miguel; Cavuoti, S.; Chen, M.; Chen, Y.; Cleveland, B. T.; Dering, K.; Duncan, F. A.; Dunford, M.; Erlandson, A.; Fatemighomi, N.; Fiorillo, G.; Flower, A.; Ford, R.; Gagnon, R.; Gallacher, D.; Abia, P. García; Garg, Sakshi; Giampa, P.; Goeldi, D.; Golovko, V. V.; Gorel, P.; Graham, K.; Grant, D.; Hallin, A. L.; Hamstra, M.; Harvey, P. J.; Hearns, C.; Joy, A.; Jillings, C.; Kamaev, O.; Kaur, G.; Kemp, A.; Kochanek, I.; Kuźniak, M.; Langrock, S.; Zia, F. La; Lehnert, B.; Li, X.; Litvinov, O.; Lock, James A.; Longo, Giuseppe; Majewski, P.; McDonald, A. B.; McElroy, Thomas; McGinn, T.; McLaughlin, J.; Mehdiyev, R.; Mielnichuk, C.; Monroe, J.; Nadeau, P.; Nantais, C.; Ng, C.; Noble, A. J.; Ouellet, C.; Pasuthip, P.; Peeters, S. J. M.; Pesudo, V.; Piro, M.‐C.; Pollmann, T. R.; Rand, E. T.; Rethmeier, C.; Retière, F.; García, E.; Santorelli, R.; Seeburn, N.; Skensved, P.; Smith, B. C.; Smith, N. J. T.; Sonley, T. J.; Stainforth, R.; Stone, Connor; Strickland, V.; Sur, B.; Vázquez‐Jáuregui, E.; Veloce, L. M.; Viel, S.; Walding, J.; Waqar, Moaz; Ward, M.; Westerdale, S.; Willis, J. L.; Zuñiga-Reyes, A.

doi:10.1103/physrevd.100.072009

Cited by 33 publications

(42 citation statements)

References 22 publications

(2 reference statements)

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“…The data used in this work was taken between November 2016 and March 2020 for an exposure of 4.5 tonneyears after event position cuts. The vast majority of recorded events are from 39 Ar β-decays, with a small contribution of γ 's from radioactivity in detector materials [19]. The dataset contains both blinded and unblinded data.…”

Section: Data Selectionmentioning

confidence: 99%

Pulse-shape discrimination against low-energy Ar-39 beta decays in liquid argon with 4.5 tonne-years of DEAP-3600 data

Adhikari¹,

Ajaj²,

Alpízar-Venegas³

et al. 2021

Eur. Phys. J. C

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The DEAP-3600 detector searches for the scintillation signal from dark matter particles scattering on a 3.3 tonne liquid argon target. The largest background comes from $$^{39}\text{ Ar }$$ 39 Ar beta decays and is suppressed using pulse-shape discrimination (PSD). We use two types of PSD estimator: the prompt-fraction, which considers the fraction of the scintillation signal in a narrow and a wide time window around the event peak, and the log-likelihood-ratio, which compares the observed photon arrival times to a signal and a background model. We furthermore use two algorithms to determine the number of photons detected at a given time: (1) simply dividing the charge of each PMT pulse by the mean single-photoelectron charge, and (2) a likelihood analysis that considers the probability to detect a certain number of photons at a given time, based on a model for the scintillation pulse shape and for afterpulsing in the light detectors. The prompt-fraction performs approximately as well as the log-likelihood-ratio PSD algorithm if the photon detection times are not biased by detector effects. We explain this result using a model for the information carried by scintillation photons as a function of the time when they are detected.

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Section: Data Selectionmentioning

confidence: 99%

Pulse-shape discrimination against low-energy Ar-39 beta decays in liquid argon with 4.5 tonne-years of DEAP-3600 data

Adhikari¹,

Ajaj²,

Alpízar-Venegas³

et al. 2021

Eur. Phys. J. C

Self Cite

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“…There are two mechanisms for the production of 42 Ar in atmospheric argon: a two-step neutron capture (requiring a high neutron flux because of the half-life of 41 Ar, being of 1.8 h) and the (α,2p) reaction on 40 Ar. The specific activity of 42 Ar has been studied in the context of different experiments using argon like ICARUS [212], DBA giving 92 +22 −46 µBq/kg [213] and, more recently, DEAP, measuring 40.4 ± 5.9 µBq/kg [214].…”

Section: Argonmentioning

confidence: 99%

“…The latter is a β − emitter with a transition energy of 565 keV and half-life of 269 y; 39 Ar is mainly generated by the 40 Ar(n,2n) 39 Ar reaction started by cosmic neutrons. The typical activity of 39 Ar in atmospheric argon is around one Bq/kg, as quantified by WARP [215] and DEAP [214]. However, after a campaign of extracting and purifying argon from deep CO 2 wells in Colorado, USA, the DarkSide-50 experiment (operating a two-phase liquid argon TPC at LNGS) presented results from the use of this underground argon for the first time; the measured activity of 39 Ar was (0.73 ± 0.11) mBq/kg, which means a reduction of a factor 1400 relative to the atmospheric argon [216].…”

Section: Argonmentioning

confidence: 99%

Cosmogenic Activation in Double Beta Decay Experiments

Cebrián

2020

Universe

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Double beta decay is a very rare nuclear process and, therefore, experiments intended to detect it must be operated deep underground and in ultra-low background conditions. Long-lived radioisotopes produced by the previous exposure of materials to cosmic rays on the Earth’s surface or even underground can become problematic for the required sensitivity. Here, the studies developed to quantify and reduce the activation yields in detectors and materials used in the set-up of these experiments will be reviewed, considering target materials like germanium, tellurium and xenon together with other ones commonly used like copper, lead, stainless steel or argon. Calculations following very different approaches and measurements from irradiation experiments using beams or directly cosmic rays will be considered for relevant radioisotopes. The effect of cosmogenic activation in present and future double beta decay projects based on different types of detectors will be analyzed too.

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“…A future direction that is being investigated in the DEAP-3600 collaboration is whether is it worth replacing the atmospheric argon in the detector with low radioactivity underground argon for the remainder of the experiments life time. The specific activity of low radio activity underground argon is 6.6 mBq/kg [53], which is ∼144 times lower then the current specific activity of 0.95 Bq/kg [51]. If the atmospheric argon was replace with underground argon, the total trigger rate do to 39 Ar would be reduced to 22 Hz as well as the the pile-up rate due to 39 Ar- 39 Ar coincidence trigger would reduce to 7.5 mHz.…”

Section: Background Studymentioning

confidence: 80%

“…Both of these decays are capable of producing Cherenkov radiation in both the PMT glass and the acrylic. The qPE spectra of Cherenkov produced by 40 To get the total Cherenkov rate based on all of the decays discussed above, the histograms can be scaled by their respective branching ratios and then by the rate of decay that has been measured in DEAP-3600 [51]. The sum of all of the contributions normalized to the rate can be seen in Figure 4.17.…”

Section: Cherenkov Eventsmentioning

confidence: 99%

Low-Energy Threshold Analysis Using the DEAP-3600 Dark Matter Detector

Lock¹

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DEAP-3600 is a single-phase liquid argon WIMP detector located 2 km underground in the SNOLAB research facility. DEAP-3600 is searching for dark matter; an elusive form of matter that was first postulated in the early 20 th century, but has not yet been found. The goal of the following work is to perform a low mass WIMP search. A low mass WIMP search is made possible by lowering the energy threshold of the hardware trigger from 1000 ADC to 150 ADC. Low energy events in the detector are characterized as Cherenkov radiation, low energy retriggers, or high energy retriggers; all of which are background events. The final data set has a live time of 2.10 days and an exposure of 4.41 × 10 3 kg • days using a LAr target mass of (3279±97)kg. The results from the low mass WIMP search is a WIMP-nucleon spin independent cross-section of 3.96 × 10 −42 cm 2 at a 90% CL corresponding to WIMPs with a mass of 55 GeV/c 2. i Lastly, the people I owe the most thanks to; I would like to thank my family, Dad, Sarah, and Chris for all of their support and love over the course of my entire academic career, it would not have been possible without you guys. I would also like to thank Deb, Scarlett, Santana, and Barry for their support as well. To Caidence, I'll never understand how you managed to juggle a masters, full time job, part time job, and life; and also dealt with me and everything I was going through. Even with all of this happening you always provided me with constant love and support; I can never express how much this means to me. You've stayed with me through four years apart for undergrad, and now through this; now that it's over I can't wait to start the next chapter of our lives and see what comes next! iii

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Electromagnetic backgrounds and potassium-42 activity in the DEAP-3600 dark matter detector

Abstract: al. (2019) Electromagnetic backgrounds and potassium-42 activity in the DEAP-3600 dark matter detector. Physical Review D, 100 (7). pp. 1-17.

Cited by 33 publications

References 22 publications

Pulse-shape discrimination against low-energy Ar-39 beta decays in liquid argon with 4.5 tonne-years of DEAP-3600 data

Pulse-shape discrimination against low-energy Ar-39 beta decays in liquid argon with 4.5 tonne-years of DEAP-3600 data

Cosmogenic Activation in Double Beta Decay Experiments

Low-Energy Threshold Analysis Using the DEAP-3600 Dark Matter Detector

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