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Adhikari2021_Article_Pulse-shapeDiscriminationAgain.pdf (2.3 MB)

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

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posted on 2023-06-10, 02:20 authored by P Adhikari, R Ajaj, M Alpízar-Venegas, P A Amaudruz, D J Auty, M Batygov, B Beltran, H Benmansour, C E Bina, J Bonatt, W Bonivento, M G Boulay, B Broerman, J F Bueno, Simon PeetersSimon Peeters, DEAP Collaboration, others
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 39Ar 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.

History

Publication status

  • Published

File Version

  • Published version

Journal

European Physical Journal C: Particles and Fields

ISSN

1434-6044

Publisher

Springer

Issue

9

Volume

81

Page range

1-13

Article number

a823

Event location

France

Department affiliated with

  • Physics and Astronomy Publications

Full text available

  • Yes

Peer reviewed?

  • Yes

Legacy Posted Date

2022-01-17

First Open Access (FOA) Date

2022-01-17

First Compliant Deposit (FCD) Date

2022-01-17

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