Electromagnetic Backgrounds and Potassium-42 Activity in the DEAP-3600 Dark Matter Detector. (arXiv:1905.05811v1 [nucl-ex])

Electromagnetic Backgrounds and Potassium-42 Activity in the DEAP-3600 Dark Matter Detector. (arXiv:1905.05811v1 [nucl-ex])
(DEAP Collaboration), <a href="http://arxiv.org/find/nucl-ex/1/au:+Ajaj_R/0/1/0/all/0/1">R. Ajaj</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Araujo_G/0/1/0/all/0/1">G. R. Araujo</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Batygov_M/0/1/0/all/0/1">M. Batygov</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Beltran_B/0/1/0/all/0/1">B. Beltran</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Bina_C/0/1/0/all/0/1">C. E. Bina</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Boulay_M/0/1/0/all/0/1">M. G. Boulay</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Broerman_B/0/1/0/all/0/1">B. Broerman</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Bueno_J/0/1/0/all/0/1">J. F. Bueno</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Burghardt_P/0/1/0/all/0/1">P. M. Burghardt</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Butcher_A/0/1/0/all/0/1">A. Butcher</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Cardenas_Montes_M/0/1/0/all/0/1">M. Cárdenas-Montes</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Cavuoti_S/0/1/0/all/0/1">S. Cavuoti</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Chen_M/0/1/0/all/0/1">M. Chen</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Chen_Y/0/1/0/all/0/1">Y. Chen</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Cleveland_B/0/1/0/all/0/1">B. T. Cleveland</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Dering_K/0/1/0/all/0/1">K. Dering</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Duncan_F/0/1/0/all/0/1">F. A. Duncan</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Dunford_M/0/1/0/all/0/1">M. Dunford</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Erlandson_A/0/1/0/all/0/1">A. Erlandson</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Fatemighomi_N/0/1/0/all/0/1">N. Fatemighomi</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Fiorillo_G/0/1/0/all/0/1">G. Fiorillo</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Flower_A/0/1/0/all/0/1">A. Flower</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Ford_R/0/1/0/all/0/1">R. J. Ford</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Gallacher_D/0/1/0/all/0/1">D. Gallacher</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Abia_P/0/1/0/all/0/1">P. García Abia</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Garg_S/0/1/0/all/0/1">S. Garg</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Giampa_P/0/1/0/all/0/1">P. Giampa</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Goeldi_D/0/1/0/all/0/1">D. Goeldi</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Golovko_V/0/1/0/all/0/1">V. V. Golovko</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Gorel_P/0/1/0/all/0/1">P. Gorel</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Graham_K/0/1/0/all/0/1">K. Graham</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Grant_D/0/1/0/all/0/1">D. R. Grant</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Hallin_A/0/1/0/all/0/1">A. L. Hallin</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Hamstra_M/0/1/0/all/0/1">M. Hamstra</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Harvey_P/0/1/0/all/0/1">P. J. Harvey</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Hearns_C/0/1/0/all/0/1">C. Hearns</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Joy_A/0/1/0/all/0/1">A. Joy</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Jillings_C/0/1/0/all/0/1">C. J. Jillings</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Kamaev_O/0/1/0/all/0/1">O. Kamaev</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Kaur_G/0/1/0/all/0/1">G. Kaur</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Kemp_A/0/1/0/all/0/1">A. Kemp</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Kochanek_I/0/1/0/all/0/1">I. Kochanek</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Kuzniak_M/0/1/0/all/0/1">M. Kuźniak</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Langrock_S/0/1/0/all/0/1">S. Langrock</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Zia_F/0/1/0/all/0/1">F. La Zia</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Lehnert_B/0/1/0/all/0/1">B. Lehnert</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Li_X/0/1/0/all/0/1">X. Li</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Litvinov_O/0/1/0/all/0/1">O. Litvinov</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Lock_J/0/1/0/all/0/1">J. Lock</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Longo_G/0/1/0/all/0/1">G. Longo</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Majewski_P/0/1/0/all/0/1">P. Majewski</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+McDonald_A/0/1/0/all/0/1">A. B. McDonald</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+McElroy_T/0/1/0/all/0/1">T. McElroy</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+McGinn_T/0/1/0/all/0/1">T. McGinn</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+McLaughlin_J/0/1/0/all/0/1">J. B. McLaughlin</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Mehdiyev_R/0/1/0/all/0/1">R. Mehdiyev</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Mielnichuk_C/0/1/0/all/0/1">C. Mielnichuk</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Monroe_J/0/1/0/all/0/1">J. Monroe</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Nadeau_P/0/1/0/all/0/1">P. Nadeau</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Nantais_C/0/1/0/all/0/1">C. Nantais</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Ng_C/0/1/0/all/0/1">C. Ng</a>, <a href="http://arxiv.org/find/nucl-ex/1/au:+Noble_A/0/1/0/all/0/1">A. J. Noble</a>, et al. (29 additional authors not shown)

The DEAP-3600 experiment is searching for WIMP dark matter with a 3.3 tonne
single phase liquid argon (LAr) target, located 2.1 km underground at SNOLAB.
The experimental signature of dark matter interactions is keV-scale $^{40}$Ar
nuclear recoils (NR) producing 128 nm LAr scintillation photons observed by
PMTs. The largest backgrounds in DEAP-3600 are electronic recoils (ER) induced
by $beta$ and $gamma$-rays originating from internal and external
radioactivity in the detector material. A background model of the ER
interactions in DEAP-3600 was developed and is described in this work. The
model is based on several components which are expected from radioisotopes in
the LAr, from ex-situ material assay measurements, and from dedicated
independent in-situ analyses. This prior information is used in a Bayesian fit
of the ER components to a 247.2 d dataset to model the radioactivity in the
surrounding detector materials. While excellent discrimination between ERs and
NRs is reached with pulse shape discrimination, utilizing the large difference
between fast and slow components of LAr scintillation light, detailed knowledge
of the ER background and activity of detector components, sets valuable
constraints on other key types of backgrounds in the detector: neutrons and
alphas. In addition, the activity of $^{42}$Ar in LAr in DEAP-3600 is
determined by measuring the daughter decay of $^{42}$K. This cosmogenically
activated trace isotope is a relevant background at higher energies for other
rare event searches using atmospheric argon e.g. DarkSide-20k, GERDA or LEGEND.
The specific activity of $^{42}$Ar in the atmosphere is found to be $40.4 pm
5.9$ $mu$Bq/kg of argon.

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