Dark Matter Search with DEAP-3600 at SNOLAB: Status and Plans Mark - - PowerPoint PPT Presentation

Dark Matter Search with DEAP-3600 at SNOLAB: Status and Plans

Mark Boulay Carleton University for the DEAP Collaboration TAUP 2019 Toyama

3279 kg

Mark Boulay

Fabrication and Assay of DEAP Acrylic

• Fabrication from pure MMA monomer at RPTAsia (Thailand), strict control of radon exposure

for all steps, to < 10-20 g/g 210Pb (RPT was fabricator of the SNO Acrylic Vessel)

• Assay of production acrylic < 2.2x10-19 g/g 210Pb

(Corina Nantais M.Sc. Thesis 2014, <0.2 bkg events/3 years)

Thermoformed Panel at RPT Colorado Monomer cast at RPT Asia, 2010

DEAP Acrylic Vessel Fabrication

Reynolds Polymer (Colorado) University of Alberta Underground at SNOLAB

Panels thermoformed and bonded into sphere At RPT Colorado (2011) Machined at University of Alberta (2011, 2012) Shipped to SNOLAB, neck and light guides bonded (2012-2014)

Mark Boulay

Bonding light guides to the DEAP AV, underground at SNOLAB

Light guides bonded then annealed in radon-reduced air oven >5 meter attenuation length in light guide acrylic! DEAP AV in “The Rotator” at SNOLAB

Mark Boulay

Reflectors on light guides PMT and inner detector installation Oct 2014 Light guides on AV

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Dark Matter in Hollywood WIMP detector in “Scorpion TV series on CBS” 2018

An 18 foot tall sanding robot was deployed in the AV to remove inner surface layer of acrylic (and Rn progeny) “The Resurfacer”

2016 J. Phys.: Conf. Ser. 718 042025

9 m m2 in in-situ situ

Mark Boulay

Construction of DEAP-3600 was completed in 2016

Detector paper: 1712.01982, Astropart. Phys. 108 1 (2019)

Mark Boulay

Dark matter search results and sensitivity projections

DEAP-3600 latest published limit: 3.9 x 10-45 cm2 at 100 GeV/c2 (90% CL) PRD 100 022004 2019. Design sensitivity at this WIMP mass is 1.6 x 10-46 cm2 → Currently factor of ~14 away from xenon at high mass for “standard” assumptions What next?

Mark Boulay

Some comments (background table from PRD 100 022004 2019) Background rate is LOW! 𝟏. 𝟏𝟖 ± 𝟏. 𝟏𝟒 ev/t.y/keVee (NR bkg in WIMP search ROI) Dominant source: shadowed a decays from 210Po on neck flowguides Current published WIMP-search sensitivity from cut-and-count analysis; will increase sensitivity with multivariate analysis Also planning to re-configure detector to remove the source of these background events

Mark Boulay

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Remember: the neck

Muon Veto (300t H2O) 3.3t LAr Neck Veto Flow guides

Mark Boulay

Shadowed a decays from liquid argon in neck region lead to low-energy backgrounds

210Po

Mark Boulay

Two options to deal with neck events in hardware

• 1. Coat neck flowguides with a “slow” wavelength shifter to remove neck

events with PSD (development in progress) See related arxiv:1903.00257 (2019)

• 2. Reconfigure detector cooling to keep flowguide region warm

(no liquid on flowguides = no neck events) Planning to select and implement fix in 2020, then run to full design sensitivity (2021-2022) In parallel with improvements from using multivariate analysis

Other searches and measurements with DEAP

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• 42Ar/42K specific activity (submitted)
• 39Ar specific activity
• 39Ar spectroscopy, measurement of the Q-value and decay parameters
• 36Ar 0νECEC search
• Measurement of 8B solar neutrinos in argon
• Evaluation of short-lived cosmogenic muon isotope production in LAr
• Modeling α scintillation in LAr
• Other DM scenarios:
• Solar axion search at 5.5 MeV
• Axion-like Particle and Hidden Photon DM search
• Low threshold analysis and search for annual modulation
• Search for warm sterile neutrinos
• Boosted dark matter
• Multiply Interacting Massive Particles (MIMPs)
• Constraints on DM interactions based on effective field theory-derived

interaction terms and extragalactic halo contributions (driven by recent galactic survey analyses)

More advanced Less advanced

AUGUST 2019

arxiv.org/abs/1902.10256 In general, combination of argon+xenon is a powerful tool to constrain models that predict changes in cross sections or recoil spectra (ie. isospin violating DM, Self Interacting Dark Matter) Argon and xenon complementarity

DEAP-3600 Summary

Running since 2016, leading sensitivity for high-mass WIMPs with argon. Starting (for the first time, in 2019) to provide complementary info to xenon for models which predict relative change in cross-section or spectral shape Extremely powerful ER discrimination, works as expected but require lower 39Ar for larger detectors. ER backgrounds are essentially not a concern for argon DM detectors (although they limit the low energy threshold, so limit “background-free” sensitivity to high-mass WIMPs, > ~30 GeV) Demonstrated excellent position resolution using scintillation-only LAr Demonstrated extremely low neutron-induced backgrounds possible through passive shielding and ultrapure materials selection (ie, acrylic) Demonstrated extremely low (lowest) 222Rn backgrounds (0.2 mBq/kg) and NR backgrounds in ROI (0.07 ± 0.03 events/tonne.year/keVee ) Plan to increase sensitivity with (a) multivariate analysis and (b) physical reduction of 210Po events on neck flowguides (in progress…)

Additional comments

PSD can be used to control ER backgrounds toneutrino floor: 1/2 tonne-year exposure with DEAP @ 1 Bq/kg of 39Ar corresponds to 700 tonne-year exposure with low-radioactivity underground argon (x1400 reduction), so ER backgrounds, including eventually from n-electron elastic scattering, not a concern in argon* Radon backgrounds already low enough (0.2 mBq/kg in DEAP-3600) Surface backgrounds easier to handle in larger detectors, can more easily fiducialize, either with TPC (DS-20k) or with photon time-of-flight Aside: DEAP= “Dark matter Experiment using Argon Pulse-shape discrimination”

*need to be careful about pileup and efficiency, etc.

Mark Boulay

Global Argon Dark Matter Collaboration (Sep 2017)

Over 350 researchers from

• DarkSide
• DEAP
• ArDM
• MiniCLEAN

collaborating on future program:

• Completion of current science and R&D programs by each collaboration
• Joint collaboration on DS-20k at LNGS (100 to 200 tonne-year exposure)

see talks by De Cecco (DM1), Savarese (NT3) this conference

• Extraction of ~50 tonnes of low 39Ar underground argon for DS-20k, then

~400 tonnes for future detector (storage facility at SNOLAB: ARGUS). See talk by Bonivento (NT3) this conference

• Joint collaboration on future multi-hundred-tonne LAr detector to reach

neutrino floor at SNOLAB (~202X+) technology TBD DS-20K @LNGS multi-hundred-tonne @SNOLAB

Mark Boulay

THANK YOU!