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 TAUP 2019 for the DEAP Collaboration Toyama

3279 kg

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 210 Pb (RPT was fabricator of the SNO Acrylic Vessel) Assay of production acrylic < 2.2x10 -19 g/g 210 Pb • (Corina Nantais M.Sc. Thesis 2014, <0.2 bkg events/3 years) Monomer cast at RPT Asia, 2010 Thermoformed Panel at RPT Colorado Mark Boulay

DEAP Acrylic Vessel Fabrication Reynolds Polymer (Colorado) 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) University of Alberta

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

Mark Boulay

Light guides on AV Reflectors on light guides PMT and inner detector installation Oct 2014 7

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

m 2 in 9 m in-situ situ

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 cm 2 at 100 GeV/c 2 (90% CL) Design sensitivity at this WIMP mass is 1.6 x 10 -46 cm 2 PRD 100 022004 2019. → 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/keV ee (NR bkg in WIMP search ROI) Dominant source: shadowed a decays from 210 Po 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

Remember: the neck Flow guides Muon Veto (300t H 2 O) 3.3t LAr 14 Neck Veto Mark Boulay

Shadowed a decays from liquid argon in neck region lead to low-energy backgrounds 210 Po 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 Mark Boulay

More advanced Other searches and measurements with DEAP 42 Ar/ 42 K specific activity (submitted) • Less advanced 39 Ar specific activity • 39 Ar spectroscopy, measurement of the Q-value and decay parameters • 36 Ar 0 νECEC search • Measurement of 8 B solar neutrinos in argon • Evaluation of short-lived cosmogenic muon isotope production in LAr • Modeling α scintillation in LAr • Other DM scenarios: • AUGUST 2019 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) 17

Argon and xenon complementarity 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)

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 39 Ar 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) 222 Rn backgrounds (0.2 m Bq/kg) and NR backgrounds in ROI ( 0.07 ± 0.03 events/tonne.year/keV ee ) Plan to increase sensitivity with (a) multivariate analysis and (b) physical reduction of 210 Po 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 39 Ar 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 m Bq/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 = “ D ark matter E xperiment using A rgon P ulse- shape discrimination” *need to be careful about pileup and efficiency, etc.

Global Argon Dark Matter Collaboration (Sep 2017) Over 350 researchers from o DarkSide o DEAP multi-hundred-tonne DS-20K o ArDM @SNOLAB @LNGS o MiniCLEAN collaborating on future program: o Completion of current science and R&D programs by each collaboration o Joint collaboration on DS-20k at LNGS (100 to 200 tonne-year exposure) see talks by De Cecco (DM1), Savarese (NT3) this conference o Extraction of ~50 tonnes of low 39 Ar underground argon for DS-20k, then ~400 tonnes for future detector (storage facility at SNOLAB: ARGUS). See talk by Bonivento (NT3) this conference o Joint collaboration on future multi-hundred-tonne LAr detector to reach neutrino floor at SNOLAB (~202X+) technology TBD Mark Boulay

THANK YOU! Mark Boulay