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![Page 1: The DEAP Experiment The DEAP Experiment Dark Matter Experiment with Argon PSD Kevin Graham Queen’s University M. Boulay, M. Chen, K. Graham, A. Hallin,](https://reader036.fdocuments.net/reader036/viewer/2022062417/551c22cd5503469e4f8b5c30/html5/thumbnails/1.jpg)
The DEAP ExperimentThe DEAP Experiment Dark Matter Experiment with Argon PSD
Kevin GrahamKevin Graham
Queen’s University
M. Boulay, M. Chen, K. Graham, A. Hallin, J. Lidgard, R. Matthew,
A.B. McDonald, K. Nicolics, P. Skensved
Case Western Reserve University
M. Dragowsky
Los Alamos National Laboratory
Hime, D. Mei, K. Rielage, L. Stonehill, J. Wouters
SNOLAB
F. Duncan, I. Lawson
Yale University
D. McKinsey, J. Nikkel
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Evidence for Dark MatterEvidence for Dark Matter•measure velocity of gas/stars vs radius from galactic centre
v2c = G M(r) / r
•if light traces mass v should fall at large radii…but does not
•lensing measure lens mass from multiply imaged arcs•measure velocities of galaxies in cluster
MihosNGC 2403
HST A
bell
22
18
85% of matter is dark matter!
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Direct Detection of Dark MatterDirect Detection of Dark Matter
predict at the earth:• dark matter energy density 0.3 GeV/cm3
• Sun orbiting at 220 km/s• for a given mass and interaction cross-section estimate -n scattering rate /kg/year/keV
direct measurement:look for: elastic scattering of WIMPs in detector producing nuclear recoils low energy and falling 10-100 keVuse LAr with PSDDM signal or improve limit on scatteringcross-section (expect 10’s of events/year)
40Ar
40Ar
Cold Dark Matter WIMPS (can also be LSP!)
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Detection in LArDetection in LAr• ionizing radiation forms dimers in LAr• dimers produced in singlet(I1) or triplet(I3) state• singlet state decay time much shorter than triplet• intensity of singlet and triplet states depends on ionization density along track and hence particle type
ns
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-like
neutron-like
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• ~1 kg LAr viewed by single 2” PMT• CsI counter used for tag• calibration with tagged ’s, n’s 22Na: back-to-back 511 keV ’s AmBe: n and 4.4 MeV
• demonstrate pulse shape discrimination• determine suppression level (expect O(108) from MC simulation)• measure I1/I3 for ’s and neutrons
PMT LAr CsI tag
Vacuum chamber
windows source
DEAP0 at LANL (Boulay and Hime)
Setup Goals
Digitized Pulse
Total Charge
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Deap0 CalibrationDeap0 Calibration
22Na 511 keV
AmBe neutron 22Na 511 keV
•determine charge/single PE•know peak for 22Na is 511 keV ~0.1 PE/keV (sets sensitivity)
PromptPE = integral in 250 nsTotalPE = integral to 10 s
FPrompt=PromptPE/TotalPE
expect ~0.3 for ~0.8 for n
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22Na
AmBe
determine fractionof 22Na above 0.7 for 55-65 PE suppression O(105)consistent withbackground limits
neutrons in regionabove 0.7
uncorrected and neutron I1/I3
use background data to determine real and accidental coincidence rate
Preliminary Results
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DEAP1DEAP1
~10 kg of liquid argon view with 2 - 5” PMT’suse clean materials and shielding in constructioncalibrate detector response at Queen’smove to SNOLAB early in 2007
•measure suppression down to 10 keV threshold•position reconstruction in “z”•at SNOLAB understand background rates/types •can already be competitive within a few months exposure!
•prepare for 1 tonne experiment
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PMT 5”6” acrylic guide
11” x 6” Stainless steel tee
Acrylic vacuum chamber
Quartz windows
inner surface 97% diffuse reflector,covered with TPB wavelength shifter
Neck connects to vacuum andGas/liquid lines
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DEAP1 Constructed!DEAP1 Constructed!
first LAr fill 2 weeks agoresponse looks good!begin calibrating next week
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BackgroundsBackgrounds
TypeType SourcesSources RateRateSuppressionSuppression
MethodMethod
U/Th/KU/Th/K3939ArAr
106
events/year106
events/year
clean clean materialsmaterials
PSD (10PSD (1088))
clean Ar?clean Ar?
’srecoilsrecoils
ionizingionizing
R&D inR&D in
progressprogress
position position recon.recon.
clean clean materialsmaterials
PSDPSD
neutronthermalthermal
fast(fast(,n),n)
muon inducedmuon induced
4000 /m4000 /m22/day/day
4000 /m4000 /m22/day/day
<0.27 /m<0.27 /m22/day/day
shieldingshielding
clean clean materialsmaterials
SNOLAB depthSNOLAB depth
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DM Sensitivity with LAr with 1-year DM Sensitivity with LAr with 1-year exposureexposure
LAr with 10 keV (electron) threshold
DEAP1
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SummarySummary
• initial proof-of-principle PSD (complete)• calibration of DEAP1 at Queen’s (first fill so far)PE/keV, reconstruction, /n response at 10 keV• calibrate and understand backgrounds at depth • if bkg controlled competitive DM limits soon!
begin design of DEAP3 (1 tonne) experiment!
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Radon ContaminationRadon Contamination
210Po on surface
Decay in bulk detector tagged by -particle energy
Decay from surface releasesuntagged recoiling nucleus
Cryostatwall
LAr
•minimize exposure•clean/etch surfaces•reconstruction suppression
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Dewar SchematicDewar Schematic
liquefy purified Argon gasand maintain at 85o K
vacuum chamber
argon line
liquid nitrogen at ~30 PSI
getter
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CDMS (Cryogenic Dark Matter CDMS (Cryogenic Dark Matter Search)Search)
ZIP detector 250 g GeImage from cdms.berkeley.edu
Collection of small detectors simultaneously measure deposited energy in charge and phonon channels
~1 kg / “tower”Current best limit
rays
neutrons
Exploits difference indeposited charge versusphonon energy between ‘s and nuclear recoils
(Currently instrumented5 kg mass)
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BackgroundsBackgrounds
CDMS Collab Meeting 15 Oct 2005
FluxMuonsNeutrons (Thermal)Neutrons (Fast) Radon (Surface)Radon (UGLab) 3.3± 0.4 pCi/L
Rock (Norite)K 1.20%
1.2 ppm3.2ppm
OtherBats
<0.27/m²/day4144.9±49.8±105.3 n/m²/day~4000 n/m²/day0.15± 0.12 pCi/L
238U232Th
2x10-7/m2/day
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10-45 cm2 (100 kg LAr)
Direct detection prediction from SUSY
NMSSM (Next-to-MSSM)Prediction from talk byDavid Cerdeno at SUSY 2005(JHEP 12 (2004) 048)
10-44 cm2 (10 kg LAr)
maybe within our reach!
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SNOLAB Excavation StatusSNOLAB Excavation Status
DEAP Collab Mtg 10 May 2006
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Evidence for Dark MatterEvidence for Dark Matter
angular power spectrum of CMBsensitive to baryonic, DM, DE
clustering of galaxies (LSS)sensitive to amount of DM
Virgo Consortium
Add breakdown of matter content here
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For almost as long as WIMPs havebeen around (if they DO exist!)…
U, Th chains are present inall materials with 109, 1010 y lifetimes
~104decays/kg/year for ppt (1 in 10-12) impurities
Removing backgrounds to WIMP particleinteractions is the task of DM searchers
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CDMS (Cryogenic Dark Matter CDMS (Cryogenic Dark Matter Search)Search)
ZIP detector 250 g GeImage from cdms.berkeley.edu
Collection of small detectors simultaneously measure deposited energy in charge and phonon channels
~1 kg / “tower”Current best limit
rays
neutrons
Exploits difference indeposited charge versusphonon energy between ‘s and nuclear recoils
(Currently instrumented5 kg mass)
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XENON (proposed experiment)XENON (proposed experiment)
Figure from Elena Aprile Dark Matter 2004
Total Xe mass 1 tonne
Exploits difference in ionization signal (electrons)versus scintillation signal(photons) between ‘s and nuclear recoils
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Background rejection with LAr (simulation)
From simulation,rejection > 108
@ 10 keV(>>!)
108 simulated e-’s
100 simulatedWIMPs
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Triplet lifetime check
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Photomultiplier tube (PMT) backgrounds in DEAP-1
For reference, 250 events/year for the ET9390 PMTs
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Optimizing optics for DEAP-1
Y=R[1/S-1] lgpmt(1-)Y0
Model incorporating reflective losses and absorption:
Y = yield [photons/keV]R = surface reflectivityS = surface PMT coveragelg = light guiding efficiencypmt = PMT efficiency = absorptionY0 = photon production yield
lg = 0.8
epmt = 0.25 = 0Y0 = 40 photons/keV
Need real model to map inputs to yield,O(10%) (Kati N.)
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Dark Matter CandidatesDark Matter Candidates
Baryonic Dark Matter - MACHOs - Brown Dwarfs
Hot Dark Matter - neutrinos
Non-Standard Gravity - MOND
Cold Dark Matter - Axions - WIMPs
- R-parity conserving supersymmetric models predict stable LSP (typically neutralino ) - can have ‘right’ properties for cold dark matter!
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Evidence for Dark MatterEvidence for Dark Matter
angular power spectrum of CMBsensitive to baryons, DM, DE
85% of matter is dark matter!neutrinos ~few % of matter
WMAP Three Year Results
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SummarySummary
using SNOLAB facility and based on the experienceand success of SNO, there is a unique opportunityfor Canadians to lead experimental research in
- direct search for dark matter - low-energy solar neutrinos - neutrinoless double beta decay SNO+ will have access to most interesting physicsfor low-energy solar neutrinos and experiment is built!
DEAP can rapidly evolve from concept to leading edgedark matter experiment – simple, inexpensive, scalable!
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BackgroundsBackgrounds
• expect DM small signal /keV/tonne/day
• background suppression crucial
• non-nuclear recoil events PSD
• nuclear recoil events (shielding, reconstruction)
• clean clean clean clean clean!