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,

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

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!

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!)

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

-like

neutron-like

• ~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

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

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

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

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

DEAP1 Constructed!DEAP1 Constructed!

first LAr fill 2 weeks agoresponse looks good!begin calibrating next week

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

DM Sensitivity with LAr with 1-year DM Sensitivity with LAr with 1-year exposureexposure

LAr with 10 keV (electron) threshold

DEAP1

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!

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

Dewar SchematicDewar Schematic

liquefy purified Argon gasand maintain at 85o K

vacuum chamber

argon line

liquid nitrogen at ~30 PSI

getter

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)

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

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!

SNOLAB Excavation StatusSNOLAB Excavation Status

DEAP Collab Mtg 10 May 2006

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

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

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)

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

Background rejection with LAr (simulation)

From simulation,rejection > 108

@ 10 keV(>>!)

108 simulated e-’s

100 simulatedWIMPs

Triplet lifetime check

Photomultiplier tube (PMT) backgrounds in DEAP-1

For reference, 250 events/year for the ET9390 PMTs

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.)

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!

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

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!

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!