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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,

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Presentation on theme: "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,"— Presentation transcript:

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, 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

2 Evidence for Dark Matter measure velocity of gas/stars vs radius from galactic centre v 2 c = 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 Mihos NGC 2403 HST Abell % of matter is dark matter!

3 Direct Detection of Dark Matter predict at the earth: dark matter energy density 0.3 GeV/cm 3 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 keV  use LAr with PSD DM signal or improve limit on scattering cross-section (expect 10’s of events/year)  40 Ar  Cold Dark Matter  WIMPS (can also be LSP!)

4 Detection in LAr ionizing radiation forms dimers in LAr dimers produced in singlet(I 1 ) or triplet(I 3 ) 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

5  -like neutron-like

6 ~1 kg LAr viewed by single 2” PMT CsI counter used for tag calibration with tagged  ’s, n’s 22 Na: back-to-back 511 keV  ’s AmBe: n and 4.4 MeV  demonstrate pulse shape discrimination determine  suppression level (expect O(10 8 ) from MC simulation) measure I 1 /I 3 for  ’s and neutrons PMT LAr CsI tag Vacuum chamber windows source DEAP0 at LANL (Boulay and Hime) SetupGoals Digitized Pulse Total Charge

7 Deap0 Calibration 22 Na 511 keV  AmBe neutron 22 Na 511 keV  determine charge/single PE know peak for 22 Na is 511 keV  ~0.1 PE/keV  (sets sensitivity) PromptPE = integral in 250 ns TotalPE = integral to 10  s FPrompt=PromptPE/TotalPE expect ~0.3 for  ~0.8 for n

8 22 Na AmBe determine fraction of 22 Na above 0.7  for PE suppression O(10 5 ) consistent with background limits neutrons in region above 0.7 uncorrected  and neutron I 1 /I 3 use background data to determine real and accidental coincidence rate Preliminary Results

9 DEAP1  ~10 kg of liquid argon view with 2 - 5” PMT’s  use clean materials and shielding in construction  calibrate detector response at Queen’s  move 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

10 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 and Gas/liquid lines

11 DEAP1 Constructed! first LAr fill 2 weeks ago response looks good! begin calibrating next week

12 Backgrounds TypeSourcesRateSuppressionMethod U/Th/K 39 Ar 10 6 events/year clean materials PSD (10 8 ) clean Ar?  ’srecoilsionizing R&D in progress position recon. clean materials PSD neutronthermal fast( ,n) muon induced 4000 /m 2 /day <0.27 /m 2 /day shielding clean materials SNOLAB depth

13 DM Sensitivity with LAr with 1-year exposure LAr with 10 keV (electron) threshold DEAP1

14 Summary 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!

15 210 Po on surface Decay in bulk detector tagged by  -particle energy Decay from surface releases untagged recoiling nucleus Cryostat wall LAr   Fig 6: Alpha emitters deposited on the detector surface are a potentially dangerous background.

16 Radon Contamination 210 Po on surface Decay in bulk detector tagged by  -particle energy Decay from surface releases untagged recoiling nucleus Cryostat wall LAr   minimize exposure clean/etch surfaces reconstruction suppression

17

18 Dewar Schematic liquefy purified Argon gas and maintain at 85 o K vacuum chamber argon line liquid nitrogen at ~30 PSI getter

19 CDMS (Cryogenic Dark Matter Search) ZIP detector 250 g Ge Image 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 in deposited charge versus phonon energy between  ‘s and nuclear recoils (Currently instrumented 5 kg mass)

20 Backgrounds CDMS Collab Meeting 15 Oct 2005

21 cm 2 (100 kg LAr) Direct detection prediction from SUSY NMSSM (Next-to-MSSM) Prediction from talk by David Cerdeno at SUSY 2005 (JHEP 12 (2004) 048) cm 2 (10 kg LAr) maybe within our reach!

22 SNOLAB Excavation Status DEAP Collab Mtg 10 May 2006

23 Evidence for Dark Matter angular power spectrum of CMB sensitive to baryonic, DM, DE clustering of galaxies (LSS) sensitive to amount of DM Virgo Consortium Add breakdown of matter content here

24 For almost as long as WIMPs have been around (if they DO exist!)… U, Th chains are present in all materials with 10 9, y lifetimes ~10 4 decays/kg/year for ppt (1 in ) impurities Removing backgrounds to WIMP particle interactions is the task of DM searchers

25 CDMS (Cryogenic Dark Matter Search) ZIP detector 250 g Ge Image 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 in deposited charge versus phonon energy between  ‘s and nuclear recoils (Currently instrumented 5 kg mass)

26 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

27 Background rejection with LAr (simulation) From simulation, rejection > keV (>>!) 10 8 simulated e-’s 100 simulated WIMPs

28 Triplet lifetime check

29 Photomultiplier tube (PMT) backgrounds in DEAP-1 For reference, 250 events/year for the ET9390 PMTs

30 Optimizing optics for DEAP -1 Y=R [1/S-1]  lg  pmt (1-  )Y 0 Model incorporating reflective losses and absorption: Y = yield [photons/keV] R = surface reflectivity S = surface PMT coverage  lg = light guiding efficiency  pmt = PMT efficiency  = absorption Y 0 = photon production yield  lg = 0.8 epmt = 0.25  = 0 Y 0 = 40 photons/keV Need real model to map inputs to yield, O(10%) (Kati N.)

31 Dark 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!

32 Evidence for Dark Matter angular power spectrum of CMB sensitive to baryons, DM, DE 85% of matter is dark matter! neutrinos ~few % of matter WMAP Three Year Results

33 Summary using SNOLAB facility and based on the experience and success of SNO, there is a unique opportunity for 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 physics for low-energy solar neutrinos and experiment is built! DEAP can rapidly evolve from concept to leading edge dark matter experiment – simple, inexpensive, scalable!

34 Backgrounds 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!


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