1. July 21-23, 2008OCPA Workshop on Underground Science 1 Dark Matter Search at SNOLAB with DEAP-1 and DEAP/CLEAN-3600 Bei Cai （蔡蓓） For the DEAP/CLEAN Collaboration Queen’s University, Canada

2. 2 WIMP-nucleon cross section 3600 kg LAr CDMS-II: ~120 kg-days (Ge) XENON-10: ~300 kg-days (Xe) DEAP/CLEAN: 1,000,000 kg-days (Ar) CDMS, arXiv:0802.3530

3. The DEAP/CLEAN Collaboration Boston University D. Gastler, E. Kearns Carleton University K. Graham Los Alamos National Laboratory C. Alexander, S. Elliott, G. Garvey, V. Gehman, V. Guiseppe, A. Hime, W. Louis, S. McKenney, G. Mills, K. Rielage, L. Rodriguez, L. Stonehill, R. Van de Water, H. White, J. Wouters MIT Joe Formaggio NIST, Boulder K. Coakley Queen’s University M. Boulay, B. Cai, M. Chen, P. Harvey, J. Lidgard, A. McDonald, P. Pasuthip, T. Pollman, P. Skensved TRIUMF F. Retiere Laurentian University/ SNOLAB B. Cleveland, F. Duncan, C. Jillings, I. Lawson SNOLAB I. Lawson, K. McFarlane University of Alberta A. Hallin, R. Hakobyan, K. Olsen, J. Soukup University of New Mexico D. Loomba University of North Carolina R. Henning University of South Dakota D. Mei University of Texas, Austin J. Klein, S. Seibert Yale University L. Kastens, W. Lippincott, D. McKinsey, K. Ni, J. Nikkel 15 institutes in Canada and USA, ~ 50 researchers

4. 4 The DEAP/CLEAN experiments DEAP-1: 7 kg LAr prototype experiment Run at Queen’s for demonstration of PSD Installed underground at SNOLAB 2007 for continued PSD and background studies, DM search MicroCLEAN 2 kg prototype experiment at Yale University MiniCLEAN: 360 kg experiment targeting DM with LAr and prototyping neon for particle astrophysics Primary emphasis of US collaborators in short term DEAP/CLEAN-3600: 3600 kg experiment targeting DM with LAr Primary emphasis of Canadian collaborators in short term

5. 5 Argon is a good WIMP detection target Excellent PSD between electron recoils and nuclear recoils Good scintillator (40 photons/keV) Inexpensive and easy to purify Single-phase detector, easy to scale up with “standard” assumptions about the WIMP distribution and for a 100 GeV WIMP Rate ~ A 2 F (coherent) Loss of coherence for large nuclei

6. 6 χ 40 Ar χ Direct WIMP detection with liquid argon Energy transfer in liquid argon leads to formation of excited dimers Dimer molecules are in either singlet or triplet states, and the lifetimes are well-separated: – ~ 6 ns for singlet state (prompt) – ~ 1.59 µs for triplet state (delayed)

7. 7 Fraction of dimers in singlet or triplet states depends on the incident particle type Pulse-shape discrimination A. Hitachi et al., Phys. Rev. B 27 (9) (1983) 5279

8. 8 ET 9390B PMT 5” 8” long acrylic guide 11” x 6” (8” CF) tee Acrylic vacuum chamber Glass windows Poly PMT supports Inner surface 97% diffuse reflector, covered with TPB wavelength shifter Neck connects to vacuum and gas/liquid lines 7 kg LAr DEAP-1 detector

9. 9 SAES getter Ar liquefying chamber

10. 10 F prompt : the discriminator Yellow: Prompt light region Blue: Late light region Backgrounds (  ’s) Signal (nuclear recoil)

11. 11 AmBe (neutron) calibration

12. 12  Neutron backgrounds  Muon suppression at SNOLAB  Clean materials and shielding  Surface contamination  Clean detector surface (resurfacer device)  vertex reconstruction for fiducial volume  β,γ backgrounds  Pulse-shape discrimination Backgrounds Ar-39 is the largest source of background For DEAP-1, the expected βrate from Ar-39 decay is ~6×10 6 for 7 kg-years in 20-40 keVee

13. 13 22 Na e-e- e+e+ 511 keV γ 1.274 MeV γ 511 keV γ Argon Dark box Annulus NaI 22 Na Tagged Na-22 setup at Queen’s

14. 14 Single PE calibration Gain: ~10 7 Energy calibration using Na-22 Light yield: ~2.8 PE/keV

15. 15 Detector stability

16. 16 ROI Tagged Na-22 data 1.53x10 7 events in energy ROI: (120, 240) PEs, (40, 80) keVee

17. 17 Probability of leakage

18. 18 Pulse-shape background discrimination

19. 19 DEAP-1 at SNOLAB

20. 20 Queen’s SNOLAB (“radon-dirty” chamber) Livetime ~6 hrsLivetime ~10 hrs x10 reduction residual backgrounds consistent with radon daughter contamination, now reduced with glove box surface removal

21. 21 Radon-222 decay rates 10 decays/m 2 of air (surface labs) 100 decays/m 2 of air (at SNOLAB) Decay in bulk detector tagged by  -particle energy LAr   Cryostat Wall 210 Po on surface Decay from surface releases untagged recoiling nucleus Daughters from radon decay can be implanted into surfaces  210-polonium alpha energy = 5.4 MeV E N =103 keV r (sub-micron implantation)

22. 22

23. 23 veto PMTs H 2 O shield (7.8 m) 266 8” PMTs 170 cm ID acrylic vessel (3600 kg LAr) DEAP/CLEAN-3600 detector design

24. 24 Acrylic vessel resurfacer for radon removal

25. 25 SNOLAB cube hall SNOLAB Cube Hall SNO DEAP-1 DEAP/CLEAN-3600

26. 26 MiniCLEAN DEAP/CLEAN-3600

27. 27 Summary and outlook DEAP-1 has successfully demonstrated a PSD level of 6x10 -8 Will continue running at SNOLAB for a goal of PSD 1x10 -9, and for dark matter search DEAP/CLEAN-3600 is being designed and has a sensitivity of 10 -46 cm 2 Begin shield tank and platform installation later this year Plan to start data taking for 3600 kg in 2010