Direct Dark Matter searches with DEAP. Simon JM Peeters

Transcription

1 Direct Dark Matter searches with DEAP Simon JM Peeters

2 Outline The case for Dark Matter Direct Dark Matter detection Current experiments DEAP-3600 Overview & future experiment (DEAP/CLEAN) 2

3 The case for Dark Matter 3

4 Rotation of galaxies Vera Rubin Fritz Zwicky 4

5 Much more evidence 5

6 ΛCDM Atoms: free H & He: 4% stars: 0.5% neutrinos: 0.3% Credits: NASA/WMAP WMAP 9 year results heavy elements: 0.03% Dark matter 24% of the universe! 6

7 Dark Matter properties 150 kpc optically dark density around 0.3 GeV/cm3 15 kpc dark matter particle mass is not well bound (1 GeV -100 TeV) interactions: very weak, practically collision-less 7

8 Dark Matter properties 150 kpc Open questions: Mass? Interaction cross-section? Spin? Other quantum numbers? 15 kpc One particle species or more? Long-lived or stable? 8

9 The quest to elucidate the nature of dark matter and dark energy is at the heart of particle physics the study of the basic constituents of nature... Sciene #1 question: what is the Universe made of an area of world leading science opportunity signifcant UK leadership UK involvement is essential An answer to the question [what is dark matter] would mark a major breakthrough in understanding the universe and would open an entirely new feld of research on its own. 9

10 The hunt for DM Annihilation in the cosmos Production in colliders FERMI, Pamela, ATTIC Direct detection by scattering in terrestrial detectors HESS, VERITAS, Magic IceCube 10

11 Direct Dark Matter Detection 11

12 Direct detection Signal: χ χ v/c 8 x 10 Er -4 v/c 0.3 Backgrounds: 12

13 WIMP scattering Spin Independent: χ scatters coherently off of the entire nucleus A: σ A2 D. Z. Freedman, PRD 9, 1389 (1974) Spin Dependent: only unpaired nucleons contribute to scattering amplitude: σ J(J+1) 13

14 Measurement Recoil Nucleus Kinetic Energy χ χ N 14

15 Direct Detection Sc int illa ti χ kevr vs kevee on Heat Ion iza t ion A 15

16 Rate change and directionality 16

17 Different techniques 17

18 Current detectors and results 18

19 Xenon-100 results 19

20 Xenon-100 XENON100: a large, homogeneous, scalable detector Particle interaction in the active volume produces prompt scintillation light (S1) and ionization electrons Electrons drift to interface (E= 0.5 kv/cm) where they are extracted and amplifed in the gas. Detected as proportional scintillation light (S2) (S2/S1)WIMP << S2/S1)Gamma 3-D position sensitive detector with particle ID 20

21 DAMA/LIBRA 25 crystals in 5x5 grid (9.7 kg each) = 243 kg Two light guides + two PMTs on each crystal PMTs work in coincidence at the single photon electronic threshold There are correlations... Definite signal: but is it Dark Matter? 21

22 CoGeNT P-type point contact 440 g detector Low 0.4 kevee threshold Soudan Mine, Minnesota 22

23 CRESST Use scintillating CaWO4 crystals Detect both phonon signal and scintillation Multiple targets per detector CRESST is not claiming to see WIMPS 23

24 Low mass region Studied in detail: when interpreting the observed excesses as DM, they are in tension with each other. 24

25 DEAP

26 DEAP collaboration University of Alberta B. Beltran, R. Chouinard, P. Davis, A. Hallin, P. Gorel, D. Grant, S. Liu, T. McElroy, C. Ng, J. Soukup, R. Soluk, J. Tang, A. Vinagreiro Carleton University C. Brown, K. Graham, C. Ouellet, Laurentian University B.T. Cleveland, T. Pollman Queen s University M.G. Boulay, B. Broerman, B. Cai, D. Bearse, M. Chen, K. Dering, R. Gagnon P. Harvey, C. Hearns, M. Kuźniak, A.B. McDonald,. C. Nantais, T. Noble, P. Pasuthip, W. Rau, P. Skensved, T. Sonley, L. Veloce Royal Holloway University of London A. Butcher, E. Grace, R. Guenette, J. Monroe, N. Slim, J. Walding, M. Widorski Rutherford Appleton Laboratory P. Majewski, R. Shah SNOLAB I. Lawson, F. Duncan, R. Ford, C.J. Jillings, O. Li, E.Vázquez-Jáuregui University of Sussex S. Churchwell, G. Booker, S. J. M. Peeters TRIUMF P.-A. Amaudruz, D. Bishop, S. Chan, C. Lim, A. Muir, C. Ohlmann, K. Olchanski, F. Retiere, V. Strickland 26

27 Scintillation light in LAr 27

28 Pulse Shape Discrimination (PSD) Single-phase LAr detectors possible because of rejection power from timing, potential for kt scale detectors. LAr scintillates with a prompt and slow component: McKinsey & Coakley, Astropart. Phys. 22, 355 (2005) Boulay and Hime, Astropart. Phys. 25, 179 (2006) Lippincott et al., Phys.Rev.C 78: (2008) identify and reject electronic backgrounds Important for LAr: 39Ar beta (1 Bq/kg) Achieved e- leakage <3x10-8 in photo-electron window (Jillings, CAP '11) Expected <1x10-10 for DEAP-3600 for the same PE window 28

29 Depleted Argon 39Ar beta decays with 565 kev endpoint, at ~1 Bq/kg with half-life 269 years 39Ar production supported by cosmogenic activation, underground Ar has less! low-background Ar sources reduce 39Ar by a factor of 50 at least (counting-only analysis) A. Wright, arxiv:

30 Ar discrimination 39 30

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32 Single phase concept Liquid Argon dark matter wavelength shift target (cold! 87 K) (TPB) to >400 nm LAr scintillates at 128 nm read out with PMTs, digitize at 250 MHz, maximize PE/keVee with 4π coverage 32

33 DEAP/CLEAN family 33

34 SNOLAB deepest and cleanest large-space international facility in the 6000 mwe 34

35 SNOLAB 35

36 DEAP-3600 design Neck Steel shell Acrylic vessel (AV) with TPB scintillator layer Acrylic light guide High density polyethelyne fller material 255 Hamamatsu R5912 HQE PMTs 3600 kg LAr Detector in 8 m water shield, instrumented with veto PMTs 36

37 DEAP-3600 specifcations Parameters Light yield Value 8 pe per kevee Nuclear quenching factor Analysis threshold kevee (60 kevr) Total Argon mass (radius) 3600 kg (85 cm) Fiducial mass (radius) 1000 kg (60 cm) Position resolution at threshold (cons, design spec) Position resolution at threshold (ML ftter) Background specifications 10 cm < 6.5 cm Target < 1.4 nbq/kg Radon in Argon Surfaces α s (tolerance using cons. pos. res.) Surfaces α s (tolerance using ML ftter pos. res.) < 0.2 μbq/m2 < 100 μbq/m2 Neutrons (all sources, in fducial volume) < 2 pbq/kg βγ events, dominated by 39Ar (after PSD) < 2 pbq/kg Total backgrounds < 0.6 events in 3 tonne-years ArXiv:

38 Background reduction in prototype Demonstrated a detailed understanding of surface alpha backgrounds: an issue for all dark matter detectors By-product: Surface roughness interpretation of CRESST-II result : arxiv: Accepted for publication in Astropart. Phys. DEAP-1: 7 kg LAr ArXiv:

39 Cavity status at SNOLAB Cavity and platform are ready Water shield has been installed Services are ready 26 Simon Feb JM 2013 Peeters, DEAP, DESY 12/11/

40 Cryocooler and LN2 system Delivery and acceptance at SNOLAB (April 2012) 40

41 Thermoforming vessel Reynolds polymer, Colorado R&D fnished 2012 (thickness/radius of curvature radius larger than ever attempted before) 41

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43 Light guide and PMTs PMT assembly: components have been prototyped, purchased (PMTs, testing is underway), or quotes are being received. Lightguides: Radiopure acrylic bonded and shipped to TRIUMF Jan 2012 for machining 26 Simon Feb JM 2013 Peeters, DEAP, DESY 12/11/

44 Acrylic resurfacer Being commissioned at Queen s University on test blocks Resurfacer will be emanated to demonstrate radon load before shipping to SNOLAB 26 Simon Feb JM 2013 Peeters, DEAP, DESY 12/11/

45 TPB deposition Deposition source has been successfully demonstrated at Queen s University in evaporation test stand. 26 Simon Feb JM 2013 Peeters, DEAP, DESY 12/11/

46 Steel shell Welded underground Electropolished on the inside (Rn emanation) Steel shell is being constructed in the cube hall at SNOLAB 46

47 Calibration programme Characterise the response in energy, radius and fprompt Calibration using internal and external gamma sources (RAL) Co (1.17 and 1.33 MeV γ) ; 22Na (e+,1.274 kev γ);137cs (0.662 kev γ), 83Krm (9+32 kev γ) 60 Neutron calibration (RHUL) Deployable, pulsed D-D generator Optical calibration (Sussex) LED/fbre optical injection system LED ball calibration pre and post TPB deposition 266 nm laser injection via the neck to excite TPB 47

48 Understanding TPB (DM, neutrino, 0νββ relevance) Test TPB response in detail: intensity timing wavelength (modified set-up with spectrometer) as function angle TPB deposition thickness excitation wavelength 26 Simon Feb JM 2013 Peeters, DEAP, DESY 12/11/

49 Project overview Detector assembly and commissioning Detector assembly and commissioning Resurfacing Resurfacing Apply TPB Apply Start TPBof Dark Matter run Dec Jun Dec Jun Overview of the timeline for DEAP Simon Feb JM 2013 Peeters, DEAP, DESY 12/11/

50 Overview & future detectors 50

51 Xenon-100 results 51

52 The context 52

53 There is a limit.. impossible to shield a detector from coherent neutrino scattering: Φ(solar B8) = 5.86 x 106 cm-2 s-1 ν ν J. Monroe, P. Fisher, PRD76: (2007) Z N N nuclear recoil fnal state 1 event/ton-year =~ cm2 limit in zero-background paradigm... unless you measure the direction! 53

54 Two phase vs single phase Xe: demonstrated and no 39Ar high light yield and selfshielding of liquid noble target background discrimination from prompt scintillation timing... no electric felds = straightforward scalability 1) no pile-up from ms-scale electron drift in E 2) no recombination in E (high photons/kevee) but no charge background discrimination either! 54

55 Ultimately & Strong backing from Canada UK ownership of calibration WP 55

56 Background reduction and in-situ measurement plus scalibility DEAP/CLEAN family 56

57 CLEAN 7M 26 Simon Feb JM 2013 Peeters, DEAP, DESY 12/11/ M 57

58 Initial studies Where MiniCLEAN and DEAP-3600 need a surface activity near 1 Bq/m2/day CLEAN limits are based on 180 Bq/m2/hour (6 months of assembly in mine air) Challenges: Calibration DAQ 26 Simon Feb JM 2013 Peeters, DEAP, DESY 12/11/

59 Summary Science case for Direct Dark Matter detection is very strong and it is a vibrant and exciting feld of research DEAP-3600 is a very interesting technique promising to set a world limit and a vital step to the ultimate size (non-directional) detector 59

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