Direct Searches for Dark Matter and the CDMS Experiment

Transcription

1 Direct Searches for Dark Matter and the CDMS Experiment P. Di Stefano, Queen's P. Di Stefano Queen's University Dark matter Basics of direct detection CDMS and others

2 A 62 Year Old Problem Fritz Zwicky and the Coma galaxy cluster Helv. Phys. Acta, 6, N 2, p 110, 1933 ρgravitation > 400 ρluminous Dark Matter? st èmes

3 Gravitational Lensing Efect of general relativity: NASA NASA P. Di Stefano, Queen's Sensitive to total mass of lens: Visible Dark

4 Dark Matter in Galaxy Clusters Mluminous Coma, optical Mgas / 10 Mtotal / 100 Coma, X-ray P. Di Stefano, Queen's , lensing

5 Matter in the Universe Most matter appears only through gravitational efects Dark Matter at all Scales Big Bang Nucleosynthesis: most of the dark matter is non-baryonic Possible explanations? Gravity wrong??? Massive Compact Halo Objects (MACHOs)? Microlensing? Galaxies (rotation curves) Clusters Large-scale structure Neutrinos? Structure Formation? New Particles: Weakly Interacting Massive Particles (WIMPs)?...? Cosmic Microwave Background P. Di Stefano, Queen's

6 The Standard Model of Particle Physics Fermions and bosons P. Di Stefano, Queen's Several particles predicted before they were discovered Strong evidence for all particles except Higgs boson (needed to explain masses): Tevatron, Large Hadron Collider? Many parameters (>18)? Gravity?

7 7 Solution to Dark Matter: SUSY WIMPs? Supersymmetry (SUSY): So far undetected extension of standard model that may solve some of its riddles Fermions Bosons LSP (χ): Lightest SUSY Particle Probably neutralino Stable if R-parity conserved mχ GeV-TeV ( mproton) Relevant relic abundance: Broken at usual energies Pagels & Primack PRL Ω χ 0.1 Coupling to matter: Spin independent: σ α A2 µ 2 σp Spin dependent: σ = C J(J+1) µ 2 σp LEP, Tevatron m > 46 GeV (J. Ellis et al., hep-ph/ ) st èmes

8 Complementarity of searches Annihilation Indirect Detection χ χ q q Production Colliders Scattering Direct Detection (Adapted from A Morselli) P. Di Stefano, Queen's Direct detection: May fnd evidence for WIMPs Would not provide details Colliders (LHC): missing energy May be fastest method Stability of particles? Indirect detection: annihilation products Need to deconvolve astrophysics from particle physics Would give information on both Methods sensitive to diferent regions of parameter space

9 Direct Detection of WIMPs Seek elastic scattering of WIMPs themselves in detector (Drukier and Stodolsky Phys. Rev. D 30(11) , Goodman & Witten Phys. Rev. D31(12) ) Counting experiments: build it and they will come? Theoretical ingredients: WIMP local astrophysical distribution (speeds v rms 250 km/s, density 0.3 GeV/cm3...) Some uncertainties (graininess: Zemp et al 2008; non-maxwellian: Stif & Widrow 2003) Cross-section (SI, SD) Kinematics (elastic scattering) Nuclear form-factor (loss of coherence) Recoil spectrum: P. Di Stefano, Queen's v dr n0 2 F E v 2 de v 0 max min f v dv v

10 Spectra: Efect of WIMP Mass P. Di Stefano, Queen's Exponential-ish shape Few counts: <1/kg/month The needle The lighter the WIMP, the faster the fall Detector threshold efect

11 11 WIMPs vs Materials Slopes: kinematics form factor Integral: cross-section: A4 (target mass)-1: A-1 st èmes

12 12 Ideal Experiments (No Background) Same exposure (MT), threshold: sensitivities similar No background: sensitivity MT Real experiment: bckgd!. No rejection: sensitivity limited by background Partial bckgd rejection: sensitivity MT Total rejection: sensitivity MT

13 Escaping the Haystack in Mines and Tunnels: Going Underground to Reduce Background Homestake/DUSEL 7500 mwe (?) JinPing YangYang ~6000 mwe ~2000 mwe Cosmic muon Log(µ fux) (/m2/s) 106 /m2/d fux reduced Lewin & Smith, /m2/d Smith & Lewin, Phys. Rep km Depth (m water equivalent) 13

14 SNOLAB, Sudbury ON One of the deepest and cleanest labs P. Di Stefano, Queen's DEAP PICASSO (Dark (DM) CDMS? Matter) (DM) 00 1 ~ SNO+ (neutrinos) m Also: HALO (neutrinos), PUPS (seismology)...

15 SNOLAB, Sudbury ON One of the deepest and cleanest labs The mine P. Di Stefano, Queen's After shower/carwash, the labs: 5000 m2 total Class 2000 cleanroom Local areas cleaner

16 DUSEL Delayed? 17 Dec 2010: Science Feb 2011: President's FYI 2012 budget: P. Di Stefano, Queen's

17 SNOLAB: the competition USA (DUSEL) Delayed sine die Europe (LSM) ULISSE extension being discussed at 4500 mwe Funding decision expected summer 2011 Not ready before 2016? China (JinPing) New player in a difcult feld... should not be underestimated Golden window of scientifc opportunity for SNOLAB P. Di Stefano, Queen's

18 Human radioactivity Typical human Main contributions: radioactivity: 8 kbq 40 K: T1/2 = 1,3*109 y 11% γ: E = 1,5 MeV 14 C: T1/2 = 5730 y Untypical isotopic composition 8 kbq/80 kg = 100 disintegrations /s/kg P. Di Stefano, Queen's 89% β-: E < 1,3 MeV 100% β-: E < 156 kev

19 19 Radioactivity of Materials All must be tested for radioactivity Shield experiment: Pb for γ PE for neutrons Archaeological Pb: U was removed during founding 238 U gives 210Pb Found in shipwrecks... Even shielding radioactive Pb: 47 kev γ, 22 y 210 L'Hour et al, Rev. Arch. Ouest

20 Low-Background Wine Testing 20 (P. Hubert et al. Nucl. Phys. News Internat. 13, 1, 2003) End of atmospheric Cs content of wine bottle testing Activity measured on low background Ge counter (Bq/l) 137 Chernobyl Up to 1 Bq/l Age of Bordeaux wine linked to 137Cs contents Non-destructive test!

21 21 Some Direct Detection Experiments Ionization in semi-conductors (ionization) Ahlen et al Caldwell et al 1994 Heidelberg-Moscow 200? GERDA Majorana COGENT Scintillators (photons) 1996 DAMA, UKDMC LIBRA

22 (adapted from S Leman, MIT) 250 kg Gran Sasso 400 g PPC Soudan Selvi, LVD, Muons at Gran Sasso P. Di Stefano, Queen's Many things have annual modulation mu-induced fuorescence (Nygren 2011)? Interesting NaI development: South Pole

23 23 Some Direct Detection Experiments Ionization in semi-conductors (ionization) Ahlen et al Caldwell et al 1994 Heidelberg-Moscow Scintillators (photons) 1996 DAMA, UKDMC 200? GERDA Majorana COGENT LIBRA Cryogenic calorimeters (phonons + scintillation/ionization) 2000CDMS, CRESST, EDELWEISS CDMS II EDELWEISS II CRESST II +CUORE

24 Basic Principle of Cryogenic Calorimetry A particle deposits energy E in absorber Absorber: Heat capacity C Temperature T Thermal link Thermal resistance R (th. conductance G) If no thermal link, T steps up by E/C Thermal link allows relaxation back to T0: -t/rc T(t)-T0 = E/C e T Heat sink, T0 t

25 Transition-Edge Sensors (TES) 5x5 mm2 x 200 nm tungsten (W) thin film Exploit sharp normalsuperconducting transition R Τ= E/C

26 P. Di Stefano, Queen's Structured W TES (Al2O3 substrate) Al W Au Al 1 mm Courtesy F. Petricca, MPP

27 27 Typical 262 g Sapphire Performances (Phonon only, CRESST expt)

28 Removing the Haystack: Ionization-Phonon Detectors (T. Shutt et al. PRL , L. Bergé et al. NPB ) Heat sink (T 10 mk) Thermometer R(T) Phonons - e U Absorber (ex: Ge, 100g) Holes Recoil (Erec 10 kev) Electrodes Incoming particle (m 10 GeV, Ekin 50 kev) Phonon signal: T/T 0.1% over ms Charge signal: 1000 pairs over µs γ, β particles ionize more than WIMPs, neutrons Event by event background rejection 28

29 CDMS: the Cryogenic Dark Matter Search Caltech Z. Ahmed, J. Filippini, S. Golwala, D. Moore Southern Methodist University D.A. Bauer, J. Hall, F. DeJongh, D. Holmgren, L. Hsu, R.L. Schmitt, J. Yoo Syracuse University Fermilab MIT E. Figueroa-Feliciano, S. Hertel, K. McCarthy, S.W. Leman, P. Wikus NIST K. Irwin Queen's University P. Di Stefano, J. Fox, S. Liu, C. Martinez, P. Nadeau, W. Rau Santa Clara University B.A. Young Stanford University P.L. Brink, B. Cabrera, M. Pyle, M. Razeti, S. Yellin SLAC/KIPAC M. Asai, A. Borgland, D. Brandt, W. Craddock, E. do Couto e Silva, G. Godfrey, J. Hasi, M. Kelsey, C. Kenney, P.C. Kim, R. Partridge, R. Resch, D. Wright. J. Cooley R.W. Schnee, M. Kos and M. Kiveni University of California, Berkeley M. Daal, N. Mirabolfathi, B. Sadoulet, D. Seitz, B. Serfass, K. Sundqvist University of California, Santa Barbara D. O. Caldwell University of Colorado at Denver M. E. Huber, B. Hines University of Florida T. Saab, J. Hoskins, D. Balakishiyeva University of Minnesota H. Chagani, P. Cushman, S. Fallows, M. Fritts, S. Hofer V. Mandic, A. Reisetter, O. Kamaev, A. Villano, J. Zhang University of Texas A&M R. Mahapatra, M. Platt, J. Sander

30 Ionization-Phonon Particle Identifcation 30 Adapted from J Hall, FNAL CDMS ZIP detectors: Ge 230 g each γ induced events (main background, here 133Ba source) Excellent separation down to 10 kev neutron-induced evts (signal region, here 252Cf source)

31 31 Cryogenic Dark Matter Search (CDMS) Science, 2010 Ionization-phonon detectors Phonon channel timing zsensitivity improved rejection of surface events Soudan 19 Ge detectors, 230 g each Exposure: MT = 612 kg.d 2 events in signal region after cuts 0.9 expected from known backgrounds (25% chance of stat fuctuation)

32 Dealing with Surface Events Surface background may be misidentifed because of poor charge collection Ionization Yield Identify surface events via Signal Recoil Energy (kev) Region P. Di Stefano, Queen's phonon channel ionization channel

33 33 Some Direct Detection Experiments Ionization in semi-conductors (ionization) Ahlen et al Caldwell et al 1994 Heidelberg-Moscow Scintillators (photons) 1996 DAMA, UKDMC LIBRA Cryogenic calorimeters (phonons + scintillation/ionization) 2000CDMS, CRESST, EDELWEISS CDMS II EDELWEISS II CRESST II +CUORE Noble liquids (scintillation + ionization) ZEPLIN 200? GERDA Majorana COGENT XENON, XMASS WArP, ArDM, DEAP Other techniques PICASSO PICASSO,MIMAC DRIFT, COUPP

34 34 Noble Liquids: Discrimination & Mass? Element A Ar Xe 39,9 131,3 Boiling point 87 (K) Density 1,4 (g/cm3) Discrimination S1/S2, S1 PSD Radioactive 39Ar isotopes DM projects & WArP, experiments ArDM, DEAP 165 Electro-luminescence 2,9 WIMP, neutron, γ... S1/S2 Scintillation ZEPLIN, XENON, LUX Figs. L Grandi, INFN Pavia (WArP)

35 35 WIMP Limits (SI, 90% CL) EDELWEISS CDMS XENON No background subtraction Now entering SUSY predictions Race is on between small cryogenic detectors and large noble liquid ones

36 Low Mass WIMPs? (accepted PRL 2011) CDMS XENON conservative P. Di Stefano, Queen's DAMA SI WIMP? CoGeNT WIMP? XENON CDMS-SUF DAMA SD WIMP? CDMS XENON Difcult to reconcile - DAMA-CoGeNT WIMP - CDMS-XENON

37 Towards a joint CDMS-EDELWEISS analysis Recent results from EDELWEISS (arxiv How to combine data? ) PRELIMINARY 10x400 g ionisation-phonon detectors In 384 kg.d, 5 evts at E > 20 kev Sensitivity close to CDMS for heavy WIMPs P. Di Stefano, Queen's

38 38 Next Generation Cryogenic Experiments CDMS, EDELWEISS, CRESST running 10's of kg background discrimination Surface events and neutron background? CDMS II 4 kg Ge ~ 2 yrs operation Soudan 15 kg Ge ~ 2 yrs operation Snolab 100 kg Ge ~ 3 yrs operation DUSEL/GEODM Phase III (100's of kg) SNO EURECA: EDELWEISS, CRESST, CERN... Goal: σ=10-10 pb in next few years Ton scale expt: σ=10-12 pb Likely to be a transatlantic endeavor Specifc challenge: mass production of 1000 detectors and readout

39 A la recherche de la matière perdue Astrophysics and particle physics still faced with dual challenge of dark matter and supersymmetry Cryogenic detectors with excellent background rejection are well placed to confrm or invalidate SUSY WIMPs Healthy, complementary, competition from heavier noble liquid detectors Great opportunity for major discovery (at SNOLAB?) in the next few years P. Di Stefano, Queen's