1. TeV Particle Astrophysics II - Madison – August 30, 2006 Elena Aprile, Columbia University Future of Dark Matter Direct Detection (with Cryogenic Noble Liquids) Elena Aprile Physics Department and Columbia Astrophysics Laboratory Columbia University http://xenon.astro.columbia.edu/

2. TeV Particle Astrophysics II - Madison – August 30, 2006 Elena Aprile, Columbia University Direct Detection Methods/Experiments DAMA/LIBRA EDELWEISS CDMS XENON, XMASS-II, ZEPLIN2, ZEPLIN3, WARP, ArDM CRESST ZEPLIN1 XMASS Mini-CLEAN Double Phase (Xe, Ar)

3. TeV Particle Astrophysics II - Madison – August 30, 2006 Elena Aprile, Columbia University Goal: Cover Supersymmetry World-best limit today CDMS II 2007 SuperCDMS Phase C 1000 kg of Ge SuperCDMS 25kg 25 kg of Ge 2011 SuperCDMS Phase B 150 kg of Ge ZEPLIN I EDELWEISS ZEPLIN 2 XENON 10 DAMA 10 -45 cm 2 10 -47 cm 2 10 -46 cm 2

4. TeV Particle Astrophysics II - Madison – August 30, 2006 Elena Aprile, Columbia University Cryogenic Noble Liquids Suitable materials for detection of ionizing tracks: u Dense, homogeneous, target and also detector u Do not attach electrons u High electron mobility (except neon in some conditions) u Commercially easy to obtain and to purify u Inert, not flammable, very good dielectrics Element Liquid Density (  /cm 3 ) Energy loss dE/dx (MeV/cm) Radiation length X 0 (cm) Collision length (cm) Boiling point @ 1 bar (K) Electron mobility (cm 2 /Vs) Neon1.21.4248027.1high&low Argon1.42.1148087.3500 Krypton2.43.04.9291201200 Xenon3.03.82.8341652200 $ $$ $$$ Cost From C. Rubbia

5. TeV Particle Astrophysics II - Madison – August 30, 2006 Elena Aprile, Columbia University LXe & LAr for Dark Matter Direct Detection Liquid Xenon  Large A (~ 131): good SI case (  ~ A 2 ) but low threshold a must  Presence of 129 Xe (26.4%) and 131 Xe (21.2.4%) good for SD u No long-lived radioisotopes. Kr85 fraction to ppt level proven u Excellent stopping power for compact, self-shielding geometry u ‘Easy’ cryogenics at -100 C u Efficient scintillator ( 80% of NaI) with fast time response u Background Discrimination Methods: Charge and Light ratio plus 3D event localization Liquid Argon u A=40 good for higher mass WIMPs u No odd isotopes for SD u 39 Ar at ~1 Bq/kg require rejection > 10 7 u Not so “Easy” Cryogenics at – 186 C but easier to purify u Larger volumes required to compensate low Z and density  larger size cryostat and shielding (cost) but raw Ar is cheap u Background Discrimination Methods: Charge and Light ratio plus 3D event localization plus Light PSD Integrated Rates Above Threshold Differential Rates

6. TeV Particle Astrophysics II - Madison – August 30, 2006 Elena Aprile, Columbia University Dual Phase TPCs with Simultaneous Charge and Light Readout: XENON – ZEPLIN –WARP – ArDM  XMASS (Scintillating LXe Calorimeter - 800 kg  Solar Neutrino/Dark Matter  Kamioka See Y.Koshio talk at http://cryodet.lngs.infn.it/agenda/agenda.html  XMASSII (Double Phase LXe-15 kg)  Dark Matter  Kamioka See S.Suzuki talk at http://cryodet.lngs.infn.it/agenda/agenda.htm  Mini-CLEAN/DEAP ( Scintillating LNe/LAr Calorimeter - 100Kg)  Solar Neutrino/Dark Matter  SNOLAB/Homestake? See D.McKinsey talk at http://www.physics.ucla.edu/hep/dm06/talks.htmlhttp://www.physics.ucla.edu/hep/dm06/talks.html Single Phase LXe or LAr Scintillating Detectors: recent talks

7. TeV Particle Astrophysics II - Madison – August 30, 2006 Elena Aprile, Columbia University Dual Phase TPC Principle of Operation WIMP or Neutron nuclear recoil electron recoil Gamma or Electron

8. TeV Particle Astrophysics II - Madison – August 30, 2006 Elena Aprile, Columbia University The XENON Experiment: Overview 1 ton target distributed in TPC modules each with ~ 100kg active Xe, viewed by low activity VUV PMTs directly coupled to liquid/gas. Event-by-event discrimination of nuclear recoils from electron recoils (>99%) down to 16 keVr from a) simultaneous detection of scintillation (S1) and ionization (via proportional scintillation S2) and b) 3D event localization with millimeter resolution. Phase 1 (XENON10) : TPC prototype with 15 kg active target. Operating underground (Gran Sasso) with passive gamma/neutron shield. ~50kg-day exposure as of today! 1 st physics results soon. Funded by NSF and DOE. Phase 2 (XENON100) : design studies started, assuming present location and shield. Final design to be determined by XENON10 performance. Goal is to have XENON100 taking physics data by 2008. Phase 3 (XENON1T): to be defined by results from XENON Phase 2 and other experiments worldwide

9. TeV Particle Astrophysics II - Madison – August 30, 2006 Elena Aprile, Columbia University XENON: Dual-Phase XeTPC with 3D Event Imaging Background Discrimination simultaneous detection of scintillation (S1) and ionization (via proportional scintillation S2) signals down to 16 keV nuclear recoil energy 3D event localization with millimeter spatial resolution XENON Phased Program Modular design: 1 ton in ten 100 kg modules XENON10 Phase: TPC module with 15 kg active target moved underground (Gran Sasso Laboratory) in March 06. Shield construction completed July 06. Dark Matter Search now ongoing. Funded by NSF and DOE XENON100 Phase: design/construction in FY07/08 (2M$ construction). Commission and start underground operation in 2008.

10. TeV Particle Astrophysics II - Madison – August 30, 2006 Elena Aprile, Columbia University XENON Dark Matter Goals SUSY Theory Models Dark Matter Data Plotter http://dmtools.brown.edu http://dmtools.brown.edu CDMS II goal SUSY Theory Models XENON10 (2006-2007): 10 kg target ~2 events/10kg/month XENON100 (2008-2010): 100 kg target ~2 events/100kg/month XENON-1T (>2010): 1 ton target ~1 event/1 tonne/month

11. TeV Particle Astrophysics II - Madison – August 30, 2006 Elena Aprile, Columbia University Columbia University Elena Aprile (PI), Karl-Ludwig Giboni, Maria Elena Monzani,, Guillaume Plante*, and Masaki Yamashita Brown University Richard Gaitskell, Simon Fiorucci, Peter Sorensen*, Luiz DeViveiros* Case Western Reserve University Tom Shut t, Eric Dahl*, John Kwong* and Alexander Bolozdynya Lawrence Livermore National Laboratory Adam Bernstein, Norm Madden and Celeste Winant Rice University Uwe Oberlack, Roman Gomez* and Peter Shagin Yale University Daniel McKinsey, Richard Hasty, Angel Manzur*, Kaixuan Ni RWTH Aachen University, Germany Laura Baudis, Jesse Angle*, Joerg Orboeck, Aaron Manalaysay* Laboratori Nazionali del Gran Sasso, Italy Francesco Arneodo, Alfredo Ferella* University of Coimbra, Portugal Jose Matias Lopes, Luis Coelho*, Luis Fernandes, Joaquim Santos The XENON10 Collaboration

12. TeV Particle Astrophysics II - Madison – August 30, 2006 Elena Aprile, Columbia University 9 young PostDoc scientists- 11 graduate students Many of them at LNGS

13. TeV Particle Astrophysics II - Madison – August 30, 2006 Elena Aprile, Columbia University Ionization and Scintillation in Noble Liquids I/S (electron) >> I/S (non relativistic particle) Alpha scintillation electron scintillation Electron charge Alpha charge Electric Field (kV/cm) L/L0 or Q/Q0 (%) Recombination Excitation (Xe*) Ionization (Xe +, e) Xe 2 * ( 1  ,  3   )  2Xe+h (175 nm) FastSlow

14. TeV Particle Astrophysics II - Madison – August 30, 2006 Elena Aprile, Columbia University Recent Highlights from XENON R&D Scintillation Efficiency of Nuclear Recoils in LXe Aprile et al., Phys. Rev. D 72 (2005) 072006 Ionization Yield of Nuclear Recoils in LXe Aprile et al., accepted in PRL (2006)

15. TeV Particle Astrophysics II - Madison – August 30, 2006 Elena Aprile, Columbia University Case ELASTIC Neutron Recoils INELASTIC 129Xe 40 keV  + NR INELASTIC 131Xe 80 keV  + NR 137Cs  source Upper edge -saturation in S2 AmBe n-source Neutron ELASTIC Recoil 5 keVee energy threshold = 10 keV nuclear recoil Columbia+Brown Nuclear and Electron Recoils Discrimination

16. TeV Particle Astrophysics II - Madison – August 30, 2006 Elena Aprile, Columbia University  1 “ square PMTs: Hamamatsu R8520-06-Al  Metal Channel, compact (3.5cm long); QE>20% Background Rejection by S2/S1 and 3D Event Localization Neutron Elastic Recoil 40 keV Inelastic ( 129 Xe) + NR 80 keV Inelastic ( 131 Xe) 110 keV inelastic ( 19 F) + NR Neutron Elastic Recoil 40 keV Inelastic ( 129 Xe) + NR 80 keV Inelastic ( 131 Xe) + NR Edge Events reduced by 5 mm radial cut: XENON3 TPC exposed to 2.5 MeV neutrons

17. TeV Particle Astrophysics II - Madison – August 30, 2006 Elena Aprile, Columbia University Pulse tube cryocooler 15 kg LXe XENON10 Vacuum Cryostat Re-condenser  TPC active area ~ 20 cm diameter; LXe drift gap= 15 cm  22 kg (15 kg active) Xe mass  1kV/cm drift field - Custom designed HV feedthrough.  SS vessel and vacuum cryostat.  89 PMTs (R8520-06-AL): 48 in GXe and 41 in LXe  Light response (S1) : 2 pe/keV at 1 kV/cm  Pulse Tube Refrigerator for stable operation at –95C.

18. TeV Particle Astrophysics II - Madison – August 30, 2006 Elena Aprile, Columbia University XENON10: TPC Details Bottom PMT Array, PTFE Vessel Top PMT Array PMT Base (LLNL) LN Cooling Loop Level Meters (Yale) Grids, Tilmeters (Case) HV- FT

19. TeV Particle Astrophysics II - Madison – August 30, 2006 Elena Aprile, Columbia University XENON10 underground at the Gran Sasso Laboratory March 2006: XENON10 shipped from Nevis Labs to LNGS and commissioning starts underground. Detector is tested/calibrated in temporary location while passive shield is designed/built. Move detector in shield in July 2006. XENON10 filled with low Kr-Xe; DM Search starts August 2006

20. TeV Particle Astrophysics II - Madison – August 30, 2006 Elena Aprile, Columbia University XENON10 Shield 3500 mm 2410 mm 200 mm 40 ton Pb + 3.5 ton Poly: ( 210 Pb 30 Bq/kg) inner Pb & ( 210 Pb 500 Bq/kg) Outer Pb Inner Cavity for Detector: 90 cm x 90 cm x1.1 m (H)

21. TeV Particle Astrophysics II - Madison – August 30, 2006 Elena Aprile, Columbia University : XENON10 : 3D Event Localization Events are localized in X,Y,Z: 1)Z position determined by drift time, time b/w S1 and S2 2)X&Y positions reconstructed from S2 detected by top 48 PMTs (in gas), based on a simulated map. S2S1 3D event localization is in good agreement with MC (data from a Cs-137 calibration run). Min-Chisq position reconstruction for an edge event.

22. TeV Particle Astrophysics II - Madison – August 30, 2006 Elena Aprile, Columbia University XENON10 – MC Estimated Background Rate Original XENON10 Goal Electron Recoils <0.14 /keVee/kg/day (assumes 99.5% electron recoil rejection) Application of 1 cm surface cut 15 kg -> 10 kg LXe Radius (10 cm) - Depth (15 cm) Event Rates (log(/keV/kg/day)) In XENON10 Stainless Steel Cryostat & PMTs (background in 5-25 keVee) [Dominant BGs] u Stainless: MC using value of 100 mBq/kg 60Co u PMTs - 17.2/<3.5/12.7/<3.9 mBq/kg (U/Th/K/Co) - 89 Low activity 1” Hamamatsu tubes – Note: more PMTs are being screened to validate the activity inferred from a sample of four Radius (cm) Depth (cm)

23. TeV Particle Astrophysics II - Madison – August 30, 2006 Elena Aprile, Columbia University WIMP-search data : 3D Event distribution ( < 100 keVee) Z -distribution R- distribution X-Y distribution High Z (= 54) allows us to effectively reject background by fiducial volume cuts  self-shielding capability.

24. TeV Particle Astrophysics II - Madison – August 30, 2006 Elena Aprile, Columbia University > Factor 100 !! After fiducial volume cuts which rejects most electron recoils  10kg mass. As of today we have 50kg-day exposure Note low threshold <16 keVr!! Background Reduction by Self-Shielding

25. TeV Particle Astrophysics II - Madison – August 30, 2006 Elena Aprile, Columbia University Background Reduction by Self-Shielding Top Bottom > Factor 100 !! After fiducial volume cuts Which rejects most electron recoils. Note low threshold!

26. TeV Particle Astrophysics II - Madison – August 30, 2006 Elena Aprile, Columbia University XENON1 ～ 20cm ～ 60cm R&D: 2002-5 DM search:2006-7 DM Search:2008-9 XENON100 ～ 10cm XENON10 XENON3 XENON Scale-Up 2005-9

27. TeV Particle Astrophysics II - Madison – August 30, 2006 Elena Aprile, Columbia University ZEPLIN II Design Principle e-e- (S2) (S1) PM T LXe gas liquid γ n- r e-e- PM T PTFE ZEPLIN2 Rochester, SMU, TAMU, UCLA, RAL, Imperial College, Sheffield, ITEP, Coimbra 45kg Xenon (Fiducial 32kg)

28. TeV Particle Astrophysics II - Madison – August 30, 2006 Elena Aprile, Columbia University  ZEPLIN3 (Double Phase LXe- 6kg)  Dark Matter  Boulby See T. Sumner talk at http://cryodet.lngs.infn.it/agenda/agenda.html

29. TeV Particle Astrophysics II - Madison – August 30, 2006 Elena Aprile, Columbia University WARP - WIMP Dark Matter Search with LAr Pavia, Napoli, LNGS, Princeton, Krakow High sensitive mass (140 kg scalable to 1 Ton) Detector threshold  20 keV Active shielding (8000 kg Liquid Argon and 400 3” PMTs) Gamma shield (Pb) Neutron shield (Polyethylene) Low activity materials inner detector active veto neutron and  shield Under construction at Gran Sasso underground Laboratories See talk by A. Cocco at Neutrino06

30. TeV Particle Astrophysics II - Madison – August 30, 2006 Elena Aprile, Columbia University The 2.3 litre prototype at LNGS PMTs: 7  2” (designed by EMI to work at 87 K) 7.5 cm depth (40  s max drift time with 1kV/cm) stable Argon purity (<1 ppb O 2 equiv.) Passive shield (10 cm Pb + 60 cm Polyethylene) Trigger threshold of about 5 keV (6 Hz rate) April 2004: Start of underground test-runs April 2006: 2.8  10 7 events collected in the last physics run PMTs Cathode Grids Race Tracks Liquid Argon Gas Argon Wavelength Shifter Reflector

31. TeV Particle Astrophysics II - Madison – August 30, 2006 Elena Aprile, Columbia University Results of WIMP search 90% C.L. upper limit No recoil-like events are observed above 42 keV ion in a total fiducial exposure of 96.5 kg x day (2.8 x 10 7 trigger) The evaluated 90% C.L. upper limit for spin-independent interaction, in the standard WIMP scenario, is plotted. Energy resolution due to statistical fluctuations and to a non uniform light collection has been taken into account The dominant systematic effect is due to uncertainties on scintillation yield. An error of 15% on Y Ar corresponds to a variation of 20% @ M W =100 GeV /c 2 and of 30% @ M W =50 GeV/c 2

32. TeV Particle Astrophysics II - Madison – August 30, 2006 Elena Aprile, Columbia University The ArDM Project ETH,Zurich, Granada,CIEMAT,Soltan Institut,Sheffield Field shaping + immersed HV multiplier WIMP GAr LAr E-field Charge extraction from liquid argon to gaseous argon, amplification and readout with Large Electron Multiplier (LEM) Light readout Cylindrical volume, drift length ≈ 120 cm 850 kg target Drift field ≈ 1 to 5 kV/cm Charge LEM readout: Single electron gain ≈ 10 3 to 10 4 Global light readout collection efficiency ≈ 5% Single photon detection Assumed baseline parameters: Reflecting mirrors detection principle See Talk by L. Kaufmann at this conference

33. TeV Particle Astrophysics II - Madison – August 30, 2006 Elena Aprile, Columbia University Prototype layout Two-stage LEM for electron multiplication and readout Greinacher chain: supplies the right voltages to the field shaper rings and the cathode up to 500 kV Field shapers are needed to provide a homogeneous electric field, but are thin enough to permit the scintillation light to be reflected from the container walls Transparent cathode ~85 PMTs below the cathode to detect the scintillation light

34. TeV Particle Astrophysics II - Madison – August 30, 2006 Elena Aprile, Columbia University Summary More than 30 years after Zwicky discovery, the nature of dark matter remains a mystery. Almost 1/3 of the density of the Universe is in a new form of matter. Standard Model of particle physics gives us a good view of our physics world but only …5% of it! How can we not seek to find out about the remaining 95% of the Universe composition? Particle physics theory beyond Standard Model (SUSY) provides ideal candidates as DM particles Strong experimental effort worldwide to look for presence of these new particles both in direct and indirect searches plus accelerator. Expect important results in the next 10 years. Direct WIMP detection - a very active field! Best sensitivity: CDMS II:  = 1.6 x 10 -43 cm 2 at M W = 60 GeV Large (>1ton) detectors needed for discovery (  = 10 -46 cm 2 ). LXe and LAr very promising LHC: discovery of SUSY its primary goal,…but need direct detection to confirm that the particle is the Dark Matter WIMP. Direct searches highly complementary to the LHC. In one sentence: … There has never been a better time to exploit the power of a noble liquid TPC for a major discovery in physics!