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Future of Dark Matter Direct Detection (with Cryogenic Noble Liquids)

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/. Direct Detection Methods/Experiments. XENON, XMASS-II, ZEPLIN2, ZEPLIN3, WARP, ArDM.

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Future of Dark Matter Direct Detection (with Cryogenic Noble Liquids)

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  1. 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. Direct Detection Methods/Experiments XENON, XMASS-II, ZEPLIN2, ZEPLIN3, WARP, ArDM Double Phase (Xe, Ar) DAMA/LIBRA ZEPLIN1 XMASS Mini-CLEAN EDELWEISS CDMS CRESST

  3. ZEPLIN I Goal: Cover Supersymmetry EDELWEISS DAMA World-best limit today ZEPLIN 2 CDMS II 2007 XENON 10 SuperCDMS 25kg 25 kg of Ge 2011 SuperCDMS Phase B 150 kg of Ge 10-45 cm2 SuperCDMS Phase C 1000 kg of Ge 10-46cm2 10-47cm2

  4. Cryogenic Noble Liquids Cost • Suitable materials for detection of ionizing tracks: • Dense, homogeneous, target and also detector • Do not attach electrons • High electron mobility (except neon in some conditions) • Commercially easy to obtain and to purify • Inert, not flammable, very good dielectrics $ $$ $$$ From C. Rubbia

  5. LXe & LAr for Dark Matter Direct Detection Liquid Xenon • Large A (~ 131): good SI case (s~ A2 ) but low threshold a must • Presence of 129Xe (26.4%) and 131Xe (21.2.4%) good for SD • No long-lived radioisotopes. Kr85 fraction to ppt level proven • Excellent stopping power for compact, self-shielding geometry • ‘Easy’ cryogenics at -100 C • Efficient scintillator ( 80% of NaI) with fast time response • Background Discrimination Methods: Charge and Light ratio plus 3D event localization Liquid Argon • A=40 good for higher mass WIMPs • No odd isotopes for SD • 39Ar at ~1 Bq/kg require rejection > 107 • Not so “Easy” Cryogenics at – 186 C but easier to purify • Larger volumes required to compensate low Z and density larger size cryostat and shielding (cost) but raw Ar is cheap • Background Discrimination Methods: Charge and Light ratio plus 3D event localization plus Light PSD Integrated Rates Above Threshold Differential Rates

  6. Dual Phase TPCs with Simultaneous Charge and Light Readout:XENON – ZEPLIN –WARP – ArDM Single Phase LXe or LAr Scintillating Detectors: recent talks • 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.html

  7. Dual Phase TPC Principle of Operation WIMP or Neutron nuclear recoil Gamma or Electron electron recoil

  8. 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 keVrfrom 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! 1st 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. XENON Dark Matter Goals CDMS II goal Dark Matter Data Plotterhttp://dmtools.brown.edu • 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 SUSY TheoryModels SUSY TheoryModels

  10. The XENON10 Collaboration 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 Shutt, 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

  11. Ionization and Scintillation in Noble Liquids I/S (electron) >> I/S (non relativistic particle) Ionization (Xe+, e) Excitation (Xe*) Alpha scintillation Electron charge L/L0 or Q/Q0 (%) electron scintillation Recombination Alpha charge Xe2* ( 1Su ,3Su )  2Xe+h (175 nm) Electric Field (kV/cm) Fast Slow

  12. Recent Highlights from XENON R&D Scintillation Efficiency of Nuclear Recoils in LXe Ionization Yield of Nuclear Recoils in LXe Aprile et al., accepted in PRL (2006) Aprile et al., Phys. Rev. D 72 (2005) 072006

  13. Columbia+Brown ELASTIC Neutron Recoils INELASTIC 131Xe 80 keV  + NR Upper edge -saturation in S2 INELASTIC 129Xe 40 keV  + NR Neutron ELASTIC Recoil AmBe n-source 137Cs  source 5 keVee energy threshold = 10 keV nuclear recoil Case Nuclear and Electron Recoils Discrimination

  14. Background Rejection by S2/S1 and 3D Event Localization 80 keV Inelastic (131Xe) 110 keV inelastic (19F) + NR 80 keV Inelastic (131Xe) + NR 40 keV Inelastic (129Xe) + NR 40 keV Inelastic (129Xe) + NR Neutron Elastic Recoil Neutron Elastic Recoil Edge Events reduced by 5 mm radial cut: XENON3 TPC exposed to 2.5 MeV neutrons • 1 “ square PMTs: Hamamatsu R8520-06-Al • Metal Channel, compact (3.5cm long); QE>20%

  15. XENON10 • 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. Pulse tube cryocooler Re-condenser 15 kg LXe Vacuum Cryostat

  16. XENON10: TPC Details Grids , Tilmeters (Case) LN Cooling Loop PMT Base (LLNL) Top PMT Array Bottom PMT Array, PTFE Vessel HV- FT Level Meters (Yale)

  17. 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

  18. XENON10 Shield 40 ton Pb + 3.5 ton Poly: (210Pb 30 Bq/kg) inner Pb & (210Pb 500 Bq/kg) Outer Pb Inner Cavity for Detector: 90 cm x 90 cm x1.1 m (H) 2410 mm 3500 mm 200 mm

  19. XENON10 – MC Estimated Background Rate Stainless Steel Cryostat & PMTs (background in 5-25 keVee) [Dominant BGs] • Stainless: MC using value of 100 mBq/kg 60Co • 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 (10 cm) - Depth (15 cm) Event Rates (log(/keV/kg/day)) In XENON10 Depth (cm) Depth (cm) Original XENON10 GoalElectron Recoils <0.14 /keVee/kg/day(assumes 99.5% electron recoil rejection) Application of 1 cm surface cut15 kg -> 10 kg LXe Radius (cm) Radius (cm)

  20. WIMP-search data: 3D Event distribution ( < 100 keVee) Z -distribution X-Y distribution R- distribution High Z (= 54) allows us to effectively reject background by fiducial volume cuts self-shielding capability.

  21. Background Reduction by Self-Shielding > 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!!

  22. Background Reduction by Self-Shielding Top > Factor 100 !! Bottom After fiducial volume cuts Which rejects most electron recoils. Note low threshold!

  23. XENON10 XENON100 XENON1 XENON3 ～10cm ～20cm ～60cm R&D: 2002-5 DM search:2006-7 DM Search:2008-9 XENON Scale-Up 2005-9

  24. PMT PMT PMT gas liquid e- (S2) e- LXe n-r γ (S1) PTFE ZEPLIN2 Rochester, SMU, TAMU, UCLA, RAL, Imperial College, Sheffield, ITEP, Coimbra ZEPLIN II Design Principle 45kg Xenon (Fiducial 32kg)

  25. ZEPLIN3 (Double Phase LXe- 6kg)Dark MatterBoulby See T. Sumner talk at http://cryodet.lngs.infn.it/agenda/agenda.html

  26. WARP - WIMP Dark Matter Search with LAr Pavia, Napoli, LNGS, Princeton, Krakow Under construction at Gran Sasso underground Laboratories See talk by A. Cocco at Neutrino06 •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 neutron and  shield active veto

  27. 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 O2 equiv.) •Passive shield (10 cm Pb + 60 cm Polyethylene) •Trigger threshold of about 5 keV (6 Hz rate) PMTs Gas Argon Grids Liquid Argon Race Tracks April 2004: Start of underground test-runs April 2006: 2.8  107 events collected in the last physics run Wavelength Shifter Reflector Cathode

  28. Results of WIMP search90% C.L. upper limit No recoil-like events are observed above 42 keVion in a total fiducial exposure of 96.5 kg x day(2.8 x 107 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 YAr corresponds to a variation of 20% @ MW=100 GeV /c2 and of 30% @ MW=50 GeV/c2

  29. The ArDM ProjectETH,Zurich, Granada,CIEMAT,Soltan Institut,Sheffield detection principle Reflecting mirrors Charge extraction from liquid argon to gaseous argon, amplification and readout with Large Electron Multiplier (LEM) GAr LAr E-field WIMP Field shaping + immersed HV multiplier Light readout Assumed baseline parameters: • Cylindrical volume, drift length ≈ 120 cm • 850 kg target • Drift field ≈ 1 to 5 kV/cm • Charge LEM readout: Single electron gain ≈ 103 to 104 • Global light readout collection efficiency ≈ 5% • Single photon detection See Talk by L. Kaufmann at this conference

  30. 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

  31. 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: s = 1.6 x 10-43 cm2 at MW = 60 GeV • Large (>1ton) detectors needed for discovery (s = 10-46 cm2) . 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!

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