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Direct Dark Matter Searches

Direct Dark Matter Searches. Véronique SANGLARD UCBL-CNRS/IN2P3/IP N L sanglard@ipnl.in2p3.fr. Outline. Motivations for non-baryonic dark matter search Principle of the direct detection Running experiments Future experiments Conclusion. Motivations for Dark Matter Search (1).

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Direct Dark Matter Searches

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  1. Direct Dark Matter Searches Véronique SANGLARD UCBL-CNRS/IN2P3/IPNL sanglard@ipnl.in2p3.fr

  2. Outline • Motivations for non-baryonic dark matter search • Principle of the direct detection • Running experiments • Future experiments • Conclusion V. SANGLARD Rencontres de Moriond 2005 « Very High Energy Phenomena in the Universe » La Thuile 18/03/05

  3. Motivations for Dark Matter Search (1) • Rotation curves studies • Dark matter halo around the galaxies • Local density : 0.3 GeV/cm3 V. SANGLARD Rencontres de Moriond 2005 « Very High Energy Phenomena in the Universe » La Thuile 18/03/05

  4. Motivations for Dark Matter Search (2) • At cosmological scale : Results of WMAP -> • Ω tot~ 1.00 • Ω baryon< 0.05 (confirmed by experiments like EROS, MACHO) • Ω matter ~ 0.3 • Ω Cold Dark Matter ~ 0.22 • Need weakly interacting non-baryonic massive particles … WIMP (σ<10-6 pb) V. SANGLARD Rencontres de Moriond 2005 « Very High Energy Phenomena in the Universe » La Thuile 18/03/05

  5. DAMA SUPER K EDELWEISS AMANDA ANTARES ZEPLIN CDMS Natural WIMP candidate • Neutralino definition in the SUSY field • Stable particle if R-parity • conserved (LSP) • Indirect detection : • Detection of WIMPs annihilation • products • Direct detection : • Detection of WIMPs scattering off nuclei V. SANGLARD Rencontres de Moriond 2005 « Very High Energy Phenomena in the Universe » La Thuile 18/03/05

  6. Direct Search Principle • Detection of the energy deposit due to elastic scattering on nuclei of detector in laboratory experiment • Optimum sensitivity for MWIMP ~ MRECOIL • Rate < 1 evt/day/kg of detector • Need low background • Deep underground sites • Radio-purity of components • Active/passive shielding • Need large detector mass (kg -> ton) • Recoil energy ~ 20 keV • Need low recoil energy threshold V. SANGLARD Rencontres de Moriond 2005 « Very High Energy Phenomena in the Universe » La Thuile 18/03/05

  7. WIMP signatures • Nuclear recoils • Not electron recoils (dominant background) • Neutron scattering also produces recoils … • spectrum shape • Exponential (as most bkg) • Shape for backgrounds : unknown/poorly predicted • Coherent interaction (Spin-independent) ? • Absence of multiple scattering (against neutron) • Uniform rate throughout volume (against surface radioactivity) • Directionality of nuclear recoils • Annual rate modulation V. SANGLARD Rencontres de Moriond 2005 « Very High Energy Phenomena in the Universe » La Thuile 18/03/05

  8. WIMP Elastic nuclear scattering Ge Ge, Si 10% energy Ionization Target Liquid Xe Heat Al2O3, LiF 100% energyslowestcryogenics Light 1% energyfastestno surface effects CaWO4, BGO NaI, Xe WIMP Direct detection techniques V. SANGLARD Rencontres de Moriond 2005 « Very High Energy Phenomena in the Universe » La Thuile 18/03/05

  9. Current direct detection experiments None Statistical Event-by-event V. SANGLARD Rencontres de Moriond 2005 « Very High Energy Phenomena in the Universe » La Thuile 18/03/05

  10. NaI NaI PMT PMT NaI NaI NaI scintillation : DAMA • Based in Gran Sasso lab (3500 mwe) • 100 kg of NaI(Tl) • Exposure : 107731kg.d • Coincidence between 2 PMTs • Pulse shape rejection inefficient at 2 keVee • Used annual modulation • Claim annual modulation at 6.3σ over 7 annual cycles • Mχ ~ 52 GeV/c² • σn~ 7.2 10-6 pb • Not compatible with CDMS, EDELWEISS experiments • Future = LIBRA (250 kg of NaI) V. SANGLARD Rencontres de Moriond 2005 « Very High Energy Phenomena in the Universe » La Thuile 18/03/05

  11. NaI scintillation : DAMA • Based in Gran Sasso lab (3500 mwe) • 100 kg of NaI(Tl) • Exposure : 107731kg.d • Coincidence between 2 PMTs • Pulse shape rejection inefficient at 2 keVee • Used annual modulation • Claim annual modulation at 6.3σ over 7 annual cycles • Mχ ~ 52 GeV/c² • σn~ 7.2 10-6 pb • Not compatible with CDMS, EDELWEISS experiments • Future = LIBRA (250 kg of NaI) Single-hits events residual rates V. SANGLARD Rencontres de Moriond 2005 « Very High Energy Phenomena in the Universe » La Thuile 18/03/05

  12. Ge ionization : GENIUS-TF • Based in Gran Sasso lab (3500 mwe) • Running experiment • 4x2.5 kg (up to 14) naked HPGe in N2 • Problems surface contamination by Radon • Goal for background : 1 count/(kg.keV.y) < 50 keV • But serious problems for GENIUS (1T of Ge in N2) V. SANGLARD Rencontres de Moriond 2005 « Very High Energy Phenomena in the Universe » La Thuile 18/03/05

  13. Xe+ Ionization +Xe Electron/nuclear recoil Xe2+ Excitation +e- (recombination) Xe* Xe** + Xe +Xe Xe2* 175nm 175nm Triplet Singlet 3ns 27ns 2Xe 2Xe Liquid Xe Scintillation : ZEPLIN-I • Based in Boulby mine (2800 mwe) • 3.2 kg (fid.) -> 230 kg.d • Single phase • 3 PMTs coincidence • Pulse Shape Amplitude (time constant discrimination) • Difficulties with neutron calibration at low energy (in deep site) • Resolution 100% at 40 keV (7 keVee) • Experiment now completed but no published results yet • Future : ZEPLIN II (30 kg)Ionization+scintillation V. SANGLARD Rencontres de Moriond 2005 « Very High Energy Phenomena in the Universe » La Thuile 18/03/05

  14. Liquid Xe Scintillation+Ionization : XENON • Prototype 3kg (active mass) dual phase detector with TPCs • 7 PMTs in the cold gas above the liquid • Measurements of • Primary scintillation light (S1) • Secondary scintillation light from ionization electrons (S2) • CsI photoelectron signal (S3) • Discrimination variable S1/S2 • Current work • Calibrations (γ, α, neutrons) • Future : XENON10,100,1T in Gran Sasso lab S1 S3 S2 V. SANGLARD Rencontres de Moriond 2005 « Very High Energy Phenomena in the Universe » La Thuile 18/03/05

  15. First plot showing neutron calibration with Liquid Xe Electronic recoils Nuclear recoils Simulation of detector response for neutron calibration Liquid Xe Scintillation+Ionization : XENON • Prototype 3kg (active mass) dual phase detector with TPCs • 7 PMTs in the cold gas above the liquid • Measurements of • Primary scintillation light (S1) • Secondary scintillation light from ionization electrons (S2) • CsI photoelectron signal (S3) • Discrimination variable S1/S2 • Current work • Calibrations (γ, α, neutrons) • Future : XENON10,100,1T in Gran Sasso lab V. SANGLARD Rencontres de Moriond 2005 « Very High Energy Phenomena in the Universe » La Thuile 18/03/05

  16. Phonon and scintillation/ionization bolometers • Simultaneous measurement of phonon and scintillation/ionization • Different (light or charge)/heat ratio for nuclear and electron recoils (WIMP and neutron have lower light/charge than γs, βs ) • Discrimination event-by-event of electron recoils (main background) V. SANGLARD Rencontres de Moriond 2005 « Very High Energy Phenomena in the Universe » La Thuile 18/03/05

  17. Heat-scintillation : CRESST-II • Based in Gran Sasso lab (3500 mwe) • 2x300g CaWO4 crystal +W-SPT • Net exposure: ~ 20.5 kg.d • Rejection at 15 keV: 99.7% • No neutron shield installed • WIMP interact mainly with W • Energy range: 12-40 keV separate cryogenic light detector W SPT (W-Superconducting Transition Thermometers) absorber : V. SANGLARD Rencontres de Moriond 2005 « Very High Energy Phenomena in the Universe » La Thuile 18/03/05

  18. Heat-scintillation: CRESST-II 90% of nuclear recoils with quenching factor Q=7.4 below this line 90% of nuclear recoils with Q=40 (W) below this line 0 events (between 12 and 40keV) Only this detector used to derive exclusion limits V. SANGLARD Rencontres de Moriond 2005 « Very High Energy Phenomena in the Universe » La Thuile 18/03/05

  19. FET cards 4 K SQUID cards 0.6 K 0.06 K 0.02 K ZIP 1 (Ge) ZIP 2 (Ge) ZIP 3 (Ge) ZIP 4 (Si) ZIP 5 (Ge) ZIP 6 (Si) Heat-ionization: CDMS-II • Based in Soudan Underground lab (2090 mwe) • 4x250g Ge + 2x100g Si • Net exposure: 19.4 kg.d • Detector = ZIP (sensitive to athermal phonon) • Active muon veto + shielding (PE + Pb) V. SANGLARD Rencontres de Moriond 2005 « Very High Energy Phenomena in the Universe » La Thuile 18/03/05

  20. Heat-ionization: CDMS-II • Rejection of background surface events with timing cuts 0 events (between 10-100 keV) V. SANGLARD Rencontres de Moriond 2005 « Very High Energy Phenomena in the Universe » La Thuile 18/03/05

  21. Heat-ionization: EDELWEISS-I • Based in Modane Underground laboratory (4800 mwe) • Low radioactivity dilution cryostat at 17 mK • Shielding : PE+Pb+Cu • 3x320g Ge • Amorphous layer (Ge/Si) • NTD Ge thermometric sensor • Al electrode (one segmented) • Fiducial volume: 57% • Rejection-γ 99.9% at 15 keV 3x320g heat-and-ionization Ge cryogenic detectors V. SANGLARD Rencontres de Moriond 2005 « Very High Energy Phenomena in the Universe » La Thuile 18/03/05

  22. Heat-ionization: EDELWEISS-I • New data taking with trigger on phonon signal • Improved efficiency at low energy (50 % at 11 keV) • Fiducial exposure: 22 kg.d • Stable behavior over 4 months • 18 nuclear recoil candidates > 15 keV • 1 n-n coincidence • Possible backgrounds • Residual neutron flux • Miscollected charge events • Not enough statistics to conclude V. SANGLARD Rencontres de Moriond 2005 « Very High Energy Phenomena in the Universe » La Thuile 18/03/05

  23. Heat-ionization: EDELWEISS-I • Final results: 62 kg.d (fid. exp.) • 50% trigger efficiency at 15 keV • 40 nuclear recoil candidates > 15 keV (only 6 > 30 keV) • Unknown background • Used method developed by S. Yellin to derive exclusion limits (as CDMS) • No background subtraction • New limits consistent with previous published results • V.Sanglard et al. astro-ph/0503265 (to PRD) • Experiment stopped in March 2004 V. SANGLARD Rencontres de Moriond 2005 « Very High Energy Phenomena in the Universe » La Thuile 18/03/05

  24. 90% C.L. exclusion limits on WIMP-nucleon scattering cross-section (spin-independent) Only published results are reported V. SANGLARD Rencontres de Moriond 2005 « Very High Energy Phenomena in the Universe » La Thuile 18/03/05

  25. Next step for running experiments • CDMS-II • 7 towers (=4x250g Ge + 2x100g Si) • 2 running now • CRESST-II • 33x300g CaWO4 • Wiring to mK level • New readout system • Neutron shielding + μ veto • EDELWEISS-II • Next slide V. SANGLARD Rencontres de Moriond 2005 « Very High Energy Phenomena in the Universe » La Thuile 18/03/05

  26. EDELWEISS-II • Low radioactivity cryostat with larger experimental volume (50 liters) • Improved neutron shielding • Addition of μ veto • 1st phase: 28 detectors (21x320g Ge+7x400g NbSi) • Up to 120 detectors • Expected sensitivity: 0.002 evt/kg/day • Installation in progress in LSM V. SANGLARD Rencontres de Moriond 2005 « Very High Energy Phenomena in the Universe » La Thuile 18/03/05

  27. Conclusion • Today: 10-6 pb era • Starting to test most optimistic SUSY models • Next step: 10-8 pb • Increased detector mass • Further reduce background rejection • Lower energy threshold • Improve event-by-event discrimination • Goal: 10-10 pb within 10 years • Probe most of the allowed SUSY parameter space • 1 ton scale (SuperCDMS, EURECA) • Combined several targets V. SANGLARD Rencontres de Moriond 2005 « Very High Energy Phenomena in the Universe » La Thuile 18/03/05

  28. Conclusion • Today: 10-6 pb era • Starting to test most optimistic SUSY models • Next step: 10-8 pb • Increased detector mass • Further reduce background rejection • Lower energy threshold • Improve event-by-event discrimination • Goal: 10-10 pb within 10 years • Probe most of the allowed SUSY parameter space • 1 ton scale (SuperCDMS, EURECA) • Combined several targets V. SANGLARD Rencontres de Moriond 2005 « Very High Energy Phenomena in the Universe » La Thuile 18/03/05

  29. 1 ton : a simple experiment ? V. SANGLARD Rencontres de Moriond 2005 « Very High Energy Phenomena in the Universe » La Thuile 18/03/05

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