Dark matter search with EDELWEISS Recent results and prospects Gilles Gerbier- CEA Saclay/IRFU on behalf of Edelweiss (and CDMS) collaboration(s) and also some personal views PPC2011 CERN -june 15th 2011 1 Expérience pour DEtecter Les Wimps En SIte Souterrainn Outline Edelweiss : “ID technology”, results of 1 year run Combination of data with CDMS : results Prospects of Edelweiss for 2012-2013 Low mass WIMP’s : new result, comments wrt CoGeNT Further future : EURECA @ ULISSE Principle of WIMP direct detection WIMP Galactic WIMP Interaction in a terrestrial detector velocity v ~ 200 km/s θr local density ρ0 Energy deposition Nuclear recoil Er • Relevant parameters: - mass mχ ~ 10 GeV to 10 TeV for usual extensions of the Standard Model - WIMP-nucleon cross-section σ, weakly 1 evt / kg / yr contrained but of the order of EW scale • Non-relativistic diffusion: 1 evt / ton / yr ~ 1 - 100 keV • Interaction rate: 0 v 100 100 GeV 0 0 v0 1 1 R ~ ~ 0.04 8 3 1 kg day m mN A m 10 pb 0.3GeV cm 230 km s 3 Principle of WIMP direct detection WIMP Galactic WIMP Interaction in a terrestrial detector velocity v ~ 200 km/s θr local density ρ0 Energy deposition Nuclear recoil Er • Low-threshold detectors • Relevant parameters: • Ultra-low-background detectors : - mass mχ ~ 10 GeV to 10 TeV for usual extensions of the Standard Model- « Passive » bckgd reduction (shields, - WIMP-nucleon cross-section σ, weakly 1 evt / kg / yr contrained but of the order ofradiopurity, EW scale external vetos..) - « Active » bckgd reduction • Non-relativistic diffusion: (discrimination of electron recoils, multiple scatters..) 1 evt / ton / yr ~ 1 - 100 keV • We consider only the « spin- • Interaction rate: independent » channel here → single 0 v 100 100 GeV WIMP-nucleon0 0 cross-sectionv0 ∀ target1 1 R ~ ~ 0.04 8 3 1 kg day m mN A m 10 pb 0.3GeV cm 230 km s 4 The EDELWEISS collaboration Oxford - sep 10 Karlsruhe - oct 09 FRANCE ITALIE • CEA Saclay (IRFU and IRAMIS) 4800 mwe LSM (Fréjus) • CSNSM Orsay (CNRS/IN2P3 + Univ. Paris Sud) Altitudes 1228 m 1263 m 1298 m • IPNLyon (CNRS/IN2P3 + Univ. Lyon 1) Distances 0 m 6210 m 12 868 m • Institut Néel Grenoble (CNRS/INP) • Karlsruhe Institute of Technology • JINR Dubna 131 km • Oxford University (joined in 2009) from here • Sheffield University (joined in 2010) The EDELWEISS-II infrastructure Cryogenic installation (18 mK) : Reversed geometry cryostat, pulse tubes Remotely controlled Can host up to 40kg of detectors Shieldings : Clean room + deradonized air Active muon veto (>98% coverage) 50-cm PE shield 20-cm lead shield ⇒ γ background reduced by ~3 wrt EDW1 Other items: Remotely controlled sources for gamma calibrations + regenerations AmBe sources of neutron calibrations Detector storage & repair within the clean room 3 Radon detector down to few mBq/m He3 neutron detector (thermal neutron monitoring inside shields) sensitivity ~10-9 n/cm2/s Liquid scintillator neutron counter (study of muon induced neutrons) 6 The EDELWEISS-II infrastructure Cryogenic installation (18 mK) : Reversed geometry cryostat, pulse tubes Remotely controlled Can host up to 40kg of detectors Shieldings : Clean room + deradonized air Active muon veto (>98% coverage) 50-cm PE shield 20-cm lead shield ⇒ γ background reduced by ~3 wrt EDW1 Other items: Remotely controlled sources for gamma calibrations + regenerations AmBe sources of neutron calibrations Detector storage & repair within the clean room 3 Radon detector down to few mBq/m He3 neutron detector (thermal neutron monitoring inside shields) sensitivity ~10-9 n/cm2/s Liquid scintillator neutron counter (study of muon induced neutrons) 7 « EDELWEISS-I-like » detectors Germanium bolometers Ionization measurement @ few V/cm Heat measurement (NTD sensor) @ 20 mK: heat signal = k x recoil energy + Luke effect Discriminating variable between electronic and nuclear recoils : « Q » = ionization/recoil energy ⇒ Full separation between ER and NR electron recoils inelastic neutron diffusion Neutron calibration (S. Scorza PhD thesis) nuclear recoils 8 « EDELWEISS-I-like » detectors Germanium bolometers Ionization measurement @ few V/cm Heat measurement (NTD sensor) @ 20 mK: heat signal = k x recoil energy + Luke effect Discriminating variable between electronic and nuclear recoils : « Q » = ionization/recoil energy ⇒ Full separation between ER and NR Surface interactions Population identified as originating from 210Pb at surface of detector or Cu cover 9 Rejecting surface events with interleaved electrodes ‘a’ electrodes (+4V) the « ID » (InterDigit) detector collecting ‘b’ electrodes (-1.5V) field shapping fiducial volume First 200g ID • Keep the EDW-I NTD phonon ‘c’ (-4V) ‘d’ (+1.5V) detector • Modify the E field near the - First detector built 2007 surfaces with interleaved - 1x200g + 3x400g tested in 2008 electrodes - 10x400g running 1 year 2009-2010 • Use ‘b’ and ‘d’ signals as vetos - 800g detectors tested and running 2010-2011 against surface events (NB : an alternative solution, NbSi films, studied for 10 years was abandoned in 2007) 10 Ionization yield for surface events 210Pb calibration (2008) Background data 6x104 210Bi 6x104 210 6x104 Po 210Pb 1 evt PLB 681 (2009) 305-309 [arXiv:0905.0753] Much better than anticipated ! 11 WIMP search with ID-400 detectors 1) ~ 20 kg.d in 2008 during validation runs of 2 ID detectors 2) Physics run Apr 2009 - May 2010 (10 detectors) : ~ 380 kg.d Published : 2008 + 6 months 2009 = 160 kg.d - PLB 687 (2010) 294–298 [arXiv: 0912.0805] Final results of the complete run presented here - submited [arXiv:1103.4070] All heat sensors working 55/60 electronics channels working calibrations show we can use all detectors for WIMP search thanks to redundancy Fiducial zone ~170g 12 ID-400 : gamma calibration • Regular calibrations between background runs with two motorized 133Ba sources (356 keV) • all IDs stacked • same analysis/cuts as for bg data • more than 350 000 fiducial evts • anomalous events observed: - for 20<E<200keV ~ (3±1)x10-5 rejection - study of possible mechanisms under way – probably related to the large non-fiducial volume 13 WIMP search : first six month result 160 kg.d x 90% NR band = 144 kg.d X 15 « WIMP candidate » Er = 21 keV coincidences bolo-bolo+veto => muon-induced neutrons in fiducial volume PL B 687 (2010) 294–298 [arXiv:0912.0805] 14 WIMP search : final results fiducial volume events, 427 kg.d Five WIMP candidates: - four 20.8 < E < 23.2 keV - one @ 172 keV « alpha tail » 15 Elastic WIMP scattering limit Fiducial exposure 384 kg.d 4.4 x 10-8 pb at Mχ=85 GeV (x2.7 better than 2009 result, 35 x better than 2003) Sensitivity limited at low mass due to background Backgrounds arXiv:1103.4070 16 Elastic WIMP scattering limit Fiducial exposure 384 kg.d 4.4 x 10-8 pb at Mχ=85 GeV (x2.7 better than 2009 result, 35 x better than 2003) Sensitivity limited at low mass due to background Backgrounds arXiv:1103.4070 17 Inelastic dark matter δ=0 Dark matter modulated signal claimed by DAMA/LIBRA vs. null detection in all the other direct detection experiments χ + m => χ* + m (δ~100 keV) δ=60 1 1 mE R vmin 2 c 2mE R _ _ _ _ _ _ _ v el min Signal globally reduced and suppressed at low recoil energies δ=120 Heavier targets preferred Modulation is enhanced A. Torrento / CEA-Saclay 18 Constraints on inelastic dark matter arXiv:1103.4070 Ana Sofia Torrento analyis same data & analysis as in the elastic case use vesc = 544 km/s (RAVE survey, arXiv:0611671, 2007) DAMA allowed region excluded for Mχ > 90 GeV (90%CL) 19 Elastic WIMP scattering limits : similar sensitivities from CDMS and Edelweiss Limits very close with identical nucleus : why not combine data ourselves before others do ? arXiv:1103.4070 20 Combining Germanium data CDMS+EDELWEISS : the data “Simple merger method” More sophisticated ones also used in paper Quite good spirit and efficiency to complete analysis in few months CDMS+EDELWEISS : the limits 1 TeV: x2 behind Xe100 100 GeV: x3 behind Xe100 Below 70 GeV: >x5 behind Xe100 Edelweiss III : new detectors FID800 (2010) Fiducial mass ~640g • All fiducial volume: more Preliminary statistics than stacked ID-400 statistics • No event in NR • Expected to be and indeed better than IDs ! ID (350000 γ) 24 Towards 5x10-9 pb : EDELWEISS-III Program under way, funded Infrastructure : Upgrades of cabling, cryogenics, acquisition and shielding within the current EDW-II setup Special care with neutrons : additionnal inner PE shield Detectors : ~ 40 FID800 bolometers installed beginning 2012 : 26 kg fiducial ⇒ 3000 kg.d by end 2012 25 Low mass ? Low mass WIMPs ? Need very low threshold Obtained with a « heat only » detector = naked Ge 330 g crystal with one NTD sensor NB : sensitive to full recoil energy (electron/ nuclear) Very high sensitivity obtained Trigger lower than 1.7 keV 90 % of time Select good pulse shapes : risetime/duration 2-8 keV Calibration Data Physical evts Physical evts Typical raw 2 keV pulses Jocelyn Domange thesis Noise 27 Data with 1 detector Care was taken on control of low energy part of spectrum : no electronic noise kept, correct efficiency for physics pulses Quality cuts => 200 days data Software cut @ 2keV Rising spectrum at low energy but : 10 keV comogenics Backgrounds from Zn65 and Ge68 Compton : flat Surface β’s Surface beta’s from 210Pb : from 210Pb rising towards low energy Compton Releases of stress WIMPs ? Yes, possible to fit, but can be as well background 28 Data with 1 detector Care was taken on control of low energy