G. Gerbier Chinese-french workshop CPPM Marseille sept 2005 Dark Matter : overview of direct searches G. Gerbier CEA/Saclay, DAPNIA -Dark Matter WIMP motivations -Direct detection methods, few experiments outlined -Last news from TAUP conference (september 2005) -Dark objects : from 1930 to now

G. GerbierDark Matters – Bruxelles May An “Extravagant universe” after WMAP (+ HST + SDSS + …) Ω tot = 1.00 ± 0.02 Ω baryon = ± Ω matter ≈ 0.23 Ω  ≈ 0.73 “Concordance model”

G. GerbierDark Matters – Bruxelles May Motivations 1 for non-baryonic Dark Matter “Dark” matter halo around our galaxies => : Local density:  DM ~ GeV/cm3 Astrophysical measurements : - dynamics of clusters (1930), of galaxies Models of structure formation

G. GerbierDark Matters – Bruxelles May Long lived or stable particles left over from the BB with“ weak“ cross section provides right  Weakly Interactive Massive Particles The “WIMP miracle” actual abundance thermoequilibrium abundance Motivations 2 for non-baryonic Dark Matter

G. GerbierDark Matters – Bruxelles May Motivations 3 for non-baryonic Dark Matter  Stable if R-parity is conserved  M > 50 GeV from searches at colliders gaugino fraction: n SUSY theories provides a „natural“ candidate with the LSP neutralino => Picture of the halo of WIMP‘s or  around our galaxy n We (solar system) are sweeping this isothermal cloud at a speed of 220 km/sec

G. GerbierDark Matters – Bruxelles May Can our local Dark Matter be baryonic DM ? –MACHO’s –Cold gas –Black holes Not the solution of the problem…

G. GerbierDark Matters – Bruxelles May Detection : direct, indirect methods Direct detection on earth : –WIMP scattering off nuclei –Low energy keV –Low expected rates < 0.1 evt/kg/day Indirect detection: –Detection of WIMP annihilation products : neutrino, gamma, positron, antiproton,

G. GerbierDark Matters – Bruxelles May A challenge : strategies for direct detection identification In all cases go underground to protect from cosmic rays 1. Reduce radioactivity of materials 2. Use property of nuclear recoil vs electronic energy deposition to establish discrimination method against radioactive background (2 – 3 parameters) 1.evt /evt : cryogenic detectors, liquid noble gases 2.statistical : scintillators 3. Use self shielding to reject elec/neutron backgrounds 1.large mass or 2.large # of detectors 4. Search for annual modulation of signal (signature) 5. Directional measurement: gazeous detectors (signature)

G. GerbierDark Matters – Bruxelles May Direct detection techniques (liquid, solid targets) WIMP Heat Ionization Light Ge Liquid Xe, Ar NaI, Xe Ge, Si CaWO 4, BGO, Al 2 O 3 Al 2 O 3, LiF Elastic nuclear scattering ≈ few % detected energy usually fast no surface effects ? ≈ 100% detected energy relatively slow requires cryogenic detectors ≈ 20 % energy very pure

G. GerbierDark Matters – Bruxelles May Current and future experiments No nuclear recoil discrimination CUORICINO/CUORE42 kg – 760 kg Te02, cryoGran Sasso HDMS0.2 kg Ge in 2.5 kg GeGran Sasso IGEX2 kg GeCanfranc Nuclear recoil discrimination : statistical, evt/evt NaIAD, ANAIS kg NaIBoulby/Canfranc DAMA/LIBRA + ann mod kg NaIGran Sasso ZEPLIN I to III4 kg liq Xe, up to 1 tonBoulby KIMSCsI (Tl), 80 kg in 2003Yang Yang (700 m) EDELWEISS-I and -II1, 10 to 35 kg Ge, cryoFréjus Lab (LSM) CDMS-I and -II1, 10 kg Ge and Si, cryoStanford, Soudan mine CRESST-II10 kg CaWO4, cryoGran Sasso ROSEBUD0.1-1 kg BGO (CaWO4,…), cryoCanfranc Directional, discriminating but digital, and other experiments DRIFTCS2 directionalBoulby SIMPLE/PICASSOFreon areogels, digitalRustrel, SNOLAB Future Super CDMS USFew 100 kgSNOLab EURECA EU100 to 1000 kg?? XENON/XMASS US/JapanFew 100 kgGran Sasso, SuperK ArDM, WARP100 to 1000 kg??

G. GerbierDark Matters – Bruxelles May ELEGANTS, LiF XMASS (SK) CDMS (Soudan) ZEPLIN-II -III XENON CryoArray MAJORANA EDELWEISS (Fréjus) CRESST, HDMS/GENIUS DAMA/LIBRA, WARP CUORICINO/CUORE (Gran Sasso) ZEPLIN, NaIAD, DRIFT (Boulby) IGEX ROSEBUD ANAIS (Canfranc) KIMS (YY) Wimp direct detection experiments (underground sites mandatory, about 10 running in the world) PICASSO SuperCDMS (SNOLab)

G. GerbierDark Matters – Bruxelles May Germanium diodes (IGEX, Heidelberg-Moscow) High purity: best intrinsic background level ~ 0.05 evt/kg/keV/day (Heidelberg-Moscow, Gran Sasso) ~ 0.21 evt/kg/keV/day (IGEX, Canfranc), lower E threshold Present sensitivity limited to ≈ pb after ≈ 20 years of developments 1) Reduce activity of materials

G. GerbierDark Matters – Bruxelles May CEA-Saclay DAPNIA (HEP) CEA-Saclay DRECAM (Cryo) CRTBT Grenoble(Cryo) CSNSM Orsay (Nucl Phys, sol state phys) IAP Paris (Astro) IPN Lyon (Nucl Phys, HEP) FZ-Karlsruhe and Univ. Karlsruhez (HEP) JINR Dubna (Nucl Phys) …in LSM or Fréjus lab 2) Discrimination evt/evt with 2 parameters : heat/ionisation 4800 mwe -  flux = 4/m 2 /d - neutron flux = /s/cm 2

G. GerbierDark Matters – Bruxelles May Cryostat and shield Dilution unit 3 He - 4 He Ge 320 g bolometer at 20 mK 3 bolometers of 320g Nitrogen Hélium Pb/Cu EDELWEISS I = 1 kg

G. GerbierDark Matters – Bruxelles May Germanium crystal WIMP NTD R(T) Al electrodes Heat signal Etot Ionisation signal Ei Phonons Ge nuclear recoils  / electrons Ionisation: e_h pairs Q = Ei/Etot is larger for than for Principle of operation of double signal Ge bolometers

G. GerbierDark Matters – Bruxelles May Co 252 Cf 60Co calib Clean data no event below Q=0.7 Data : shown 22.6 kg.d out of total 60 kg.d - No evidence for signal - Probable surface event contamination at Q<0.7 - Presence of neutrons (1 double) Neutron calib, Expected region for nuclear recoils Edelweiss I data

G. GerbierDark Matters – Bruxelles May EDELWEISS-1 results : 62 kg.d fiducial exposure 59 events, most at low E V. Sanglard et al., PRD71, (2005)

G. GerbierDark Matters – Bruxelles May He tank 20 cm lead shielding Detection volume 50l Copper 10 layers of 12 detectors of 320 g July GG EDELWEISS II up to 36 kg (110 detectors) funded for 9 kg start data taking spring 2006

G. GerbierDark Matters – Bruxelles May EDELWEISS-II installation in LSM rails insert cryostat here mobile 20 cm Pb  shielding (30t, archaeological Pb lining) 50 cm (30t) PE as neutron moderator

G. GerbierDark Matters – Bruxelles May CDMS-II (US) :best sentivity as of sept 2005 Detectors = Ge cryo, ZIPs, Z sensitive 250 g Ge or 100 g Si crystal 1 cm thick x 7.5 cm diameter Collect athermal phonons: XY position imaging Surface (Z) event veto based on pulse shape risetime Measure ionization in low-field (~volts/cm) with segmented contacts to allow rejection of events near outer edge Q outer Q inner z y x X Y Z-sensitive Ionization and Phonon-mediated©

G. GerbierDark Matters – Bruxelles May CDMS results October January 2004: 4 Ge (1 kg) and 2 Si (0.2 kg) ZIPs  and electron rejection both better than proposal 62 “raw” livedays, 53 livedays after cutting times of poor noise, etc. providing 19.4 kg×d Ge (10-100keV)

G. GerbierDark Matters – Bruxelles May Works with many absorber materials CaWO 4, PbWO 4, BaF, BGO (other tungstates and molybdates) Appl. Phys.Lett. 75(9),1335(1999) CRESST-II experiment (Gran Sasso) separate calorimeter as light detector light reflector W-SPT scintillator W-SPT 2) Use of scintillation light (+phonon) for rejection

G. GerbierDark Matters – Bruxelles May ) liquid scintillators : Xe ZEPLIN-I, II, III Xe * +Xe Xe 2 * Triplet 27ns Singlet 3ns 2Xe 175nm Xe ** + Xe Xe 2 + +e - (recomb- ination) Xe + +Xe Ionisation Excitation Electron /nuclear recoil ZEPLIN 1 (3kg, only pulse shape analysis) => not very convincing results

G. GerbierDark Matters – Bruxelles May The WARP 2.3 l test (Wimp ARgon Program, C Rubbia et al.) PMTs PEEK Supports Cathode Grids Waveshifter/Reflector Schematic view of the 2.3 liters chamber  The 2.3 liters liquid Argon prototype is equipped, with 3” PMs made of low background materials.  The structure is a (down) scaled version of the 100 liters detector, with field-shaping electrodes and gas to liquid extraction and acceleration grids. New result given at TAUP 2005

G. GerbierDark Matters – Bruxelles May In the picture below two signals (A and B) from minimum ionising event and a recoil nucleus, respectively. Events are characterized both by the primary (S1) of secondary (S2) amplitudes ratio and by the rising time of the S1 signal. Minimum ionising particles are characterised by high S2/S1 ratio (~100) and by slow S1 signal.  particles and Ar recoils (R-like events) are characterised by low (<5) S2/S1 ratio and fast S1 signal. Discrimination technique Recoil nucleus Minimum ionising particle Time (  s) Amplitude (a.u.) 100 (A) (B) S2 S1 S2 S1 Sum of PMT output after preamplifier

G. GerbierDark Matters – Bruxelles May Complete agreement up to an observed level of ≈ 1/20000  combined rejection < 1/10 8 No event outside the two circled regions  ’s and  ’s  ’s Ar recoils (expected) Ar recoils (expected) The combination of a selection based on S2/S1 ratio and rise time of primary scintillation gives an extremely poweful rejection power for the search of WIMPs signals.

G. GerbierDark Matters – Bruxelles May Drift time (  s) Primary scintillation (phe) The picture shows the primary scintillation light (in phe) of all the selected Recoil-like data, along the drift time The total triggers analyzed are 6.5 millions; 190 R-like events are selected inside the fiducial volume; 388 inside the cathode region. R-like events show a peculiar energy distribution along the drift volume with a characteristic clustering on the cathode region We show that 1)R-like events on the cathode are mostly induced by 222 Rn and its daughters 2)R-like events inside the fiducial volume are induced by environmental neutrons 2.3 liters chamber: analysis of Recoil-like events Fiducial Volume Cathode region Data recorded during 13.4 days of live time in the run done in june 2005 have been scanned looking for Recoil-like events. Recoils from neutrons in LNGS

G. GerbierDark Matters – Bruxelles May Red points: R-like events inside fiducial volume (13.4 days live time) Black histogram: Expected signal from Montecarlo simulation of environmental neutrons in the LNGS laboratory (input neutron spectrum from ref. Astrop.Phys. 22(2004) 313). Uncertainty is of the order of 20%. Blue histogram: expected residual signal from 222 Rn decays on the detector lateral walls Energy (keV) Light yield=0.7 phe/keV Preliminary 2) R-like signals induced by neutrons The plot shows the energy distribution of all R-like events inside the fiducial volume recorded during 13.4 days of live time in June 2005, assuming a light yield of 0.7 phe/keV for recoils as deduced from the analysis of 222 Rn signals. Both the event rate and the shape of the energy spectrum are compatible with the expected events induced by environmental neutrons inside the underground area. counts

G. GerbierDark Matters – Bruxelles May Cylindrical volume, drift length ≈ 120 cm 850 kg target Drift field ≈ 4 kV/cm Charge readout at top: LEM gain ~700 Light readout collection efficiency ≈ 1% Single photon detection Assumed baseline parameters: Light readout Field shaping Reflecting VUV mirror Perforated cathode Charge extraction from LAr to GAr, amplification and readout ArDM 1 T prototype (A Rubbia)

G. GerbierDark Matters – Bruxelles May Annual modulation test by DAMA => First WIMP candidate NaI PMT Gran Sasso Lab, 3500 mwe 9 crystals for ≈ 100kg NaI(Tl) Scintillation detectors with N 2 flow Looking for annual modulation

G. GerbierDark Matters – Bruxelles May A first WIMP candidate: DAMA Data taking completed in July 2002 Total exposure of 107,731 kg.d See annual modulation at 6.3  Claim model-independent evidence for WIMPs in the galactic halo WIMP candidate under standard halo parameters: M  = ( ) GeV and   = ( ) pb Controversial result –Raw spectrum shape (applied cuts ?) –Calibration (resolution better than poissonian at LE) –Residual radioactive background spectrum shape A lot of theoretical engineering to reconcile with others… 2nd phase 250 kg LIBRA running, will conclude ??

G. GerbierDark Matters – Bruxelles May CDMS kg.d  < pb Present and Outlook „10-50 kg-Phase“: 100 times more statistics than EW-1 shielding against neutrons => from materials (Pb) => from rock (Pb+PE) => from DIS muons (veto) „100kg- 1t-Phase“: European scale  EURECA = EDW+CRESST  ZEPLIN max (UK) ? World  XMASS, ArDM, WARP... DAMA I-IV

G. GerbierDark Matters – Bruxelles May Conclusions Intense current and projected experimental activity to tackle heavy WIMP’s hypothesis : no discovery yet… Current direct detection WIMP experiments at last sensitive to (optimistic) SUSY models (≈ pbarn) : Next generation experiments => ≈ few pbarn : Testing the bulk of SUSY parameter space :down to pbarn will require experiments in the one-ton range Indirect detection (neutrino) complementary for spin-dependent couplings LHC together with direct/indirect detection experiments will hopefully allow to pinpoint DM within the next ≈ 10 years Keep an eye on the others : axion… Flash back on the 1930’s…

G. GerbierDark Matters – Bruxelles May Dark matters in 1930’s Missing stuff in beta decay –=> Pauli puts forward the « neutrino », keep ener. cons. –Only detected in 1956 –Mass evidenced in 2000 Missing stuff in the sky –=> Zwicky puts forward «dark matter» –Confirmed missing mass in galaxies by V Rubin in 1970 –Confirmed missing mass by lensing in 1990’s –But recent cosmological view does not bring light –We live in Dark Matters… New data desperately needed…

G. GerbierDark Matters – Bruxelles May Evolution of 60 GeV Rapid evolution of sensitivity of cryogenic experiments (CDMS, CRESST and EDELWEISS) Goals are still 3 orders of magnitude beyond present best performances

G. GerbierDark Matters – Bruxelles May ) Large mass, self VETO, liquid Xenon XMASS next 800kg detector for DM search DM search 642-2” PMTs ≈ 80% photo-coverage ~7 p.e./keV “Full” photo-sensitive “Spherical” geometry 80cm center 5keV 10keV Low energy threshold (100 kg)

G. GerbierDark Matters – Bruxelles May ) EURECA (Edelweiss + CRESST) : 1-ton scale cryogenic expt with 1000 detectors Large A favored by A 2  2 dependence 1 ton Ge more sensitive than 1 ton CaWO4 (W) … but possible comparison of W and Ca+O rates highly interesting Best: compare Ge and CaWO4

G. GerbierDark Matters – Bruxelles May Experimental status, prospective and SUSY theoretical predictions after dmtools R. Gaistkell and V. Mandic CDMS-II, CRESST-II, EDELWEISS-II, XENON, XMASS … sensitivity goals 1 Ton sensitivity goal (optimistic) CRESST, EDELWEISS CDMS present sensitivity Testing all SUSY parameter space (MSSM) requires still 3 orders of magnitude beyond present best performances