Cryogenic Detectors Direct Dark Matter Search. Dark Matter

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2 Cryogenic Detectors Direct Search

3 Matter in the Universe - Composition ν too light => most of the is cold Ωmat = u d of so far unknown weakly interacting, massive particles WIMPs normal baryonic matter 0.04 e < ν < 0.02 (HDM) νe from ν oscillations => Σmν > 0.05eV (50GeV~1000GeV Neutralino?)? cold (CDM) 0.23 physics beyond standard model supersymmetry?

4 Cosmic Microwave Background Matter-Density Ωmatter Anisotropy: Angular scale => Wilkinson Microwave Anisotropy Probe Ωtot=1 geometry, Ωtot Intensities => gravitational pote matter densities - gravitation Ωmatter - coupling to radiation Ωbaryon Ωmatter = 0.27 => Ωmatter Ωlum 0.01 mostly Ωbaryon = u e d => Ωmatter >> Ωbaryon

5 Structure in the Universe and Neutrinos Ωmatter ~ 0.30 Ων < 0.02 Ων < 0.02 Σmνi < 1.2eV

6 Matter in the Universe - Composition ν too light => most of the is cold Ωmat = 0.27 ± 0.04 u d of so far unknown weakly interacting, massive particles WIMPs normal baryonic matter 0.04 e < ν < 0.02 (HDM) νe from ν oscillations => Σmν > 0.05eV (50GeV~1000GeV Neutralino?)? cold (CDM) 0.23 physics beyond standard model supersymmetry?

7 WIMP - Direct Detection Weakly Interacting Massive Particles = WIMPs elastic scattering on nuclei nuclear recoils: reduced efficiency of charge or light production - mass 50 GeV - ~ 1000 TeV - relative speed 270 km/s χ only a few kev of energy - cross section σχ < 10-36cm2 - local WIMP-density ρχ 0.3 GeV / cm3 - corresp. 3 WIMPs(100GeV) / liter /s /cm2 very very rare scattering events (< 1 / week / kg)

8 WIMP Direct Detection - Signal and Background Detector rate, spectrum required sensitivity ~ 1 event / kg / week (future experiments even 100 x less) radioactivity: > 1Hz/kg muons ~ 0.1Hz/kg: ~ 106 events /kg /week ~ 105 events /kg /week, => clean shielding: (old) Pb, Cu => needs ~ 1.5 km Rock => Underground-Laboratory

9 WIMP Direct Detection - Underground Laboratory shielding from cosmic rays Soudan Mine USA Modane Gran Sasso Lab

10 WIMP Direct Detection - Experiments Conventional Detectors: DAMA-LIBRA NaI-Scintillation ββ Experiments Ge-Ionisation. Cryogenic Detectors: CDMS Ge-Ionisation-Phonons USA Soudan Mine EDELWEISS Ge-Ionisation-Phonons France, Germany Fréjus-Tunnel CRESST CaWO4-Scintillation-Phonons Germany, UK, Italy Gran Sasso Liquid NobleGas Detectors: ZEPLIN Xe-Scint., Scint.-Ionisation UK Boulby Mine XENON Xe-Scintillation-Ionisation US, Italy, Germany, Portugal Gran Sasso WARP Ar-Scintillation-Ionisation Italy, US, Poland Gran Sasso ArDM Ar-Scintillation-Ionisation Switzerland, Spain, UK, Poland CERN, Canfranc?

11 Sensitivity WIMP Searches conventional: indirect searches: SuperK upward µ liquid Xenon: cryogenic: CRESST 10,5 kg-days CaWO4 30 kgd Ge

12 WIMP Direct Detection - Low Temperature Calorimeter particle absorption => phonons (~heat) phonon-absorption in thermometer => temperature rise low temperatures (~20mK) => high sensitivity, small C high sensitivity to nuclear recoils no quenching thermometer absorber-crystal coupling to heat sink detected particle (WIMP) thermometer types: superconducting phase transition thermometers (SPT) NTD - Ge thermistors (highly doped semiconductors) low energy threshold wide choice of absorber materials

13 Superconducting Phase Transition Thermometer superconducting phase transition thermometer Tungsten Tc 15mK heat capacity Sapphire 250gr 2 MeV / 25mK 130 GeV / 1K Sapphire- or CaWO4 -absorber 250gr, 4cm x 4cm x 4cm CRESST-Collaboration Cryogenic Rare Event Search with Superconducting Thermometers Max-Planck-Institut München, TU München Universität Tübingen, Oxford University, Gran Sasso Lab

14 electromagnetic γ, β nuclear recoils χ e- e- ionisation (charge, scintillation light) phonons only little ionisation

15 Phonon + Charge / Light Measurement => recognize Background χ CRESST II - detectors simultaneous light and phonon measurement thermometer thermometer absorber CaWO4 phonon-detector light detector (low T calorimeter) reflecting foil EDELWEISS-France and Karlsruhe CDMS - US simultaneous charge and phonons (semiconductors Ge, Si)

16 WIMP Direct Detection Event by Event Discrimination EDELWEISS (France) und CDMS (USA) Projects Ioniosation-Phonon 320g Ge-Detector Low Background Data Testmessung mit Neutronen (=> Kernrückstöße) Thermometer Ge 300gr oder Si 300gr Ionisation

17 EDELWEISS - Cryogenic Ge-Detectors Heat / Charge

18 EDELWEISS at Frejus tunnel - Results 2003

19 EDELWEISS - Results kg d EDELWEISS 2002 upgrade done just started 7kg run

20 Heat / Charge - reduced charge collection from surface

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22 EDELWEISS Upgrade Start 2007 able to run up to 100 detectors ~30kg started in 2007 with 30 detectors => expect new results

23 CDMS at Soudan Mine Brown University Case Western Reserve University University of Colorado at Denver Fermi National Accelerator Laboratory Lawrence Berkeley National Laboratory Santa Clara University Stanford University University of California, Berkeley University of California, Santa Barbara University of Florida University of Minnesota

24 CDMS Charge & Phonon Detectors Phonon D SQUID array R bias R feedback I bias 250 g Ge or 100 g Si crystal 1 cm thick x 7.5 cm diameter Photolithographic patterning Phonon sensors: 4 quadrants with each 888 sensors (TES) operated in parallel D A C B z TES: 1-µm-thick strip of W connected to 8 superconducting Al collection fins QQououter ter y x Q inner Q inner Vqbias Measure ionization in low-field (~volts/cm) with segmented contacts to allow rejection of events near outer edge 2 charge electrodes: Inner fiducial electrode Outer guard ring 1 µ tungsten 380µ x 60µ aluminum fins

25 CDMS Timing Cut remove near surface events charge / heat ~ rise time

26 CDMS data 2004/2005 After timing cuts Charge Yield Charge Yield Prior to timing cuts

27 CDMS - Results kg d CDMS 2005 continues to run with ~ 5kg detectors => expect more data

28 CRESST at Gran Sasso Underground Laboratory Max-Planck-Institut München TU München Universität Tübingen Oxford University Gran Sasso Lab

29 CRESST light - heat - particle identification γ α CaWO4 n

30 CRESST at Gran Sasso Underground Laboratory

31 CRESST at Gran Sasso Underground Laboratory

32 CRESST at Gran Sasso Underground Laboratory

33 CRESST 2004 no neutron shield light / heat Run28, 2004, 10.5 kg d 1.5 CaWO4 1.0 crystals as target % O-recoils % W-recoils heat / kev 150

34 Sensitivity WIMP Searches CRESST 2004 now started to run in upgraded and shielded set up expect more data

35 CRESST upgrade more channels neutron shield Shielded cryostat 2007: start to install 10kg of target mass (33 modules) 2004/05: upgrade to 66 channel SQUID array 66 SQUIDs on Heflange 2004: installation of PE neutron moderator shield PE neutron moderator Plastic scintill. µ-veto 2005/06: add muon veto (against muon induced neutrons in the Pb/Cu shield)

36 CRESST neutron shield

37 CRESST SQUID system and detectors

38 CRESST 2007 d) preliminary (only 3kg Licht-/Phononenergie vorläufig, Januar 2007, 3 kg d (Zora) 1.5 with neutron shield and alpha recoil rejection Energie im Phononendetektor / kev

39 Future so far : ~ 1kg targets in preparation: ~ 10kg targets => expect new results soon long term: increase sensitivity 1/week/kg to a few/year/100kg - very very good background control - some 100kg of cryogenic detectors => EURECA Collaboration ECA R EU