CDMS IIUCSB Direct Dark Matter Detection CDMS, ZEPLIN, DRIFT (Edelweiss) ICHEP 31 Amsterdam July 26, 2002 Harry Nelson Santa Barbara

CDMS IIUCSB July 26, 2002 ICHEP 31 - Harry Nelson 2 Several Arguments for Dark Matter Milky Way’s Rotation Curve R  Massive Particle Popular Weak Interactions (WIMP): » Dark/Luminous Balance » SUSY Broken at Weak Scale…  0 (neutralino)  R 220 km/s  Physics Motivation

CDMS IIUCSB July 26, 2002 ICHEP 31 - Harry Nelson 3 WIMP/nucleon  cm Exper. CDMS DAMA Theory SUSY, various constraints including Big Bang

CDMS IIUCSB July 26, 2002 ICHEP 31 - Harry Nelson 4 00 v/c  Nucleus Recoils Dense Energy Deposition v/c small; Bragg Direct Detection  Electron Recoils SignalBackground Neutrons same, but  higher - shield v/c  0.3 Sparse Energy Deposition ErEr ErEr Density/Sparsity Basis of Discrimination

CDMS IIUCSB July 26, 2002 ICHEP 31 - Harry Nelson 5 00 Nucleus Recoils Rate, Energy Spectrum ErEr Silicon, Sulphur Germanium Iodine, Xenon A2A2 M WIMP =100 GeV   cm 2 /nucleon Slope: Maxwell-Boltzmann WIMPs in Galaxy Diffraction off Nucleus

CDMS IIUCSB July 26, 2002 ICHEP 31 - Harry Nelson 6 The Experiments CDMS - Ge/Si, measure ionization (Q) and heat/phonons (P) Recoil/  discrimination: Q/P 2 Detector Types, 2 sites!Updated Result ZEPLIN 1 - Liq Xe, measure scintillation Recoil/  discrimination: Pulse Shape in Time 2 more ZEPLIN’s - add ionization New Result DRIFT - CS 2, measure ionization (Q) Recoil/  discrimination: Spatial Distribution of Q Directionality Edelweiss!

CDMS IIUCSB July 26, 2002 ICHEP 31 - Harry Nelson 7 CDMS Sites polyethylene outer moderator detectorsinner Pb shield dilution refrigerator Icebox outer Pb shield scintillator veto Stanford Site: 16 mwe Substantial neutron flux Results Soudan Site: 2000 mwe Neutron flux down 1/300 Commissioning fridge Operation this winter

CDMS IIUCSB July 26, 2002 ICHEP 31 - Harry Nelson 8 CDMS Detectors `BLIPs’ 1/6 kg disks One Side Ioniz. (Q) Thermistor - Phonons (P) slow Results `ZIPs’ P - ahtermal photons `TES’ - Trans. Edge Sens Fast Signal: x, y, z Performance at Stanford

CDMS IIUCSB July 26, 2002 ICHEP 31 - Harry Nelson 9 CDMS Data (BLIP) 616 Neutrons (external source) 1334 Photons (external source) 233 Electrons (tagged contamination) Inner Ionization Electrode Outer Ionization Electrode Calibration Shared: 4.4 kg-d Inner: 12 kg-d 13 nucl. recoil 10 nucl. recoil Shallow: Neutrons

CDMS IIUCSB July 26, 2002 ICHEP 31 - Harry Nelson 10 Updated Limits Shared Electrode With WIMPs Various Masses Neutron Bkgd

CDMS IIUCSB July 26, 2002 ICHEP 31 - Harry Nelson 11 Explanation, Edelweiss CDMS: shift toward expected (old had `lucky’ bkgd fluctuation) New CDMS Old CDMS Exp. CDMS (dotted) 2002 Edelweiss ! Detectors: similar to CDMS 15.8 kg-d / 16 mwe depth11.7 kg-d / 4800 mwe 0.2% CL for consis- tency with DAMA

CDMS IIUCSB July 26, 2002 ICHEP 31 - Harry Nelson 12 CDMS Status At Shallow Site (16 mwe):  Neutron Shielding Added (reduce 1/2)  Detector Technology Completely Changed  `ZIP’… detect athermal phonons  Pulse faster - microseconds  Pulse Risetime - rejection of external electrons  27 kg-d accumulated, more being gathered  Data Terrific  Results Later This Year Move to Soudan (2100 mwe) ASAP

CDMS IIUCSB July 26, 2002 ICHEP 31 - Harry Nelson 13 Recoil - THz phonons Phonons go to surface SC Al- fins, break Cooper pairs, giving quasiparticles. and create quasiparticles Quasiparticles diffuse in ~  s to W transition-edge sensors (TES) where they release their energy to the W electrons Release energy, T is raised, R is raised Current change is measured with SQUIDs W Al qp-trap Al Collector W TES Electro- Thermal Feedback R T Si or Ge qp diffusion ZIP Detection Mechanism

CDMS IIUCSB July 26, 2002 ICHEP 31 - Harry Nelson 14 surface bulk Nuclear recoils (from neutron source)  External electrons Risetime Discrimination

CDMS IIUCSB July 26, 2002 ICHEP 31 - Harry Nelson 15  = 10.4 keV  = 0.34 keV Recent ZIP Data With Activity in Veto

CDMS IIUCSB July 26, 2002 ICHEP 31 - Harry Nelson 16 ZEPLIN Liquid Xenon  Scale-up to 1000 kg  Scintillates without additives  Pulse Shape - recoil/  discrimination  Zeplin 1 Sensitivity Enhancement  Ionization (Z2/3)  non - PMT + Xe * +Xe Xe 2 * Triplet 27ns Singlet 3ns 2Xe 175nm Xe ** + Xe Xe 2 + +e - (recombination) Xe + +Xe Ionisation Excitation Nuclear/Electron Recoil Prompt Recombination depletes this route for nuclear recoils

CDMS IIUCSB July 26, 2002 ICHEP 31 - Harry Nelson 17 ZEPLIN-1 Boulby in UK mwe depth Active Shield 3 tubes 4 kg L Xe Data Signal Region (Bulk)

CDMS IIUCSB July 26, 2002 ICHEP 31 - Harry Nelson 18 Calibration  1/5 of energy from nuclear recoil appears as scintillation Recoil Energy (keV)  Energy(keV) Range for 100 GeV WIMP

CDMS IIUCSB July 26, 2002 ICHEP 31 - Harry Nelson 19 WIMP Data  Energy(keV) Signal prior to  /nuclear recoil discrimination Counts/(kg day keV) Pulse time constant (ns) nuclear recoil  DATA 90 kg-days

CDMS IIUCSB July 26, 2002 ICHEP 31 - Harry Nelson 20 Zeplin-1 02 CDMS Feb. 02 DAMA Edelweiss 02 Summer 2002 Status

CDMS IIUCSB July 26, 2002 ICHEP 31 - Harry Nelson 21 Zeplin II, III: drift, amplify ionization Primary Scintillation Secondary Scintillation from Drifted, Extracted Ionization Time (like recoil) … nuclear recoil threshold of 5 keV

CDMS IIUCSB July 26, 2002 ICHEP 31 - Harry Nelson 22 Zeplin II (30 kg)Zeplin III (6 kg) Long Term Goal is 1000 kg….

CDMS IIUCSB July 26, 2002 ICHEP 31 - Harry Nelson 23 DRIFT Boulby in UK mwe depth Scattered WIMP Recoil Atom Ionisation drift Electric Field 1 m 3 40 Torr CS 2 (0.17 kg) TPC Suppresses Diffusion (no B field) Preserve Spatial Info Mass Comparable to CDMS/Edelweiss Detector

CDMS IIUCSB July 26, 2002 ICHEP 31 - Harry Nelson keV Ar recoils 500 electron-ion pairs 15 keV  s 500 electron-ion pairs 13 keV e electron-ion pairs Nuclear Recoils  Discrimination by Imaging … Maybe even the direction of the recoil can be reconstructed

CDMS IIUCSB July 26, 2002 ICHEP 31 - Harry Nelson 25 Diurnal Variation (if WIMP `wind’)

CDMS IIUCSB July 26, 2002 ICHEP 31 - Harry Nelson 26 TPC operating nowCalibration Ionization Spatial Size Recoils Gammas Up Here Competitive sensitivity after a few months of running

CDMS IIUCSB July 26, 2002 ICHEP 31 - Harry Nelson 27 Lots of recent progress  Edelweiss  Zeplin-1  CDMS in a few months  DRIFT on line Everyone has expansion plans to keep gain orders of magnitude both in near and long term future 2010… let’s hope we have an LSP WIMP and are doing astrophysics with it and studying it in LHC decays! Summary

CDMS IIUCSB July 26, 2002 ICHEP 31 - Harry Nelson 28 CDMS collaboration, particularly Tarek Saab, Richard Schnee, Rick Gaitskell, Chris Savage, Ron Ferril Zeplin - Nigel Smith, Neil Spooner DRIFT - Dan Snowden-Ifft, Jeff Martoff Acknowledgements