Gaitskell CDMS I + II + CryoArray Status Direct Detection of SUSY Cold Dark Matter Rick Gaitskell Brown University, Department of Physics see information at

CDMS Dark Matter - NY - May 2003 Rick Gaitskell CDMS Collaboration Santa Clara University B.A. Young Stanford University L. Baudis, P.L. Brink, B. Cabrera, C. Chang, T. Saab University of California, Berkeley V. Mandic, P. Meunier, N. Mirabolfathi, W. Rau, B. Sadoulet, A. Lu University of California, Santa Barbara D.A. Bauer, R. Bunker, D.O. Caldwell, R. Ferril, R. Mahapatra, H. Nelson, J. Sander, C. Savage, S. Yellin University of Colorado at Denver M. E. Huber University of Minnesota P. Cushman, L. Duong, A. Reisetter Brown University R.J. Gaitskell, J.-P. Thompson, M. J. Attisha, L de Viveiros Case Western Reserve University D.S. Akerib, D. Driscoll, S. Kamat, T.A. Perera, R.W. Schnee, G.Wang Fermi National Accelerator Laboratory M.B. Crisler, R. Dixon, D. Holmgren Lawrence Berkeley National Laboratory J.H Emes, R.R. Ross, A. Smith National Institute of Standards and Technology J. Martinis Princeton University T. Shutt

CDMS Dark Matter - NY - May 2003 Rick Gaitskell STATUS: CDMS II - Cold & Running “First Dark” achieved 12 detectors - cold & checked SOUDAN  6 Ge+6 Si  Cryo / DAQ / Electronics / Analysis operating Tower 1 - currently  calib  Prev. 1/2 Stanford - b/g well understood 120 live days (50 kg-days Ge) Tower not changed -> Soudan Will be some improvement at depth — Need stats to study bg (Prelim looks good) Tower 2  All New detectors Some improvements made in b/g handling Not yet measured b/g for this tower Initial SOUDAN  Similar run to Stanford: 50 Ge kg-days  Looking for Zero background (ZBG) >10 keV Expect very clean analysis Tower 1 Previously 1/2 year Stanford Tower 2 (New dets)

CDMS Dark Matter - NY - May 2003 Rick Gaitskell Direct Detection: History & Future Oroville (88) [m = ?? GeV - if significantly better limit obtained at different mass] 90% CL Limit on Cross section for 60 GeV WIMP (scalar coupling) ~1 event kg -1 day -1 ~1 event kg -1 yr -1 ~1 event 100 kg -1 yr -1 LHC Not meant to be a complete list - see Different Colours Indicate Different Technologies NOW rjg [m=20 GeV] Homestake (87) H-M (94) H’berg-Moscow (98), IGEX (00) DAMA (96) UKDMC (96) [m=100 GeV] DAMA (98) DAMA (00) Gaitskell (astroph ) CDMS SUF (99) CDMS SUF (02) Edelweiss (98) Edelweiss (01) ZEPLIN I Xe (02) Edelweiss (02) DRIFT II 1 kg CS 2 (T) ZEPLIN II+III 10 kg Xe (T) XENON / ZEPLIN 1t Xe (T) CDMS Soudan (T) 7 kg Ge+Si Cryodet Majorana Phase 1 (T) GENINO (T) 100 kg Ge Diode GENIUS (T) 100 kg Ge Diode CryoArray (T) tonne Cryodet DRIFT III 100 kg CS 2 (T) Ge NaI Cryodet (T) Target Signal Liq Xe Gas CS 2

CDMS Dark Matter - NY - May 2003 Rick Gaitskell Latest & Greatest Limits on Scalar C-S for WIMPs Latest Edelweiss result (updated May 2003) ZEPLIN I result (announced Sept 2002) CDMS I result (updated June 2003) ZEPLIN I - Liq nat130 Xe Edelweiss - nat72 Ge CDMS I Final ~1 event kg -1 day -1

CDMS Dark Matter - NY - May 2003 Rick Gaitskell Detectors provide near-perfect event-by-event discrimination against otherwise dominant electron-recoil backgrounds 616 Neutrons (external source) 1334 Photons (external source) CDMS Background Discrimination Explanation of basics (…On-going improvements in rejection) Ionization Yield (ionization energy per unit recoil energy) depends strongly on type of recoil Most background sources (photons, electrons, alphas) produce electron recoils WIMPs (and neutrons) produce nuclear recoils Ionization Threshold 233 Electrons (tagged contamination) Particles (electrons) that interact in surface “dead layer” of detector result in reduced ionization yield, very good (>95%) against surface electron-recoil backgrounds bulk > 1 / 2 year’s background >> 1 / 2 year’s signal !! NOT A SIMULATION! >98%

CDMS Dark Matter - NY - May 2003 Rick Gaitskell CDMS II - Calibrations at Stanford ZIP Detector (250g Ge, or 100 g Si)  20,400 gamma events (5-100 keV) ~ 1 week continuous calibration with 60 Co source  = ~one count in 12 years of gamma background (assuming project background level of 0.25 counts/keV/kg/day at CDMSII Soudan. Calibration still Poisson stats/neutron background limited )  Sensitivity better than 1 WIMP per year per detector Neutrons (external source) Gammas (external source) Trigger Threshold 1334 gamma events, 616 neutron events rjg

CDMS Dark Matter - NY - May 2003 Rick Gaitskell 380  m Al fins 60  m wide Photolithographic patterning like CMOS but 1 big chip 37 cells per quadrant 7x4 array of W transition-edge sensors per cell, with Al “collector” fins covering only fraction of surface ZIP Detector Phonon Sensor Close-up A B C D

CDMS Dark Matter - NY - May 2003 Rick Gaitskell Am 241 :  14, 18, 20, 26, 60 kev Cd Al foil :  22 kev Demonstration of xyZIP Position Sensitivity Cd 109 :  22 kev i.c. electr 63, 84 KeV Delay Plot AD CB

CDMS Dark Matter - NY - May 2003 Rick Gaitskell Working at Soudan

CDMS Dark Matter - NY - May 2003 Rick Gaitskell STATUS: CDMS II - Cold & Running “First Dark” achieved 12 detectors - cold & checked SOUDAN  6 Ge+6 Si  Cryo / DAQ / Electronics / Analysis operating Tower 1 - currently  calib  Prev. 1/2 Stanford - b/g well understood 120 live days (50 kg-days Ge) Tower not changed -> Soudan Will be some improvement at depth — Need stats to study bg (Prelim looks good) Tower 2  All New detectors Some improvements made in b/g handling Not yet measured b/g for this tower Initial SOUDAN  Similar run to Stanford: 50 Ge kg-days  Looking for Zero background (ZBG) >10 keV Expect very clean analysis Tower 1 Previously 1/2 year Stanford Tower 2 (New dets)

CDMS Dark Matter - NY - May 2003 Rick Gaitskell STATUS: CDMS II - Cold & Running “First Dark” achieved 12 detectors - cold & checked out  6 Ge+6 Si  Cryo / DAQ / Electronics / Analysis operating Tower 1 - currently  calib  Prev. 1/2 Stanford - b/g well understood 120 live days (50 kg-days Ge) Tower not changed -> Soudan Will be some improvement at depth — Need stats to study bg (Prelim looks good) Tower 2  All New detectors Some improvements made in b/g handling Not yet measured b/g for this tower Initial Goal  Similar run to Stanford: 50 Ge kg-days  Looking for Zero background (ZBG) >10 keV Expect very clean analysis Tower 1 1/2 year Stanford Tower 2 (New dets)

CDMS Dark Matter - NY - May 2003 Rick Gaitskell 1 per minute in 4 m 2 shield Depth (mwe) Log 10 (Muon Flux) (m -2 s -1 ) Stanford Underground Facility 500 Hz muons in 4 m 2 shield Expected Backgrounds for CDMS II at Soudan On track for events/kg/keV/day at 15 keV? Depth of 2000 mwe reduces neutron background from ~1 / kg / day to ~1 / kg / year Also better neutron shielding

CDMS Dark Matter - NY - May 2003 Rick Gaitskell 1999 Ge BLIP Ge Ga peak from 71 Ge: decays Expected Backgrounds for CDMS II at Soudan On track for events/kg/keV/day at 15 keV? Depth of 2000 mwe reduces neutron background from ~1 / kg / day to ~1 / kg / year Also better neutron shielding Photon background is already 0.7 events /(kg keV day) x expected leakage, despite the shallow site (good enough with background subtraction)

CDMS Dark Matter - NY - May 2003 Rick Gaitskell BLIP5 single Z1+Z2+Z3 Ge electrons single Expected Backgrounds for CDMS II at Soudan On track for events/kg/keV/day at 15 keV? Depth of 2000 mwe reduces neutron background from ~1 / kg / day to ~1 / kg / year Also better neutron shielding Photon background is already 0.7 events /(kg keV day) x <10 -3 expected leakage, despite the shallow test site Electron background is 0.1 events /(kg keV day) x ~0.04 expected leakage, despite the shallow site (need ~2x improvement from depth, or improvement from depth, or better surface screening/cleaning)

CDMS Dark Matter - NY - May 2003 Rick Gaitskell Latest & Greatest Limits on Scalar C-S for WIMPs CDMS II Initial goal 20x improvement over CDMS I ZeroBG 50 kg-days Ge ZEPLIN I - Liq nat130 Xe Edelweiss - nat72 Ge CDMS I Final ~1 event kg -1 day -1 Initial Goal 2003 CDMS II 20x ZBG 50 kg-days

CDMS Dark Matter - NY - May 2003 Rick Gaitskell CDMS I ( )  SI upper limits now eclipsed by EDELWEISS, Zeplin I except at low WIMP mass.  CDMS data are incompatible with DAMA signal for standard WIMPs & halo.  Sensitivity limited by neutrons from muons interacting in surrounding rock. CDMS II ( )  12 detectors (1.5 kg Ge, 0.6 kg Si) Soudan Stanford discrimination tests of 6 dets exceeded performance expectations. Stanford b/g testing showed expected reduction of neutron background by factor of ~2.3 due to installation of internal moderator (agreement with MC predictions.)  “First Dark” achieved Apr Initial Goal ~50 kg-days Ge (similar to previous Stanford, but no neutrons!) CryoArray ( or so…)  Sensitivity to study WIMP physics down to s~ cm 2 (many events if higher s   Modest improvements over current results (shared): Discrimination:  already good enough,  within factor few. Backgrounds: x20 reductions vs CDMS II, 2-3x vs best current IGEX, H-M R. Abusaidi et al., Phys. Rev. Lett. 84, 5699 (2000). D.Abrams et al., Phys. Rev. D astro-ph/ v3 D.Akerib et al. Phys. Rev Lett. hep-ex/ Final Stanford Analysis CDMS Conclusions

Gaitskell Backup Slides Q&A (Not Used in Talk)

CDMS Dark Matter - NY - May 2003 Rick Gaitskell 10.6 m earth Detectors Inner Pb shield Polyethylene Pb Shield Active Muon Veto Fridge Old CDMS Location: Stanford Shallow Site Expect neutron background ~2 / kg / day produced outside shield; measure using  Two materials (Si more sensitive to neutrons, Ge more sensitive to WIMPs)  Multiple-detector neutron scatters Copper Shielded, low-background environment Shallow (17 mwe rock)  Hadronic cosmic-ray flux reduced by >1000x  Muons reduced by ~5x Active muon veto  >99.9% efficient  Reject ~100 neutrons per kg-day produced by muons within shield   n n n..

CDMS Dark Matter - NY - May 2003 Rick Gaitskell CryoArray: A 3 rd Generation Experiment Based on extrapolation of CDMS technology/strategy Basic parameters/goals  1000 kg x 2 (live) years  ~100 WIMPs at cm 2 ~10 WIMPs at cm 2  ~10’s background events Excellent discrimination so need little background reduction  Internal ( ,  ) and external (n) Main challenge:  Increase mass (~100x) and manufacturability of detectors/cryo package  Maintain Performance Possible sites  Soudan (CDMS II) among shallower sites (n background problematic)  National Underground Facility Depth Shared resources (vetos, assembly, materials screening, fabrication???) 10 4 – 10 5 increase over present limits 10 2 – 10 3 increase over expts under construction

CDMS Dark Matter - NY - May 2003 Rick Gaitskell Photon background is very manageable  Current lower limit on discrimination already good enough if raw rate reduced to 13 mdru, ~2-3 times better than best levels reached so far (by IGEX, H-M) achieve via materials selection and simplification of structures (little mounting material)  Screening to g/g can reveal contamination source of such a background Electron background more worrisome, but certainly tractable  Need to screen & clean surfaces to 2.5 x counts/ (keV m 2 day), or to 10x better if rejection remains only 95% -- novel but appears to be doable Background Projections - CryoArray (1 ton) dru = 1 event keV -1 kg -1 day -1 see Schnee, Gaitskell & Akerib astro-ph/ Energy Range keV

CDMS Dark Matter - NY - May 2003 Rick Gaitskell “First Dark” at Soudan Mine, Minnesota in Apr 2003 Soudan Mine ZIP 1 (Ge) ZIP 2 (Si) ZIP 3 (Ge) ZIP 4 (Si) ZIP 5 (Ge) ZIP 6 (Si) SQUID cards FET cards 4 K 0.6 K 0.06 K 0.02 K First tower with 4 Ge and 2 Si ZIPs (NOW TWO TOWERS)

CDMS Dark Matter - NY - May 2003 Rick Gaitskell ZIP 1 (Ge) ZIP 2 (Ge) ZIP 3 (Ge) ZIP 4 (Si) ZIP 5 (Ge) ZIP 6 (Si) SQUID cards FET cards 4 K 0.6 K 0.06 K 0.02 K CDMS II Data Run Adopted advanced, “ZIP” detector technology  Simultaneous measurement of ionization and athermal phonon signal. 4 phonon channels yield xy position of interaction Pulse risetime allows rejection of surface events Tested understanding of neutron background  Added inner polyethylene predicted to lower neutron background by ~2.3x  Measured n background in Si & Ge at once Tested first tower of detectors for Soudan.  4 Ge and 2 Si ZIPs November ‘01 to June ‘02.  67 livedays at 3 V bias = 28 kg days after cuts.  52 livedays at 6 V bias = 22 kg days after cuts.  Acceptable contamination levels.  Photon rejection better than proposal.

CDMS Dark Matter - NY - May 2003 Rick Gaitskell Photon Rejection with ZIPs Histogram of ionization yield for different energy ranges for in- situ photon calibration at Stanford Underground Facility No events leaked into the nuclear-recoil acceptance region in detector Z5  Photon rejection > 99.99% (0/26610) for keV range Equivalent to 5 years of background operation at 0.8 events/keV/kg/day  Photon rejection > 99.9% (0/3863) for 5-20 keV range 5x better performance than specified in CDMS II proposal  Other detectors display similar performance with only a few events out of ~ leaking into the nuclear-recoil acceptance region Photon Calibration

CDMS Dark Matter - NY - May 2003 Rick Gaitskell SUF 21 - Background Data Plots for background data from the current run –Muon Anti-Coincident Data –Risetime cut & Single-Scatter cut & fiducial-volume cuts –Cuts set with low-background data “blinded” –About 45% efficiency for WIMPs –Only a few low-yield events remain

CDMS Dark Matter - NY - May 2003 Rick Gaitskell CDMS II at Soudan

CDMS Dark Matter - NY - May 2003 Rick Gaitskell Projected CDMS Sensitivity Limit from CDMS 1999 Ge BLIP run at Stanford Edelweiss Exclusion Limit SUSY g  -2 Baltz&Gondolo, PRL 86 (2001) 5004 No SUSY g  -2 Baltz&Gondolo, PRL 86 (2001) 5004 CMSSM Ellis et al. (2001) PRD 63, Projected sensitivity for a 1-ton CryoArray (~ 1 event / (100 kg yr) For more limit curves, see Gaitskell &Mandichttp://dmtools.berkeley.edu Large region allowed by SUSY theories shrinks to light-blue region if SUSY causes excess value of muon anomalous magnetic moment (g  -2) Projected sensitivity for CDMS at Soudan, with 5 towers 4 kg Ge, 1.5 kg Si: 0.1 events/kg/keV/year (100x better than present limit at Stanford).