Constraints on Low-Mass WIMP Signals from CDMS Steven W. Leman (MIT) 18 March 2011 Rencontres de Moriond EW La Thuile, Valle d Aosta, Italy
CDMS Members California Institute of Technology Z. Ahmed, J. Filippini, S.R. Golwala, D. Moore, R. Nelson, R.W. Ogburn Case Western Reserve University D. Akerib, C.N. Bailey, M.R. Dragowsky, D.R. Grant, R. Hennings-Yeomans Fermi National Accelerator Laboratory D. A. Bauer, F. DeJongh, J. Hall, D. Holmgren, L. Hsu, E. Ramberg, R. B. Thakur, R.L. Schmitt, J. Yoo Massachusetts Institute of Technology A. Anderson, E. Figueroa-Feliciano, S. Hertel, S.W. Leman, K.A. McCarthy, P. Wikus NIST K. Irwin Queen s University P. Di Stefano, C. Crewdson, J. Fox, O. Kamaev, S. Liu, C. Martinez, P. Nadeau, W. Rau, Y. Ricci, M. Verdier Santa Clara University B. A. Young Southern Methodist University J. Cooley, B. Karabuga, S. Scorza, H. Qiu SLAC/KIPAC M. Asai, A. Borgland, D. Brandt, P.L. Brink, W. Craddock, E. do Couto e Silva, G.G. Godfrey, J. Hasi, M. Kelsey, C. J. Kenney, P. C. Kim, R. Partridge, R. Resch, D. Wright Stanford University B. Cabrera, M. Cherry, R. Moffatt, L. Novak, M. Pyle, M. Razeti, B. Shank, A. Tomada, S. Yellin, J. Yen Syracuse University M. Kos, M. Kiveni, R. W. Schnee Texas A&M A. Jastram, K. Koch, R. Mahapatra, M. Platt, K. Prasad, J. Sander University of California, Berkeley M. Daal, T. Doughty, N. Mirabolfathi, A. Phipps, B. Sadoulet, D. Seitz, B. Serfass, D. Speller, K.M. Sundqvist University of California, Santa Barbara R. Bunker, D.O. Caldwell, H. Nelson University of Colorado Denver B.A. Hines, M.E. Huber University of Florida T. Saab, D. Balakishiyeva, B. Welliver University of Minnesota J. Beaty, H. Chagani, P. Cushman, S. Fallows, M. Fritts, V. Mandic, X. Qiu, A. Reisetter, J. Zhang University of Zurich S. Arrenberg, T. Bruch, L. Baudis, M. Tarka
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CDMS The Cryogenic Dark Matter Search
Event Discrimination DAMA, ZEPLIN I CLEAN, KIMS Scintillation XENON, LUX WARP, ArDM ZEPLIN II & III CRESST ROSEBUD Phase Transition Ionization CoGeNT, SIMPLE TEXONO CDMS Edelweiss Phonons (heat) CRESST I PICASSO COUPP
Instrumentation Al fins absorb phonons 2 Ionization Channels 4 Phonon Channels Transition Edge Sensors 7.6 cm 1 or 2.5 cm
Carrier Transient Carriers (bulk events) go the right way Carriers (surface events) injected into the wrong electrode γ e - phonons h + + ballistic phonons γ -3V
CDMS Low Energy Analyses Stanford Underground Facility Soudan
DAMA and CoGeNT annual modulation Aalseth et al., arxiv:1002.4703 WIMP-like exponential spectra Bernabei et al., Eur. Phys. J. C 56 333 (2008), arxiv:0804.2741
WIMP Event Rates 1 10-41 cm 2 cross section 544 km s -1 escape velocity 0.3 GeV cm -3 density Event rate (kg 1 kev 1 d 1 ) 10 0 10 1 10 2 10 2 10 4 10 6 5 GeV c -2 100 GeV c -2 0.1 1 10 100 Recoil energy (kev) Ge Si
Stanford Result Akerib et al, PRD 82, 122004 (2010) Shallow site (17 m water equivalent overburden) 118 live days from Dec 2001 - June 2002 4 224 g Ge 1 Ge not used due to high analysis threshold 1 Ge sensitive to cryostat temperature, live time reduced 2 105 g Si
Cuts Data Quality (No energy dependence, 99% efficiency) Noise 1 Pileup Chi2 0.5 Phonon and ionization pretrigger 0 < 5 σ from mean Single scatter (100% efficiency) no Muon veto, 50-80 µs (67-78% efficiency) Inner electrode (83% eff) Nuclear recoil (93-96% eff) Threshold efficiency Cut efficiency 0.6 0.5 Z6 (Si) Z2 (Ge) 0.5 1 10 100 Recoil energy (kev) mean lower limit
Energy Calibration Cosmic ray activated Z3 (Ge) (Ge68) and neutron activated (Ge71) lines at 1.3 and 10.4 kev Cosmogenic (Ge73m) at 66.7 kev Event rate (kg 1 kev 1 d 1 ) 100 10 1 0.5 1 10 100 Recoil energy (kev) [Y corrected] ER
WIMP Candidates cut and threshold adjusted event rate cut adjusted event rate raw event rate Event rate (kg 1 kev 1 d 1 ) 10 Ge 1 0.1 0.01 10 1 0.1 0.01 0.5 1 10 Recoil energy (kev) 100 Si
Ionization vs. Energy Ge Si Total 1080 970 Event Accounting (%) 1.3 kev line 32 0 Zero-charge 30-40 30-40 14C betas 0 40 Compton 10-20 10-20 Cosmogenic 6 2 Other 2-22 0-18 Ionization yield Ionization yield 1 0.5 0 1 0.5 0 Z5 (Ge) Z4 (Si) Zero Ionization Events Electron Capture Lines Nuclear Recoils Electron Recoils 0.5 1 10 100 Recoil energy (kev)
Ionization vs. Energy Ge Si Total 1080 970 Event Accounting (%) 1.3 kev line 32 0 Ionization yield 1 0.5 Z5 (Ge) Electron Capture Lines Known events NOT 0 subtracted 1 Zero-charge 30-40 30-40 14C betas 0 40 Compton 10-20 10-20 Cosmogenic 6 2 Other 2-22 0-18 Ionization yield 0.5 0 Z4 (Si) Zero Ionization Events Nuclear Recoils Electron Recoils 0.5 1 10 100 Recoil energy (kev)
WIMP nucleon cross section (cm 2 ) 10 38 10 39 10 40 10 41 WIMP-Nucleon 90% Exclusion Limits 2 4 6 8 10 100 WIMP mass (GeV/c 2 ) DAMA / LIBRA Si only Ge Si + Ge (500 km s -1 ) DAMA / LIBRA + CoGeNT (600 km s -1 ) XENON100 (scintillation eff.) WIMP nucleon cross section (cm 2 ) constant decreasing - CoGent + CRESST - 10 38 10 39 10 40 10 41 2 4 6 8 10 100 WIMP mass (GeV/c 2 ) C. Savage, et al, J. Cosmol. Astropart. Phys. 04 (2009) 010 C. Savage, et al, J. Cosmol. Astropart. Phys. 09 (2009) 036 C. Savage, et al, arxiv:1006.0972 D. Hooper et al., Phys. Rev. D 82, 123509 (2010) A. Bottino, et al, Phys. Rev. D 67, 063519 (2003) A. Bottino, et al, ibid.68, 043506 (2003); 69, 037302 (2004) G. Belanger, et al, J. High Energy Phys. 03 (2004) 012
Soudan Result Ahmed et al, PRL (accepted), arxiv:1011.2482 Oct 2006 - Sept 2008 241 kg days 8 230 g Ge with lowest-detector thresholds of 2 kev NR band (+1.25, 0.5)σ Maximizes sensitivity to nuclear recoils while minimizing expected backgrounds
Ionization vs. Energy 1.3 kev line 9-1.:;<.-104.+/= "#) "#( "#' "#& "#% "#$ "#! " "#! $ Sidebands for background estimate: Compton Surface 2! zero charge band Zero-charge!"!"" *+,-./0+1+234056+78 Event rate (kev 1 kg 1 day 1 ) 10 0 10 1 10 2 Acceptance 0.5 0.25 0 0 2 4 6 8 10 Recoil energy (kev) 2 5 10 15 20 Recoil energy (kev) Total Zero-charge Surface Bulk 1.3 kev
Ionization vs. Energy 1.3 kev line 9-1.:;<.-104.+/= "#) "#( "#' Compton 10 2 "#& Known events NOT subtracted "#% "#$ "#! " "#! $ Sidebands for background estimate: Surface 2! zero charge band Zero-charge!"!"" *+,-./0+1+234056+78 Event rate (kev 1 kg 1 day 1 ) 10 0 10 1 Acceptance 0.5 0.25 0 0 2 4 6 8 Recoil energy (kev) 2 5 10 15 20 Recoil energy (kev) Total Zero-charge Bulk Surface 1.3 kev 10
CDMS and CoGeNT &! & Efficiency Corrected Spectra - Both use Ge detectors Signal in CoGeNT not seen in CDMS 6*7.89-23(4 & -30 & -:;1 & 5 &!! &! & 7 GeV c -2 90% confidence &! " 6*<(=> 6?@ABB-2;,,-:(85 6?@ABB-2C(98-:(85 -! " # $ '()*+,-(.(/01-23(45 % &! 7 GeV c -2 90% confidence Hooper et al., Phys. Rev. D 82, 123509 (2010), arxiv:1007.1005
WIMP-Nucleon 90% Exclusion Limits CDMS Stanford 1 kev -- CDMS Soudan 2 kev CDMS Soudan 10 kev - XENON100 + DAMA / LIBRA CoGeNT DAMA + CoGeNT CDMS Soudan 10 kev - CRESST -- XENON10 WIMP nucleon SI (cm 2 ) WIMP neutron SD (cm 2 ) 10 39 10 40 10 33 10 34 10 35 10 36 WIMP mass (GeV/c 2 ) 10 37 4 6 8 10 12 WIMP mass (GeV/c 2 )
SuperCDMS Interleaved Detectors
Microstrip Gas Chamber A. Oed 1988 NIM A 263 (1988) 351-359
SCDMS izip Detectors MSGC concept extended to CdZnTe, P. Luke Appl. Phys. Lett. 65 (22) 1994 SCDMS, P. Brink et al NIM A 559 (2006) 414-416
SCDMS izip Detectors
Surface Discrimination 1:10 4 surface Surface γ + e - discrimination from ionization signal Bulk γ Surface γ + e -
Log 10 (Muon Flux) (m -2 s -1 ) Future Limits Depth (meters water equivalent)
Backup Slides
Inner Charge Cut Area_qi = 83% Cf-252 passage = 81-83% Energy dependence 84% (4 kev) - 79% (100 kev) <4 kev, qi and qo indistinguishable, linearly extrapolate to 100% passage
Search Complementarity Direct bulk focus point Production coannihilation bulk Indirect coannihilation Higgs funnel