cdms and supercdms - taup conferenceoverview suf, 10 mwe soudan, 2100 mwe snolab, 6000 mwe 1998 -...
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CDMS andSuperCDMS
Wolfgang RauQueen’s University Kingston
for the CDMS and SuperCDMS collaborations
CDMS/SuperCDMS Collaboration
California Institute of TechnologyZ. Ahmed, B. Doughthery, J . Filippini, S.R. Golwala, D. Moore, R. Nelson
Fermi National Accelerator LaboratoryD. A. Bauer, F. DeJongh, J. Hall, S. Hansen, D. Holmgren, L. Hsu, R.L. Schmitt, R.B. Thakur, J. Yoo
Massachusetts Institute of TechnologyA. Anderson, E. Figueroa-Feliciano, S. Hertel, S.W. Leman, K.A. McCarthy, P. Wikus
NISTK. Irwin
Queen’s UniversityC.H. Crewdson , P. Di Stefano , J. Fox , O. Kamaev,S. Liu , C. Martinez , P. Nadeau , K. Page , W. Rau, M.-A. Verdier. Y. Ricci
Santa Clara UniversityB. A. Young
SLAC/KIPACM. Asai, A. Borgland, D. Brandt, P. Brink,, W. Craddock, E. do Couto e Silva, G.G. Godrey, J. Hasi, M. Kelsey, C. J. Kenney, P. C. Kim, R. Partridge, R. Resch, D. Wright
Southern Methodist UniversityJ. Cooley, B. Karabuga, H. Qiu, S. Scorza
Stanford UniversityB. Cabrera, R. Moffatt, M. Pyle, M. Razeti, B. Shank, S. Yellin, J. Yen
Syracuse UniversityM. Kos, M. Kiveni, R. W. Schnee
Texas A&MR. Harris, A. Jastram, K. Koch, R. Mahapatra, M. Platt, K. Prasad, J. Sander
University of California, BerkeleyM. Daal, T. Doughty , N. Mirabolfathi, A. Phipps, B. Sadoulet,D. Seitz, B. Serfass, D. Speller, K.M. Sundqvist
University of California, Santa BarbaraR. Bunker, D.O. Caldwell, H. Nelson
University of Colorado DenverB.A. Hines, M.E. Huber
University of FloridaD. Balakishiyeva, T. Saab, B. Welliver
University of MinnesotaH. Chagani, J. Beaty, P. Cushman, S. Fallows, M. Fritts, T. Hoffer, V. Mandic, X. Qiu, R. Radpour, A. Reisetter, A. Villano, J . Zhang
University of ZurichS. Arrenberg, T. Bruch, L. Baudis, M. Tarka
2TAUP 2011, Munich - CDMS - W. Rau
Overview
SUF, 10 mwe
Soudan, 2100 mwe
SNOLAB, 6000 mwe
1998 - 2002 CDMS I6 detectors1 kg Ge (30 kgd )σ < 3.5e-42 cm2
2003 - 2009
CDMS II 30 detectors~4 kg Ge (300 kgd)σ < 3.5e-44 cm2
SuperCDMS @ Soudan15 detectors 10 kg Ge (~1200 kgd)σ < 5e-45 cm2
2014 - 2017
SuperCDMS @ SNOLAB 80-90 detectors100 kg Ge (~35000 kgd)σ < 3e-46 cm2
SuperCDMS test facility @ SNOLAB (2011)
exposures areafter all cuts!
2009 - 2013
3TAUP 2011, Munich - CDMS - W. RauAnalysis
ConclusionCDM
SO
verviewSuper
CDMS
AnalysisConclusion
CDMS
Overview
SuperCDM
SBeyond SuperCDMS
FundedPlanned
Memorandum of understanding signed between EURECA and GEODM/SuperCDMSfor exchange of information / collaboration in technical questions
Log(σ)[cm2] [pb]
- 43
- 44
- 45
- 46
- 47
- 7
- 8
- 9
- 10
- 11
19 Ge detectors, ~5 kgCDMS II, oZIP 1 cm x 3”, ~250 g
GEODM 6” x 2”~5000 g
hundreds of detectors, >1000 kg
O(100) detectors, 100 kg range
SuperCDMSSNOLAB, iZIP
3.3 cm x 10 cm ~1200 g
SuperCDMSSoudan, iZIP 15 detectors, ~10 kg1”x 3”, ~630 g
!!??
4TAUP 2011, Munich - CDMS - W. Rau
AnalysisConclusion
CDMS
Overview
SuperCDM
S
• Overview• CDMS Technology• Analysis and Results• SuperCDMS• Conclusions
Overview5TAUP 2011, Munich - CDMS - W. Rau
EvidenceAnalysis
ConclusionCDM
SO
verviewSuper
CDMS
CDMS TechnologyOperating Principle
Phonon energy [keV]
Ioni
zatio
n en
ergy
[keV
eeq]
Nuclear recoilsfrom neutrons
Electron recoilsfrom β’s and γ’s
Thermal couplingThermalbath
Phonon sensor
Target
+++ +
-- --
++
+ +
-- - - -
- -
++ +en
• Phonon signal: measures energy deposition
• Ionization signal: quenched for nuclear recoils (lower signal efficiency)
• Allows us to distinguish potential signal from background
Phon
on s
igna
lCh
arge
sign
al
Electron recoil Nuclear recoil
6TAUP 2011, Munich - CDMS - W. Rau
EvidenceAnalysis
ConclusionCDM
SO
verviewSuper
CDMS
CDMS TechnologyDetectors
Cryogenic ionization detectors, Ge (Si)
• ∅ = 7 cm, h = 1 cm, m = 250 g (100 g)• Thermal readout: superconducting phase
transition sensor (TES)• Transition temperature: 50 – 100 mK• 4 sensors/detector, fast signal (< ms)• Charge readout: Al electrode, divided
7TAUP 2011, Munich - CDMS - W. Rau
EvidenceAnalysis
ConclusionCDM
SO
verviewSuper
CDMS
CDMS TechnologyDetector Performance
Detector
Ioni
zatio
n/Re
coil e
nerg
y
Recoil energy [keV]
Collimator
++
+
+
––––+++
+
–– ––
β-band
γ-band
n-band
γs
neutrons
βs
Reduced charge signalbut faster phonon signal
surface event
nuclear recoil
rising edge slope
Z -sensitiveI onization andP honondetectors
8TAUP 2011, Munich - CDMS - W. Rau
Surface Effect
EvidenceAnalysis
ConclusionCDM
SO
verviewSuper
CDMS
CDMS at SoudanExperimental Setup
„Tower“(6 Detectors)
Cryostat, ColdboxShielding
SoudanUnderground lab(2000 m w.e.)
5 Towers (~ 5 kg Ge ) operated 2006 – 2008
9TAUP 2011, Munich - CDMS - W. Rau
EvidenceAnalysis
ConclusionCDM
SO
verviewSuper
CDMS
CDMS – Data AnalysisBackground Estimate – Neutrons
Radiogenic NeutronsFrom rock
negligible (neutron shield!)From experimental setup • estimated from screening
measurements, γ BG analysis• Main contributions from
spontaneous fission of U in Cu/Pb• Caveat: cannot measure U with γ
screening, only daughters –ICPMS measurement for EXO (Pbfrom same source) indicate lower contamination
• Total events expected (latest data set):0.03 – 0.06
Cosmogenic NeutronsMuons in experimental setup; internal
negligible (muon veto detector)Muons in surrounding rock; external• Use Monte Carlo to estimate rate• Compare MC for n from vetoed
(internal) muons to measured rate• Scale MC result for external muons
by ‘measured/MC’ ratio for internal muons
• Expected events (latest data set): 0.04 (stat) + 0.04
– 0.03
10TAUP 2011, Munich - CDMS - W. Rau
EvidenceAnalysis
ConclusionCDM
SO
verviewSuper
CDMS
CDMS – Data AnalysisBackground Estimate – Surface Events, ‘Leakage’
Timing Distribution – Surface vs. Neutrons
Surface events
from Bacalibration
Nuclear recoils from Cf neutron
source
Tail distribution different for each detector determines cut position
11TAUP 2011, Munich - CDMS - W. Rau
EvidenceAnalysis
ConclusionCDM
SO
verviewSuper
CDMS
CDMS – Data AnalysisBackground Estimate – Surface Events, ‘Leakage’
Estimate background from calibration data, single scatters outside NR band, multiple scatters inside and outside NR band
Calibration Data
12TAUP 2011, Munich - CDMS - W. Rau
EvidenceAnalysis
ConclusionCDM
SO
verviewSuper
CDMS
CDMS – Data AnalysisBackground Estimate – Surface Events, ‘Leakage’
Estimate background from calibration data, single scatters outside NR band, multiple scatters inside and outside NR band
Single Scatters
13TAUP 2011, Munich - CDMS - W. Rau
EvidenceAnalysis
ConclusionCDM
SO
verviewSuper
CDMS
CDMS – Data AnalysisBackground Estimate – Surface Events, ‘Leakage’
Overall estimated leakage (latest data set): 0.8 events
Estimate background from calibration data, single scatters outside NR band, multiple scatters inside and outside NR band
Multiple Scatters
13TAUP 2011, Munich - CDMS - W. Rau
EvidenceAnalysis
ConclusionCDM
SO
verviewSuper
CDMS
CDMS – Data AnalysisLikelihood analysis
• Determine how well the event distribution fits surface event hypothesis
• Compare to how well it fits nuclear recoil hypothesis
• Conclusion: either might be possible
Surface events
from Bacalibration
Nuclear recoils from Cf neutron
source
14TAUP 2011, Munich - CDMS - W. Rau
EvidenceAnalysis
ConclusionCDM
SO
verviewSuper
CDMS
ResultsSpin independent interaction
CDMS2010XENON100
EDELWEISS2009
CDMS2009
15TAUP 2011, Munich - CDMS - W. Rau
EvidenceAnalysis
ConclusionCDM
SO
verviewSuper
CDMS
ResultsCDMS – EDELWEISS: Combined Analysis
16TAUP 2011, Munich - CDMS - W. Rau
EvidenceAnalysis
ConclusionCDM
SO
verviewSuper
CDMS
ResultsSpin independent interaction
CDMS2010
EDELWEISS II
XENON100 – 100d
CDMS + EDELWEISS
17TAUP 2011, Munich - CDMS - W. Rau
EvidenceAnalysis
ConclusionCDM
SO
verviewSuper
CDMS
DAMA/CoGeNT – Low Mass WIMPs?
Evidence:• DAMA: annual oscillation signal• CoGeNT: Exponential rate increase
at low energy• Both have an interpretation as low
mass WIMP (< 10 GeV) signal
What can we (CDMS) do?• Lower Threshold• Background increases• BUT: expected rate shoots up
dramatically
WIMP Recoil Spectrum
18TAUP 2011, Munich - CDMS - W. Rau
EvidenceAnalysis
ConclusionCDM
SO
verviewSuper
CDMS
DAMA/CoGeNT – Low Mass WIMPs?
Evidence:• DAMA: annual oscillation signal• CoGeNT: Exponential rate increase
at low energy• Both have an interpretation as low
mass WIMP (< 10 GeV) signal
What can we (CDMS) do?• Lower Threshold• Background increases• BUT: expected rate shoots up
dramatically
WIMP Recoil Spectrum
18TAUP 2011, Munich - CDMS - W. Rau
EvidenceAnalysis
ConclusionCDM
SO
verviewSuper
CDMS
CDMS – Low Threshold AnalysisSUF and Soudan
• Low mass WIMPs deposit little energy
• Study data below discrimination threshold
• Significant background: understood, but not subtracted
• Competitive sensitivity• Stanford Underground Facility:
early run (2001/02): very low noise, low trigger threshold (sub keV)
• Soudan: lower background, but slightly higher threshold (2 keV)
• New method of finding limit for multiple detectors with different background performance (Yellin)
Stanford Data
Soudan Data
19TAUP 2011, Munich - CDMS - W. Rau
EvidenceAnalysis
ConclusionCDM
SO
verviewSuper
CDMS
ResultsLow mass WIMPs
DAMA
CoGeNT
CDMS10 keV
CDMS, SUF
CDMSSoudan
20TAUP 2011, Munich - CDMS - W. Rau
EvidenceAnalysis
ConclusionCDM
SO
verviewSuper
CDMS
ResultsLow mass WIMPs
DAMA
CoGeNT
CDMS10 keV
CDMS, SUF
CDMSSoudan
XENON 100
XENON 100, 10d, Likelyhood analysis
20TAUP 2011, Munich - CDMS - W. Rau
EvidenceAnalysis
ConclusionCDM
SO
verviewSuper
CDMS
SuperCDMSSoudan
• Larger mass per module: ~240 g → ~600 g
• Increased thickness → improved bulk/surface ratio
• Improved sensor design for better event reconstruction / surface event rejection
21TAUP 2011, Munich - CDMS - W. Rau
Phonon sensors on top and bottom
EvidenceAnalysis
ConclusionCDM
SO
verviewSuper
CDMS
SuperCDMSSoudan
• Larger mass per module: ~240 g → ~600 g
• Increased thickness → improved bulk/surface ratio
• Improved sensor design for better event reconstruction / surface event rejection
Basic configuration
+2 V 0 V
-2 V 0 V
ZIP with interleaved electrodes: iZIP
Electric field calculationSurface events
21TAUP 2011, Munich - CDMS - W. Rau
EvidenceAnalysis
ConclusionCDM
SO
verviewSuper
CDMS
SuperCDMSSoudan
• Larger mass per module: ~240 g → ~600 g
• Increased thickness → improved bulk/surface ratio
• Improved sensor design for better event reconstruction / surface event rejection
• New detectors tested underground• DAQ adjusted to new requirements• Increase total target mass (~10 kg)• Start next dark matter run in October
operate 2-3 years• Improve sensitivity by ~ x5-8• Expect limitation from cosmogenic
background
Basic configuration
+2 V 0 V
-2 V 0 V
ZIP with interleaved electrodes: iZIP
Electric field calculation
21TAUP 2011, Munich - CDMS - W. Rau
EvidenceAnalysis
ConclusionCDM
SO
verviewSuper
CDMS
SuperCDMSSNOLAB - Setup
SuperCDMS Setup at SNOLAB (planned)• Detector volume holds ~ 150 kg of active
target• Pb/Cu shielding against external radiation• Increased PE shielding against neutrons• Consider to incorporate neutron detector
into shield (not shown)Shileding [mwe]
log (
Muo
n flu
x [m
-2s-1
])
CryostatShielding
Cross section
DetectorVolume
Move to SNOLAB• Less Cosmic radiation• Cleaner environment• Good Lab
infrastructure
22TAUP 2011, Munich - CDMS - W. Rau
EvidenceAnalysis
ConclusionCDM
SO
verviewSuper
CDMS
SuperCDMS – Detector Test FacilityUnderground at SNOLAB
Cryo
stat
Wat
er
shie
ld
Sketch of Underground detector Testing Facility at SNOLAB
• Discrimination power required for 100 kg scale (or larger) experiments cannot be tested above ground (accidental neutron interaction rate too high)
• Detector modules larger than present SuperCDMS detectors are desirable but may not be testable above ground (pile-up)
• Background from contamination of detectors cannot be measured above groundSUF cryostat being upgraded; system test late 2011; commissioning early 2012
Motivation
Mostly neutron background
Recoil energy [keV]
Ioni
zatio
n yi
eld
23TAUP 2011, Munich - CDMS - W. Rau
AnalysisConclusion
CDMS
SuperCDM
SO
verview
Conclusion
• CDMS uses cryogenic semiconductor detector to search for WIMP interactions
• CDMS has provided best sensitivities for most of the past decade and continues to be among the top players
• So far no evidence for WIMPs has been found• Low Threshold Analysis in tension with low-mass WIMP interpretation of
DAMA and CoGeNT• SuperCDMS at Soudan (~10 kg, iZIP detectors) about to start• Will be limited by cosmogenic background after 2-3 years• Planning 100-150 kg setup for SNOLAB• Underground test facility under construction; commissioning in 2012
24TAUP 2011, Munich - CDMS - W. Rau
EvidenceConclusion
Super-heated
CryogenicDirectional
Scintillator
Fine
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