CDMS and SuperCDMS - TAUP ConferenceOverview SUF, 10 mwe Soudan, 2100 mwe SNOLAB, 6000 mwe 1998 - 2002 CDMS I 6 detectors 1 kg Ge (30 kgd ) σ< 3.5e-42 cm 2 2003 - 2009 CDMS II 30

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

!!??


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


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


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


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


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


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


EvidenceAnalysis

ConclusionCDM

SO

verviewSuper

CDMS


Estimate background from calibration data, single scatters outside NR band, multiple scatters inside and outside NR band

Calibration Data


EvidenceAnalysis

ConclusionCDM

SO

verviewSuper

CDMS



Single Scatters


EvidenceAnalysis

ConclusionCDM

SO

verviewSuper

CDMS


Overall estimated leakage (latest data set): 0.8 events


Multiple Scatters


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


EvidenceAnalysis

ConclusionCDM

SO

verviewSuper

CDMS

ResultsSpin independent interaction

CDMS2010XENON100

EDELWEISS2009

CDMS2009


EvidenceAnalysis

ConclusionCDM

SO

verviewSuper

CDMS

ResultsCDMS – EDELWEISS: Combined Analysis


EvidenceAnalysis

ConclusionCDM

SO

verviewSuper

CDMS

ResultsSpin independent interaction

CDMS2010

EDELWEISS II

XENON100 – 100d

CDMS + EDELWEISS


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


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


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


EvidenceAnalysis

ConclusionCDM

SO

verviewSuper

CDMS

ResultsLow mass WIMPs

DAMA

CoGeNT

CDMS10 keV

CDMS, SUF

CDMSSoudan


EvidenceAnalysis

ConclusionCDM

SO

verviewSuper

CDMS

ResultsLow mass WIMPs

DAMA

CoGeNT

CDMS10 keV

CDMS, SUF

CDMSSoudan

XENON 100

XENON 100, 10d, Likelyhood analysis


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


Phonon sensors on top and bottom

EvidenceAnalysis

ConclusionCDM

SO

verviewSuper

CDMS

SuperCDMSSoudan




Basic configuration

+2 V 0 V

-2 V 0 V

ZIP with interleaved electrodes: iZIP

Electric field calculationSurface events


EvidenceAnalysis

ConclusionCDM

SO

verviewSuper

CDMS

SuperCDMSSoudan




• 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


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


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


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


EvidenceConclusion

Super-heated

CryogenicDirectional

Scintillator

Fine

Documents

CDMS and SuperCDMS - TAUP ConferenceOverview SUF, 10 mwe Soudan, 2100 mwe SNOLAB, 6000 mwe 1998 - 2002 CDMS I 6 detectors 1 kg Ge (30 kgd ) σ< 3.5e-42 cm 2 2003 - 2009 CDMS II 30