Pushing the Limits: Dark Matter Search with SuperCDMS · Dark Matter. Conclusion •Strong observational evidence for the existence of dark matter •WIMPs are probably the best motivated

Pushing the Limits: Dark Matter Search with

SuperCDMS

Wolfgang Rau Queen’s University Kingston

For the SuperCDMS Collaboration

Rubin Radius

Velo

city

Expected (Kepler)

Observed

Zwicky

Dark Matter

Dark Energy (>70 %)

Dark Matter (~23 %)

Luminous Matter (< 1 %)

Ordinary Matter (~ 4 %)

CMB

Predicted by SUSY: Neutralino Universal extra dimensions: Kaluza-Klein particles

WIMP

Here, but not yet observed in nature: Weakly interacting

Large scale structure of the Universe:

Slowly moving (‘cold’)

Not observed in accelerator experiments:

Massive

(Weakly Interacting Massive Particle)

Dark Matter

• Dark Matter Detection • CDMS Technology • CDMS Results • SuperCDMS • Conclusions

Overview 4 W. Rau – SuperCDMS at SNOLAB May 2012

Results Conclusion

CDMS

Dark Matter

Super CDM

S Dark Matter Detection

Landscape and Background

5

Background free

1 event /t /7d

5/t/y

1 event /kg/d

10 kg y 1 t y

Sens

itivi

ty (p

b)

10-10

10-9

10-8

10-7

10-6

Exposure (kg d) 10 103 102 104 105 106

Sensitivity (cm2)

10-46

10-45

10-44

10-43

10-42

W. Rau – SuperCDMS at SNOLAB May 2012

CDMS/SuperCDMS Collaboration

California Institute of Technology Z. Ahmed, S.R. Golwala, D. Moore, R. Nelson

Fermi National Accelerator Laboratory D. A. Bauer, J. Hall, D. Holmgren, L. Hsu, B. Loer, R.B. Thakur

Massachusetts Institute of Technology A. J. Anderson, E. Figueroa-Feliciano, S.A. Hertel, S.W. Leman, K.A. Mccarthy

NIST K. Irwin

Queen’s University C.H. Crewdson , P. C.F. Di Stefano , J. Fox, O. Kamaev, C. Martinez , P. Nadeau , K. Page , W. Rau, Y. Ricci, M.-A. Verdier

Santa Clara University B. A. Young

SLAC/KIPAC M. Asai, A. Borgland, D. Brandt, P.L. Brink,, E. Do Couto E Silva, G.L. Godrey, J. Hasi, M. Kelsey, C. J. Kenney, P. C. Kim, M.E. Monzani, R. Partridge, R. Resch, D. Wright

Southern Methodist University J. Cooley, B. Karabuga, H. Qiu, S. Scorza

Stanford University B. Cabrera, R. Moffat, M. Pyle, P. Redl, B. Shank, S. Yellin, J. Yen

Syracuse University R. Bunker, Y. Chen, M.. Kiveni, R. W. Schnee

Texas A&M R. Harris, A. Jastram, K. Koch, R. Mahapatra, J. Sander

University of California, Berkeley M. Daal, T. Doughty , N. Mirabolfathi, A. Phipps, B. Sadoulet, B. Serfass, D. Speller, K.M. Sundqvist

University of California, Santa Barbara D.O. Caldwell

University of Colorado Denver M.E. Huber

University of Florida R. Agnese, D. Balakishiyeva, T. Saab, B. Welliver

Universidad Autonoma de Madrid D. Credeño, L. Esteban

University of Minnesota H. Chagani, J. Beaty, P. Cushman, S. Fallows, M. Fritts, T. Hofer, V. Mandic, R. Radpour, A. Reisetter, A. Villano, J.Zhang

University of Zurich S. Arrenberg, T. Bruch, L. Baudis

6 Evidence

Results Dark M

atter Conclusion

CDMS

Super CDM

S


Evidence Dark M

atter Results

Conclusion CDM

S Super CDM

S CDMS Technology

Operating Principle

Phonon energy [keV]

Ioni

zatio

n en

ergy

[keV

eeq

]

Nuclear recoils from neutrons

Electron recoils from β’s and γ’s

Thermal coupling Thermal bath

Phonon sensor

Target

+ + + +

- - - -

+ +

+ +

- - - - -

- -

+ + + e n

• Phonon signal: measures energy deposition

• Ionization signal: quenched for nuclear recoils (lower signal efficiency)

• Allows us to distinguish potential signal from background

Phon

on si

gnal

Ch

arge

sign

al

Electron recoil Nuclear recoil

7 W. Rau – SuperCDMS at SNOLAB May 2012

Evidence Results

Dark Matter

Conclusion CDM

S Super CDM

S CDMS Technology

Detectors 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


Evidence Results

Dark Matter

Conclusion CDM

S Super CDM

S CDMS Technology

Detector Performance Io

niza

tion/

Reco

il en

ergy

Recoil energy [keV]

γ-band

n-band

γs

neutrons

βs

surface event

nuclear recoil

rising edge slope

Z -sensitive I onization and P honon detectors


Ioni

zatio

n/Re

coil

ener

gy

Recoil energy [keV]

β-band

γ-band

n-band

Evidence Results

Dark Matter

Conclusion CDM

S Super CDM

S The CDMS Family

SUF, 10 mwe

Soudan, 2100 mwe

SNOLAB, 6000 mwe

1998 - 2002 CDMS I 6 detectors 1 kg Ge (30 kgd ) σ < 3.5e-42 cm2

2003 - 2009

CDMS II 30 detectors ~4 kg Ge (400 kgd) σ < 3.5e-44 cm2

SuperCDMS @ Soudan 15 detectors 10 kg Ge (~2500 kgd) σ < 5e-45 cm2

2014 - 2017

SuperCDMS @ SNOLAB 80-90 detectors 100 kg Ge (~35000 kgd) σ < 2e-46 cm2

SuperCDMS test facility @ SNOLAB (2011)

exposures are after all cuts!

2009 - 2013


Evidence Results

Dark Matter

Conclusion CDM

S Super CDM

S CDMS at Soudan

Experimental Setup

„Tower“ (6 Detectors)

Cryostat, Coldbox Shielding

Soudan Underground lab (2000 m w.e.)

5 Towers (~ 5 kg Ge ) operated 2006 – 2008


Evidence Results

Conclusion CDM

S Dark M

atter Super CDM

S

Results Spin independent interaction


Dark Matter Data

XENON100

EDELWEISS 2009

CDMS 2009

CDMS 2010

Evidence Results

Conclusion CDM

S Dark M

atter Super CDM

S

Results Spin independent interaction

CDMS 2010

EDELWEISS II 2011

XENON100 – 100d

CDMS + EDELWEISS


CRESST 2009

CRESST 2011

Erde

Sun

Evidence Results

Conclusion CDM

S Dark M

atter Super CDM

S

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


Evidence Results

Conclusion CDM

S Dark M

atter Super CDM

S

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 WIMP rate

shoots up dramatically

WIMP Recoil Spectrum


Standard analysis range Low energy extension

CDMS Data

Evidence Results

Conclusion CDM

S Dark M

atter Super CDM

S

16

CDMS – Low Threshold Analysis SUF 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


Evidence Results

Conclusion CDM

S Dark M

atter Super CDM

S

17

Results Low mass WIMPs

DAMA

CoGeNT

CDMS 10 keV

CDMS, SUF

CDMS Soudan

XENON 100

PICASSO


CoGeNT interpretation by Hooper et al.

Recent CoGeNT reanalysis moved region down considerably (now avoids tension with CDMS data)

Evidence Results

Conclusion CDM

S Dark M

atter Super CDM

S

18

CDMS – Annual Modulation Analysis W. Rau – SuperCDMS at SNOLAB May 2012

5-11.9 keVnr CDMS data 5-11.9 keVnr CDMS data CoGeNT

• Test hypothesis that CoGeNT modulation is caused by nuclear recoils from a setup-independent source (such as dark matter)

• Need to convert energy scale (CoGeNT measures ionization only; CDMS uses phonon signal to determine energy)

Evidence Results

Conclusion CDM

S Dark M

atter Super CDM

S

19

CDMS – Annual Modulation Analysis

• Nuclear Recoil Hypothesis inconsistent with CDMS data

• What if it is Electron Recoils?

→ Would need to go to lower energy (work in progress; checking down to 2 keV is conceivable)


Evidence Results

Conclusion CDM

S Dark M

atter Super CDM

S SuperCDMS

Soudan

• 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 calculation

Phonon sensors on top and bottom


Evidence Results

Conclusion CDM

S Dark M

atter Super CDM

S SuperCDMS

Soudan

• New detectors tested underground • DAQ adjusted to new requirements • Increase total target mass (~10 kg) • Detectors cold since November;

started collecting dark matter data • Improve sensitivity by ~ x5-8 • Expect limitation from cosmogenic

background after 2-3 years of operation

Surface events


34,000 betas 0 events leakage

210Pb source

Evidence Results

Conclusion CDM

S Dark M

atter Super CDM

S SuperCDMS SNOLAB - Setup

SuperCDMS Setup at SNOLAB • Detector volume holds ~ 150 kg of active

target • Pb/Cu shielding against external radiation • PE shielding against neutrons • Neutron detector (monitor internal n flux,

veto neutrons interacting in Ge detectors) Shileding [mwe]

log

(Muo

n flu

x [m

-2s-1

])

Move to SNOLAB • Less Cosmic radiation • Cleaner environment • Good Lab

infrastructure • CFI proposal

submitted • Concurrent proposals

in US (DOE, NSF)


Evidence Results

Conclusion CDM

S Dark M

atter Super CDM

S SuperCDMS – Detector Test Facility

Underground at SNOLAB

Cryo

stat

W

ater

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 ground SUF cryostat being upgraded; installation planned in 2012

Motivation

Mostly neutron background

Recoil energy [keV]

Ioni

zatio

n yi

eld


Evidence Results

Conclusion CDM

S Dark M

atter Super CDM

S SuperCDMS at SNOLAB

Ladder Lab – Tentative Layout


Results Conclusion

CDMS

Super CDM

S Dark M

atter

Conclusion

• Strong observational evidence for the existence of dark matter • WIMPs are probably the best motivated candidates • 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; no evidence for annual modulation in CDMS data • SuperCDMS at Soudan (~10 kg, iZIP detectors) being commissioned • 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


Documents

Pushing the Limits: Dark Matter Search with SuperCDMS · Dark Matter. Conclusion •Strong observational evidence for the existence of dark matter •WIMPs are probably the best motivated