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Results from the CDMS Experiment Jodi Cooley Stanford University - - PowerPoint PPT Presentation

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Results from the CDMS Experiment Jodi Cooley Stanford University CDMS Analysis Coordinator TAUP 09 Jodi Cooley - Stanford University 1 CDMS II Collaboration Caltech Syracuse University Z. Ahmed, J. Filippini, S. R. Golwala, D. Moore,

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TAUP 09 Jodi Cooley - Stanford University

Results from the CDMS Experiment

Jodi Cooley Stanford University CDMS Analysis Coordinator

1

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TAUP 09 Jodi Cooley - Stanford University

CDMS II Collaboration

2 Caltech

  • Z. Ahmed, J. Filippini, S. R. Golwala, D. Moore,
  • R. W. Ogburn

Case Western Reserve University

  • D. S. Akerib, K. Clark, C. N. Bailey, D. R. Grant,
  • R. Hennings-Yeomans, M.R. Dragowsky

Fermilab

  • D. A. Bauer, F. DeJongh J. Hall, L. Hsu, D. Holmgren,
  • E. Ramberg, J. Yoo

MIT

  • E. Figueroa-Feliciano, S. Hertel, S. Leman, K. McCarthy

NIST

  • K. Irwin

Queens University

  • W. Rau

Santa Clara University

  • B. A. Young

Stanford University P.L. Brink, B. Cabrera, J. Cooley, M. Pyle, S. Yellin Syracuse University R.W. Schnee, M. Kos, J. M. Kiveni Texas A&M

  • R. Mahapatra

University of California, Berkeley

  • M. Daal,, N. Mirabolfathi, B. Sadoulet, D. Seitz, B. Serfass,
  • D. Seitz, K. Sundqvist

University of California, Santa Barbara

  • R. Bunker, D. O. Caldwell, H. Nelson, J. Sanders

University of Colorado at Denver

  • M. E. Huber

University of Florida

  • T. Saab, D. Balakishiyeva

University of Minnesota

  • P. Cushman, L. Dong, M. Fritts,
  • V. Mandic, X. Qiu, O. Kamaev,
  • A. Reisetter

University of Zurich

  • S. Arrenberg, T. Bruch, L. Baudis, M. Tarka
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TAUP 09 Jodi Cooley - Stanford University

CDMS II: The Big Picture

3

Use a combination of discrimination and shielding to maintain a “<1 event expected background” experiment with low temperature semiconductor detectors

Discrimination from measurements of ionization and phonon energy.

ER background NR signal Ephonon Echarge

Keep backgrounds low as possible through shielding.

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TAUP 09 Jodi Cooley - Stanford University

CDMS II ZIP Detectors

  • Z-sensitive Ionization and

Phonon mediated

  • 250 g Ge, 100 g Si crystals

1 cm thick, 7.5 cm diameter

  • Photolithographically patterned

to collect phonon and ionization signals

  • xy position imaging
  • surface rejection from pulse

shapes

  • 30 detectors stacked into 5

towers of 6 detectors

4 1 µ tungsten 380µ x 60µ aluminum fins

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TAUP 09 Jodi Cooley - Stanford University

ZIP Detectors: Charge

5 h+

  • 3V

h+ h+ e- e- e-

  • 3V
  • Vetoed by guard ring

Vetoed by guard ring

~85% ~15%

  • Inner Channel: Ionization Measurement
  • Outer Channel: Fiducial Volume
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SLIDE 6

TAUP 09 Jodi Cooley - Stanford University

ZIP Detectors: Phonons

6

Al Collector W Transition- Edge Sensor Si or Ge quasiparticle diffusion phonons

~

RTES (Ω)

4 3 2 1

T (mK) Tc ~ 80mK ~ 10mK

Tungsten Transition Edge Sensor (TES)

4 SQUID readout channels, each reads out 1036 TESs in parallel

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TAUP 09 Jodi Cooley - Stanford University

Background Rejection

7

  • Most backgrounds (e, γ)

produce electron recoils

  • WIMPS and neutrons

produce nuclear recoils.

Different particles, different interactions

  • M. Attisha

Different Particles, Different Interactions

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SLIDE 8

TAUP 09 Jodi Cooley - Stanford University

Background Rejection

8

  • Most backgrounds (e, γ)

produce electron recoils

  • WIMPS and neutrons

produce nuclear recoils.

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SLIDE 9

TAUP 09 Jodi Cooley - Stanford University

Background Rejection

8

  • Most backgrounds (e, γ)

produce electron recoils

  • WIMPS and neutrons

produce nuclear recoils.

  • Ionization yield (ionization

energy per unit phonon energy) strongly depends

  • n particle type.
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SLIDE 10

TAUP 09 Jodi Cooley - Stanford University

Background Rejection

8

  • Most backgrounds (e, γ)

produce electron recoils

  • WIMPS and neutrons

produce nuclear recoils.

  • Ionization yield (ionization

energy per unit phonon energy) strongly depends

  • n particle type.

10 20 30 40 50 60 70 80 90 100 0.5 1 1.5 Recoil Energy (keV) Ionization yield

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TAUP 09 Jodi Cooley - Stanford University

Background Rejection

9

  • Most backgrounds (e, γ)

produce electron recoils

  • WIMPS and neutrons

produce nuclear recoils.

  • Particles that interact in the

“surface dead layer” result in reduced ionization yield.

10 20 30 40 50 60 70 80 90 100 0.5 1 1.5 Recoil Energy (keV) Ionization yield

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TAUP 09 Jodi Cooley - Stanford University

Background Rejection

9

  • Most backgrounds (e, γ)

produce electron recoils

  • WIMPS and neutrons

produce nuclear recoils.

  • Ionization yield (ionization

energy per unit phonon energy) strongly depends

  • n particle type.
  • Particles that interact in the

“surface dead layer” result in reduced ionization yield.

10 20 30 40 50 60 70 80 90 100 0.5 1 1.5 Recoil Energy (keV) Ionization yield

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TAUP 09 Jodi Cooley - Stanford University

Reduced Ionization Yield

  • Reduced charge yield

due to charge carrier back-diffusion in surface events.

  • “Dead-Layer” is

within ~10 μm of detector surface.

10 ~10 μm “dead layer”

  • 3V

carrier back diffusion

h+ h+ h+ h+ h+ e- e- e- e- e- e- h+

rapid phonon down-conversion

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TAUP 09 Jodi Cooley - Stanford University

Surface Event Rejection

11

Phonons near surface travel faster, resulting in shorter risetimes of phonon pulse. Selection criteria set to accept ~0.5 background events to preserve maximum nuclear recoil acceptance.

Bulk Surface

Delay + RiseTime [µs] Counts

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TAUP 09 Jodi Cooley - Stanford University

Another View of Discrimination

12

5 10 15 20 25 30 0.2 0.4 0.6 0.8 1 Timing Parameter (µs) Ionization Yield

Bulk electron recoils Surface electron recoils Nuclear recoils

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TAUP 09 Jodi Cooley - Stanford University

Peeling the Shield Onion

13

Active Muon Veto:

rejects events from cosmic rays

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TAUP 09 Jodi Cooley - Stanford University

Peeling the Shield Onion

14

Active Muon Veto:

rejects events from cosmic rays

Polyethyene: moderate

neutrons produced from fission decays and from (α,n) interactions resulting from U/Th decays

Pb: shielding from gammas

resulting from radioactivity

Low Activity Lead Polyethylene µ-metal (with copper inside) Ancient lead 40 cm 22.5 cm 10 cm

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TAUP 09 Jodi Cooley - Stanford University

Peeling the Shield Onion

15

Active Muon Veto:

rejects events from cosmic rays

Polyethyene: moderate

neutrons produced from fission decays and from (α,n) interactions resulting from U/Th decays

Pb: shielding from gammas

resulting from radioactivity

Cu: shielding from gammas

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TAUP 09 Jodi Cooley - Stanford University

Peeling the Shield Onion

16

Active Muon Veto:

rejects events from cosmic rays

Polyethyene: moderate

neutrons produced from fission decays and from (α,n) interactions resulting from U/Th decays

Pb: shielding from gammas

resulting from radioactivity

Cu: shielding from gammas

NOTE: Cu lids for transport only.

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TAUP 09 Jodi Cooley - Stanford University

Peeling the Shield Onion

16

Active Muon Veto:

rejects events from cosmic rays

Polyethyene: moderate

neutrons produced from fission decays and from (α,n) interactions resulting from U/Th decays

Pb: shielding from gammas

resulting from radioactivity

Cu: shielding from gammas

@ 40 mK!!

Phonon Sensors

NOTE: Cu lids for transport only.

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TAUP 09 Jodi Cooley - Stanford University

17

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TAUP 09 Jodi Cooley - Stanford University

18

Log10(Muon Flux) (m-2s-1) Depth (meters water equivalent)

SUF 17 mwe 0.5 n/d/kg

(182.5 n/y/kg)

Soudan 2090 mwe 0.05 n/y/kg SNOLAB 6060 mwe 0.2 n/y/ton

(0.0002 n/y/kg)

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TAUP 09 Jodi Cooley - Stanford University

19

CDMS II Experiment

T1 T2 T3 T5 T4

  • 30 detectors installed and operating in

Soudan since June 06.

  • 4.75 kg of Ge, 1.1 kg of Si
  • Seven Total Data Runs:
  • R123 - R124:
  • taken: (10/06 - 3/07) (4/07 - 7/07)
  • exposure: ~400 kg-d (Ge “raw”)
  • PRL 102, 011301 (2009)
  • R125 - R128
  • taken: (7/07 - 1/08) (1/08 - 4/08)

(5/08 - 8/08) (8/08 - 9/08)

  • exposure: ~ 750 kg-d (Ge “raw”)
  • Under Analysis
  • R129:
  • taken: (11/08 - 3/09)
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TAUP 09 Jodi Cooley - Stanford University

First Five Tower Results

20

Blind Analysis:

Event selection and efficiencies were calculated without looking at the signal region of the WIMP-search data.

Event Selection:

Veto-anticoincidence cut Single-scatter cut Qinner (fiducial volume) cut Ionization yield cut Phonon timing cut

20 40 60 80 100 0.5 1 1.5 Recoil energy (keV) Ionization yield

Low yield singles masked

PRL 102, 011301 (2009)

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TAUP 09 Jodi Cooley - Stanford University

Analysis Summary

21

Neutron Backround

Poly Cu (α,n): < 0.03 Pb (fission): < 0.1 Cosmogenic: < 0.1 (MC 0.03-0.05) 8 vetoed neutron multiples seen 0 vetoed singles seen

5 10 15 20 25 30 35 40 45 50 0.2 0.4 0.6 0.8 1 Recoil energy (keV) Nuclear recoil acceptance Quality, Singles, Veto Fiducial volume Nuclear recoil band Phonon timing

398 raw kg-d 121 kg-d WIMP equiv. @ 60 GeV/c2 (10 - 100 keV analysis energy range)

Estimated number of background events to pass surface cut in Ge

Surface Background

0.6+0.5

−0.3(stat.)+0.3 −0.2(syst.)

PRL 102, 011301 (2009)

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TAUP 09 Jodi Cooley - Stanford University

CDMS II Results

22

PRL 102, 011301 (2009) 20 40 60 80 100 0.2 0.4 0.6 Recoil energy (keV) Ionization yield 0.2 0.4 0.6 Ionization yield

NO EVENTS OBSERVED!

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TAUP 09 Jodi Cooley - Stanford University

CDMS II Results

23

Upper limit at the 90% C.L.

  • n the WIMP-nucleon cross-

section is 4.6 x 10-44 cm2 for a WIMP

  • f mass 60 GeV/c2

WIMP mass [GeV/c2] Spin!independent cross section [cm2]

10

1

10

2

10

3

10

!44

10

!43

10

!42

10

!41

10

!40

Baltz Gondolo 2004 Roszkowski et al. 2007 95% CL Roszkowski et al. 2007 68% CL EDELWEISS 2005 WARP 2006 ZEPLIN II 2007 CDMS II 1T+2T Ge Reanalysis XENON10 2007 CDMS II 2008 Ge CDMS II Ge combined

PRL 102, 011301 (2009)

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TAUP 09 Jodi Cooley - Stanford University

Yield Discrimination

24

Previous Analysis Current Analysis

PRL 102, 011301 (2009)

  • 133Ba
  • 252Cf

Recoil Energy (keV) Ionization Yield

  • 133Ba
  • 252Cf

Recoil Energy (keV) Ionization Yield

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TAUP 09 Jodi Cooley - Stanford University

Peak at Timing Quantities

25

Previous Analysis Current Analysis

PRL 102, 011301 (2009)

Timing Parameter Timing Parameter

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TAUP 09 Jodi Cooley - Stanford University

Another View of Discrimination

26

Previous Analysis Current Analysis

PRL 102, 011301 (2009)

  • 133Ba ER
  • 133Ba SE
  • 252Cf

Timing Parameter Ionization Yield

  • 133Ba ER
  • 133Ba SE
  • 252Cf

Timing Parameter Ionization Yield

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TAUP 09 Jodi Cooley - Stanford University

Projected Sensitivity (2009)

27

WIMP Mass [GeV/c2] Cross-section [cm2] (normalised to nucleon) 10

1

10

2

10

3

10

  • 44

10

  • 43

10

  • 42

~2.5 times more total exposure

Baltz, Gandolo 2004 Roszkowski et al. 2007, 95 % CL Roszkowski et al. 2007, 65% CL CDMS II T1+T2 Ge reanalysis Zeplin III 2008 XENON 10 2007 CDMS II 2008 Ge CDMS II 2008 Ge Combined

Raw Exposure

  • R118-R119 = ~120 kg-d
  • Run 123-124= ~400 kg-d
  • Run 125-128 = ~750 kg-d

Results expected late Aug. 09

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TAUP 09 Jodi Cooley - Stanford University

Next Step: SuperCDMS

  • Last CDMS II data run taken on March 18, 2009
  • March 19, 2009: Warm up to begin the installation and

commissioning of the first SuperCDMS detectors

  • First step in realization of the proposed SuperCDMS Soudan

project (15 kg Ge deployed in existing Soudan setup)

  • SuperTowers 1-2 funded
  • SuperTowers 3-5 under review
  • Eventual goal: SuperCDMS SNOLAB (100 kg Ge deployed

at SNOLAB)

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TAUP 09 Jodi Cooley - Stanford University

What is a SuperTower?

29

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TAUP 09 Jodi Cooley - Stanford University

Detector Improvements

30

  • 1” - thick Ge crystal
  • Better phonon sensor

design

  • improves phonon signal

to noise

  • Optimized sensor layout
  • better rejection of

surface events

  • ST = five 1-inch detectors +

two 1-cm veto detectors

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TAUP 09 Jodi Cooley - Stanford University

ST1 Surface Testing

31

Before Timing Applied After Timing Applied

Recoil Energy (keV) Ionization Yield Recoil Energy (keV) Ionization Yield

  • 133Ba
  • 252Cf
  • 133Ba
  • 252Cf
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TAUP 09 Jodi Cooley - Stanford University

SuperTower 1 Installation

32

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TAUP 09 Jodi Cooley - Stanford University

SuperTower 1 Installed

33

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TAUP 09 Jodi Cooley - Stanford University

SuperCDMS Schedule

34

Activity Name

2008 2009 2010 2011 2012 2013 2014 2015 2016 2008 2009 2010 2011 2012 2013 2014 2015 2016

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

CDMS II

Operations 4kg, 2E-44 cm2 Expected Sensitivity

SuperCDMS Soudan

Detector R&D Construction Operations Expected Sensitivity 15 kg, 5E-45 cm2

SuperCDMS SNOLAB

Detector R&D Construction

SNOLAB facility 100 kg detector payload

Operations

100 kg detector payload

Expected Sensitivity

100 kg sensitivity

100 kg, 3E-46 cm2

GEODM...

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TAUP 09 Jodi Cooley - Stanford University

From CDMS to SuperCDMS to GEODM

35

χ1

0 Mass [GeV/c2]

σSI [cm2]

CDMS II Current CDMS II Final 15kg @ Soudan 100kg @ SNOLAB 1.5T @ DUSEL 1 2 3 4

10

2

10

3

10

−47

10

−46

10

−45

10

−44

10

−43

10

−42

SuperCDMS CDMS II

7.5 cm x 1 cm ~ 0.25 kg / det 16 detectors = 4 kg ~ 2 yrs operation 7.5 cm x 1 in ~ 0.64 kg / det

SuperCDMS SNOLAB and Germanium Observatory for Dark Matter (GEODM)

15 cm x 2 in ~ 5.1 kg / det Soudan 25 detectors ~ 15 kg 2 yrs ~ 8000 kg-d SNOLAB 150 detectors ~ 100 kg 3 yrs ~ 38,000 kg-d

SNOLAB 20 detectors ~ 100 kg 3 yrs ~ 100,000 kg-d DUSEL 300 detectors ~ 1.5 T 4 yrs ~ 1.5 Mkg-d

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TAUP 09 Jodi Cooley - Stanford University

Conclusions

36

  • Data taken between Oct. 2006 and July 2007 has been analyzed

and a cross section limit of < 4.6 x 10-44cm2 (90% CL) was placed for a WIMP of mass 60 GeV/c2.

  • CDMS II finished taking data on March 18, 2009. We are

currently analyzing the last data sets.

  • SuperCDMS is an experiment under development by the CDMS

collaboration which is planned for operation in Soudan. For this purpose we have enhanced the design of the CDMS detector.

  • The first SuperTower has been installed at Soudan and is under
  • commission. Initial tests on the surface are promising.
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TAUP 09 Jodi Cooley - Stanford University

Backups

37

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TAUP 09 Jodi Cooley - Stanford University

Improved Bkgrd Rejection

38

  • ld design

(quad = BMW) new design (Mercedes) energy partition “radius” [fractional] timing delay “radius” [µs]

phonon pulse rise time [µs] phonon pulse rise time [µs]

energy partition “radius” [fractional inner/outer energy partition [signed fractional] Exposure to Photon Source (= bulk events only)

variation in rise time entirely due to position dependence

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TAUP 09 Jodi Cooley - Stanford University

6” Detector R&D

39

  • Why larger detectors?
  • Reduce surface/volume ratio - decreases background
  • Ease of manufacture for large scale detectors
  • How?
  • Dislocation-free crystals can be grown up to 30 cm in diameter
  • Impurities not a problem for CDMS. We create metastable

states where impurities are neutralized and do not trap drifting charge.