Status of the Cryogenic Dark Matter Search · TeVPA 8 Analysis Technique L o w y i e l d s i n g l...

24
Status of the Cryogenic Dark Matter Search Lauren Hsu Fermilab TeV Particle Astrophysics July 13, 2009

Transcript of Status of the Cryogenic Dark Matter Search · TeVPA 8 Analysis Technique L o w y i e l d s i n g l...

Page 1: Status of the Cryogenic Dark Matter Search · TeVPA 8 Analysis Technique L o w y i e l d s i n g l e s m a s k e d Candidate Criteria: • Data Qualty + Fiducial Volume Cut • Muon-veto

Status of the CryogenicDark Matter Search

Lauren HsuFermilab

TeV Particle AstrophysicsJuly 13, 2009

Page 2: Status of the Cryogenic Dark Matter Search · TeVPA 8 Analysis Technique L o w y i e l d s i n g l e s m a s k e d Candidate Criteria: • Data Qualty + Fiducial Volume Cut • Muon-veto

TeVPA 2009 2

Is Dark Matter a WIMP?

M. Attisha

Kolb & Turner, “The Early Universse”

particles with mass and annihilation cross section at the weak scale naturally yield correct relic density of CDM

χχ

qq

χ

χ-

q

q-

Look for nuclear recoil from WIMPscatter

Page 3: Status of the Cryogenic Dark Matter Search · TeVPA 8 Analysis Technique L o w y i e l d s i n g l e s m a s k e d Candidate Criteria: • Data Qualty + Fiducial Volume Cut • Muon-veto

TeVPA 2009 3

CDMS Experiment

CDMSII at Soudan:Five Towers (30 ZIPS)

operating since June ‘06

1 µ tungsten 380µ x 60µaluminum fins

Z-sensitiveIonization andPhonon detectors

Soudan Mine

Most sensitive to spin-independent scattering: σ∝ A2

4.75 kg Ge(A=73), 1.1 kg Si(A=28)

Page 4: Status of the Cryogenic Dark Matter Search · TeVPA 8 Analysis Technique L o w y i e l d s i n g l e s m a s k e d Candidate Criteria: • Data Qualty + Fiducial Volume Cut • Muon-veto

TeVPA 2009 4

Detection Strategydiscrimination and shielding maintain a <1 event background experiment

elec

tron re

coils

nuclear recoils

Ephonon

Ech

arge

4 phonon channels

(each is 1036Treansition EdgeSensors in parallel)

inner sensor+

outer guard

(phonon side)

(chargeside)

Signature of a Nuclear Recoil:reduced ionization signal relative to

phonon signal

Major Backgrounds:

• Gammas/Betas (electron recoils)

• Neutrons (nuclear recoils)• Surface Events

19 Ge zips (250 g each)

11 Si zips (100 g each)

1 cm thick crystals

Page 5: Status of the Cryogenic Dark Matter Search · TeVPA 8 Analysis Technique L o w y i e l d s i n g l e s m a s k e d Candidate Criteria: • Data Qualty + Fiducial Volume Cut • Muon-veto

TeVPA 2009 5

• 133Ba• 252Cf

Gamma Rejection

ionizationyield

Echarge

Ephonon

=

2σ electron recoil band

2 σ nuclear recoil band

BETTER THAN 1:104 rejection of gammas basedon ionization yield alone

elec

tron

rec

oils

nuclear recoils

Ephonon

Ech

arge

ancient lead shielding

ultra-clean materialsand careful handling

Page 6: Status of the Cryogenic Dark Matter Search · TeVPA 8 Analysis Technique L o w y i e l d s i n g l e s m a s k e d Candidate Criteria: • Data Qualty + Fiducial Volume Cut • Muon-veto

TeVPA 2009 6

Neutron Backgrounds

Soudan Mine: 2090 mwe

muon veto ~98% efficient

2 layers polyethylene -shields from cosmogenic and

radiogenic neutrons

(muon rate reduced by >104 ) << 1 unvetoedsingle scatter

neutron / kg /year

GEANT4

FLUKA+MCNPX

MUSIC

Neutrons maydouble scatter orbe accompanied by

EM shower

1. Go Deep: 2. Use Active Shielding:

3. Use Passive Shielding:

4. Use Event Topology

5. Run Extensive Simulations:

Page 7: Status of the Cryogenic Dark Matter Search · TeVPA 8 Analysis Technique L o w y i e l d s i n g l e s m a s k e d Candidate Criteria: • Data Qualty + Fiducial Volume Cut • Muon-veto

7

Surface Events10 µm “dead layer” results in reducedionization collection

• 133Ba• 252Cf

These events are primarily electrons,gammas and x-rays originating fromsurfaces of the detectors andsurrounding materials

Phonon pulse shape (timing) distinguishes surface events

Both yield and “timing” rejects these events

approximatesignal region

surfaceevent

nuclearrecoil

rising edge slope

Page 8: Status of the Cryogenic Dark Matter Search · TeVPA 8 Analysis Technique L o w y i e l d s i n g l e s m a s k e d Candidate Criteria: • Data Qualty + Fiducial Volume Cut • Muon-veto

TeVPA 8

Analysis Technique

Low yield singles masked

Candidate Criteria:• Data Qualty + Fiducial Volume Cut• Muon-veto anticoincident• Single Scatter (only 1 zip w/ signal)• Ionization yield within 2σ nuclear recoilband• Phonon “timing” cut - reject surfaceevents

All cuts established before unblinding!

Cut EfficienciesCDMSII 2008 result

Page 9: Status of the Cryogenic Dark Matter Search · TeVPA 8 Analysis Technique L o w y i e l d s i n g l e s m a s k e d Candidate Criteria: • Data Qualty + Fiducial Volume Cut • Muon-veto

TeVPA 2009 9

Our Current Limit

398 raw kg-d121 kg-d (for 60 GeV/c2 WIMP)

10 - 100 keV analysis range

Expected Surface Events:

PR

L 102, 011301 (2009)

(α,n): < 0.03(fission): < 0.1Cosmogenic: < 0.1 (MC 0.03-0.05)

Expected Neutrons:

ZERO Events Observedin Signal Region!

CDMS II 2008: 1st Five Tower Result

4.6x10-44cm2

@90% CL

Page 10: Status of the Cryogenic Dark Matter Search · TeVPA 8 Analysis Technique L o w y i e l d s i n g l e s m a s k e d Candidate Criteria: • Data Qualty + Fiducial Volume Cut • Muon-veto

10

coming soon…

Page 11: Status of the Cryogenic Dark Matter Search · TeVPA 8 Analysis Technique L o w y i e l d s i n g l e s m a s k e d Candidate Criteria: • Data Qualty + Fiducial Volume Cut • Muon-veto

TeVPA 2009 11

CDMS II 2009Projected Sensitivity

~2.5X moretotal

exposure

Ge Exposures:• CDMS II T1+T2 ~120 kg-d• CDMS II 2008 ~400 kg-d• CDMS II 2009 ~750 kg-d

Results expectedAugust ‘09

Baltz, Gandolo 2004Roszkowski et al. 2007, 95 % CLRoszkowski et al. 2007, 65% CLCDMS II T1+T2 Ge reanalysisZeplin III 2008XENON 10 2007CDMS II 2008 GeCDMS II 2008 Ge Combined

(after nominal quality cuts)

Page 12: Status of the Cryogenic Dark Matter Search · TeVPA 8 Analysis Technique L o w y i e l d s i n g l e s m a s k e d Candidate Criteria: • Data Qualty + Fiducial Volume Cut • Muon-veto

TeVPA 2009 12

Calibration Data Preview

• 133Ba• 252Cf

CDMS II 2008

Recoil Energy (keV)

Ioni

zatio

n Yi

eld

Initial studies indicate the data is very well behaved…even better than previously published data!

• 133Ba• 252Cf

CDMS II 2009

Recoil Energy (keV)

Ioni

zatio

n Yi

eld

tighter bands!

Page 13: Status of the Cryogenic Dark Matter Search · TeVPA 8 Analysis Technique L o w y i e l d s i n g l e s m a s k e d Candidate Criteria: • Data Qualty + Fiducial Volume Cut • Muon-veto

TeVPA 2009 13

Promising Surface EventRejection

Aiming for ~X2 better rejection of surface events to keep up with exposurepotential and stay a <1 background experiment

Note: Ba/Cf exposures are different between datasets andhasn’t been corrected for here

approximatesignal region

• 133Ba e-recoil

• 133Ba surface

• 252Cf n-recoil

Timing Parameter (µs)

Ioni

zatio

n Yi

eld

(shown for 1 zip)

Timing Parameter (µs)

- 2008 133Ba surface- 2008 252Cf neutron- 2009 133Ba surface- 2009 252Cf neutron

Surface EventDiscrimation

CDMS 2009 Calibration Data

Page 14: Status of the Cryogenic Dark Matter Search · TeVPA 8 Analysis Technique L o w y i e l d s i n g l e s m a s k e d Candidate Criteria: • Data Qualty + Fiducial Volume Cut • Muon-veto

TeVPA 2009 14

SuperCDMS

• modified Al fin layout, improves phononcollection efficiency

• cleaner, simplified, and streamlinedproduction

• “mercedes” phonon sensor layout, outerphonon “guard”

15 kg of Ge at Soudan, arranged as 5 SuperTowers

“mercedes” zip

SuperTower CDMSII Tower

• 2.5X thicker (1-inch)Ge crystals

• “endcap” Ge vetodetectors in each tower

Page 15: Status of the Cryogenic Dark Matter Search · TeVPA 8 Analysis Technique L o w y i e l d s i n g l e s m a s k e d Candidate Criteria: • Data Qualty + Fiducial Volume Cut • Muon-veto

TeVPA 2009 15

First SuperTower Installation

CDMS II data-takingended March 2009

First SuperTowerinstallation is now

complete!

Testing currentlyunderway

Page 16: Status of the Cryogenic Dark Matter Search · TeVPA 8 Analysis Technique L o w y i e l d s i n g l e s m a s k e d Candidate Criteria: • Data Qualty + Fiducial Volume Cut • Muon-veto

TeVPA 2009 16

SuperCDMS FutureCDMS II4 kg Ge

~ 2 yrs operation

SuperCDMS @ Soudan15 kg Ge

~ 2 yrs operation

SuperCDMS @ Snolab100 kg Ge

~ 3 yrs operation

DUSEL/GEODM1.5T

~LHCprojectedlimit

LHCbenchmarks

Page 17: Status of the Cryogenic Dark Matter Search · TeVPA 8 Analysis Technique L o w y i e l d s i n g l e s m a s k e d Candidate Criteria: • Data Qualty + Fiducial Volume Cut • Muon-veto

TeVPA 2009 17

summaryCDMS has a world-leading limit on the spin-independent WIMP

annihilation cross section:

4.6x10-44cm2 at 90% CL (for 60 GeV/c2 WIMP mass)

~750 kg-days of five-tower data is currently being analyzed.Results expected by end of summer

First SuperCDMS tower is installed and is nearly ready fordata-taking

Steady progress to zeptobarn cross sections and smaller!

Page 18: Status of the Cryogenic Dark Matter Search · TeVPA 8 Analysis Technique L o w y i e l d s i n g l e s m a s k e d Candidate Criteria: • Data Qualty + Fiducial Volume Cut • Muon-veto

TeVPA 2009 18

Thank You

Page 19: Status of the Cryogenic Dark Matter Search · TeVPA 8 Analysis Technique L o w y i e l d s i n g l e s m a s k e d Candidate Criteria: • Data Qualty + Fiducial Volume Cut • Muon-veto

TeVPA 2009 19

backup slides

Page 20: Status of the Cryogenic Dark Matter Search · TeVPA 8 Analysis Technique L o w y i e l d s i n g l e s m a s k e d Candidate Criteria: • Data Qualty + Fiducial Volume Cut • Muon-veto

TeVPA 2009 20

Other CDMS Results for2009

“Analysis of the low-energy electron-recoil spectrum ofthe CDMS experiment” - arXiv: 0907.1438 [astro-ph]

“Search for Axions with the CDMS Experiment”- arXiv:0902.4693 [hep-ex]

Page 21: Status of the Cryogenic Dark Matter Search · TeVPA 8 Analysis Technique L o w y i e l d s i n g l e s m a s k e d Candidate Criteria: • Data Qualty + Fiducial Volume Cut • Muon-veto

TeVPA 2009 21

Energy Resolution

Ionization Energy [keV] Phonon Energy [keV]

Ionization Energy [keV]

356 keV

Phonon Energy [keV]

356 keV

10.4 keV 10.4 keV

Page 22: Status of the Cryogenic Dark Matter Search · TeVPA 8 Analysis Technique L o w y i e l d s i n g l e s m a s k e d Candidate Criteria: • Data Qualty + Fiducial Volume Cut • Muon-veto

TeVPA 2009 22

Signal Region CDMSII 2008

PRL 102, 011301 (2009)

WithoutTiming Cut

WithTiming Cut

Page 23: Status of the Cryogenic Dark Matter Search · TeVPA 8 Analysis Technique L o w y i e l d s i n g l e s m a s k e d Candidate Criteria: • Data Qualty + Fiducial Volume Cut • Muon-veto

TeVPA 2009 23

What are Surface Events?

~10 μm“deadlayer”

-3V

carrier backdiffusion

Reduced charge yield due to chargecarrier back-diffusion in surface events.

Correlations to 210Pb contamination observed, most likely frombeta decays on surface of detectors

210Po taggedα-decays

210Pb taggedβ-decays

Page 24: Status of the Cryogenic Dark Matter Search · TeVPA 8 Analysis Technique L o w y i e l d s i n g l e s m a s k e d Candidate Criteria: • Data Qualty + Fiducial Volume Cut • Muon-veto

TeVPA 2009 24

What is Dark Matter?

Bullet Cluster

Rotational Curves WMAP 5-year

Strong Lensing