Results from the Results from the Cryogenic Dark Matter Search - - PowerPoint PPT Presentation

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Results from the Results from the Cryogenic Dark Matter Search - - PowerPoint PPT Presentation

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Results from the Results from the Cryogenic Dark Matter Search Cryogenic Dark Matter Search at Soudan Soudan Underground Laboratory Underground Laboratory at (CDMS II) (CDMS II) Jonghee Yoo Jonghee Yoo Fermilab Fermilab The Dark Side

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Results from the Results from the Cryogenic Dark Matter Search Cryogenic Dark Matter Search

at at Soudan Soudan Underground Laboratory Underground Laboratory

(CDMS II) (CDMS II)

Jonghee Yoo Jonghee Yoo

Fermilab Fermilab

The Dark Side of the Universe, Seoul Korea, 24 May 2005

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The Dark Side of the Universe, Seoul Korea J.Yoo (Fermilab)

2 2

Stanford University

P.L. Brink, B. Cabrera, C.L. Chang, J. Cooley, R.W. Ogburn, M. Pyle, S.Yellin

University of California, Berkeley

  • M. Daal, J. Filippini, A. Lu, V. Mandic, P.Meunier,
  • N. Mirabolfathi, B. Sadoulet, D.N. Seitz, B. Serfass,

K.M. Sundqvist

University of California, Santa Barbara

  • R. Bunker, D.O. Caldwell, R. Ferril, R. Mahapatra,
  • H. Nelson, J. Sander,

University of Colorado at Denver and Health Sciences Center

  • M. E. Huber

University of Florida

  • L. Baudis, S. Leclercq

University of Minnesota

  • P. Cushman, L. Duong, A. Reisetter

Brown University

M.J. Attisha, R.J. Gaitskell, J-P. F. Thompson

Case Western Reserve Univers ity

D.S. Akerib, C. Bailey, P. Brusov, M.R. Dragowsky, D.D.Driscoll, D. Grant, R. Hennings- Yeomans, S.Kamat, T.A. Perera, R.W.Schnee, G.Wang

Fermi National Accelerator Laboratory

D.A. Bauer, M.B. Crisler, R. Dixon, D. Holmgren, E.Ramberg, J.

  • J. Yoo

Yoo

Lawrence Berkeley National Laboratory

  • R. McDonald, R.R. Ross, A. Smith

National Institute for Standards and Technology

  • K. Irwin

Santa Clara University

B.A. Young

CDMS II Collaboration

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The Dark Side of the Universe, Seoul Korea J.Yoo (Fermilab)

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Evidences of the Missing Components

Rotation Rotation curves curves of

  • f galaxies

galaxies Gravitational Lensing Gravitational Lensing Large Large Scale Scale Structure Structure Galaxy clusters Galaxy clusters SuperNova Ia SuperNova Ia CMB CMB

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The Dark Side of the Universe, Seoul Korea J.Yoo (Fermilab)

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Budget of the Universe

Baryonic Dark Matter Dust, Gas MACHOs Upper limit by BBN light element ratio observations Hot Dark Matter Upper limit from CMB, tritium decay neutrino mass Ων < 0.0155 Cold Dark Matter WIMPs / Axions / …

In the picture of ΛCDM model WMAP and SDSS observations

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The Dark Side of the Universe, Seoul Korea J.Yoo (Fermilab)

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World Map of Dark Matter & Where We Are

  • L. Roszkowski

CDMS Limit Plotter for Public : http://dmtools.brown.edu

90%CL

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The Dark Side of the Universe, Seoul Korea J.Yoo (Fermilab)

6 6

  • Spherical Halo Model

Spherical Halo Model

  • Energy spectrum & rate depend on WIMP distribution in Dark Matter Halo

Energy spectrum & rate depend on WIMP distribution in Dark Matter Halo – – Assume isothermal Maxwell-Boltzmann velocity distribution Assume isothermal Maxwell-Boltzmann velocity distribution – – Vo= 230 Vo= 230 km/s km/s (WIMP velocity against detector) (WIMP velocity against detector) – – Vesc= Vesc= 650 650 km/s km/s (escape velocity of WIMP (escape velocity of WIMP from galactic halo) from galactic halo) – – ρ ρ = 0.3 GeV / cm = 0.3 GeV / cm3

3

– – Energy spectrum of recoils is featureless exponential with Energy spectrum of recoils is featureless exponential with <E> ~ 50 <E> ~ 50 keV keV

WIMP Distribution in the Universe

Photo from Z.Frei and E.Gunn

dR dE f (v) v

vmin vesc

  • dv

( ~ 1/r

2)

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The Dark Side of the Universe, Seoul Korea J.Yoo (Fermilab)

7 7

Invisible …

Yoo steal this figure from http://dmrc.snu.ac.kr

Now here is secret of CDMS, a very simple secret: If you can not see… What is essential is invisible to the eye. Listen!

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The Dark Side of the Universe, Seoul Korea J.Yoo (Fermilab)

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WIMP Detection Strategy of CDMS

Interaction Rate ∝A2

Use both Ge(73) and Si(28) targets R(Si/Ge) = ~1/6

Weakly Interacting

WIMP mean free path in Ge ~ 1010m The event will single scatter

WIMP

Direct detection of WIMP signal Nuclei recoil by elastic scattering Read out phonons from recoil together with ionization signal

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The Dark Side of the Universe, Seoul Korea J.Yoo (Fermilab)

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CDMS Detector

Al

Transition Edge Sensor Ge or Si quasiparticle diffusion phonons 1 µ tungsten 380µ x 60µ aluminum fins ElectroThermal Feedback R T

Tc~80mK

~10mK

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The Dark Side of the Universe, Seoul Korea J.Yoo (Fermilab)

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CDMS Detector Readout

Phonon sensor

Recoil energy

A C B D

Phonon signal From a quadrant

Charge sensor

Ionization energy Charge signal From inner electrode

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The Dark Side of the Universe, Seoul Korea J.Yoo (Fermilab)

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WIMP event and Background

χ0

v/c ≈ 7×10-4 Nucleus Recoils Less ionization WIMP event

Er Er

Electron Recoils

γ

v/c ≈ 0.3 Background More ionization

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The Dark Side of the Universe, Seoul Korea J.Yoo (Fermilab)

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WIMP Signal and Background

Photons Neutrons Photons Neutrons

Yield = E(ionization) / E(recoil)

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The Dark Side of the Universe, Seoul Korea J.Yoo (Fermilab)

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WIMP Candidate Signal (a fake example)

VETOs

TOWER 1 TOWER 2

Time[us] Time[us]

0 200 400 600 800 1000 1200 0 200 400 600 800 1000 1200

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The Dark Side of the Universe, Seoul Korea J.Yoo (Fermilab)

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Statistical Discrimination of neutron background

1. Measure the rate of multiple interaction 2. Compare the rates in Si vs Ge : WIMP cross sections scale as A2, while neutron rates will be comparable

To prevent neutron background

1. Go deep underground to reduce the cosmogenic production of neutrons 2. Veto out cosmic muons : active shield 3. Shield the detectors with lead and polyethylene : passive shield

Neutron Background

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The Dark Side of the Universe, Seoul Korea J.Yoo (Fermilab)

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CDMS at Stanford (Single Tower)

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

200 200 muons muons /sec /sec in 4 m in 4 m2

2 shield

shield Kolar (India) Sudbury (Canada)

Mont Blanc (France) Baksan (Russia)

Oroville (USA)

Boulby (UK) Frejus (France) Soudan (USA) Stanford Stanford Underground Site Underground Site Gran Sasso (Italy)

  • 2001-2002 operation at shallow site (17 mwe)

– 28 kg-days net exposure of 4 x 250g Ge detectors and 2 x 100g Si detectors – 20 nuclear-recoil candidates consistent with expected neutron background – PRD 68, 082002 (2003) : Single Tower Results from Stanford

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The Dark Side of the Universe, Seoul Korea J.Yoo (Fermilab)

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  • 2003 operation at deeper site

– 2090 m.w.e @ Soudan Mine (5 x 10^4 fewer muons) – Reduced neutron background from ~1/kg/day to ~1/kg/year

CDMS II at Soudan (Single Tower)

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

Kolar (India) Sudbury (Canada)

Mont Blanc (France) Baksan (Russia)

Oroville (USA)

Boulby (UK) Frejus (France) Soudan (USA) Stanford Stanford Underground Underground Site Site Gran Sasso (Italy)

1 1 muons muons / min / min in 4 m in 4 m2

2 shield

shield

200 200 muons/sec muons/sec in 4 m in 4 m2

2 shield

shield

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The Dark Side of the Universe, Seoul Korea J.Yoo (Fermilab)

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Experimental Setup in the Soudan Mine

MINOS CDMS

780m (2090mwe) Surface

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The Dark Side of the Universe, Seoul Korea J.Yoo (Fermilab)

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Low Activity Lead Polyethylene µ-metal (with copper inside) Ancient lead 41 cm 23 14

Detector Shielding

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The Dark Side of the Universe, Seoul Korea J.Yoo (Fermilab)

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World Wide WIMP sports

Soudan Mine

vs

Yang-Yang

Steal from : http://dmrc.snu.ac.kr/

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The Dark Side of the Universe, Seoul Korea J.Yoo (Fermilab)

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CDMS II at Soudan (Single Tower)

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

Kolar (India) Sudbury (Canada)

Mont Blanc (France) Baksan (Russia)

Oroville (USA)

Boulby (UK) Frejus (France) Soudan (USA) Stanford Underground Stanford Underground Site Site Gran Sasso (Italy)

1 per min 1 per min in 4 m in 4 m2

2 shield

shield 200 Hz 200 Hz muons muons in 4 m in 4 m2

2 shield

shield

  • 2003 operation at deeper site

– 2090 m.w.e @ Soudan Mine (5 x 10^4 fewer muons) – Reduced neutron background from ~1/kg/day to ~1/kg/year – 19.4 kg-days net exposure – PRL 93, 211301 (2004) : Single Tower Results @Soudan Mine

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The Dark Side of the Universe, Seoul Korea J.Yoo (Fermilab)

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H Hot results

  • t results

from really Cool from really Cool Two Tower Two Tower

  • peration at
  • peration at Soudan

Soudan

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The Dark Side of the Universe, Seoul Korea J.Yoo (Fermilab)

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SQUID cards FET cards

2 towers operation (25 Mar ~ 8 Aug 2004)

6 Ge (6 x 0.25kg) and 6 Si (6 x 0.1kg) detectors Detector live time : 74 days

In this talk, Results from Ge detectors will be discussed

Ge Ge Ge Ge Ge Ge Si Si Si Si Si Si

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The Dark Side of the Universe, Seoul Korea J.Yoo (Fermilab)

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Am241 :

γ 14, 18, 20, 26, 60 kev

Cd109 + Al foil :

γ 22 kev

Cd109 :

γ 22 kev i.c. electr 63, 84 KeV

Position reconstruction

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The Dark Side of the Universe, Seoul Korea J.Yoo (Fermilab)

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Ionization Energy Recoil Energy

dN/dE dN/dE

Ionization Energy (keV) Recoil Energy (keV)

Energy resolution is good enough (< 5%)

Photon Calibration with 133Ba

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The Dark Side of the Universe, Seoul Korea J.Yoo (Fermilab)

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Nuclear recoils in Nuclear recoils in Ge Ge detector detector Nuclear recoils in Nuclear recoils in Si Si detector detector

Nuclear-recoil calibration with 252Cf

Excellent agreement between data and Monte Carlo → Crucial to understand cut efficiencies

. Data

  • - MC

. Data

  • - MC
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The Dark Side of the Universe, Seoul Korea J.Yoo (Fermilab)

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Ionization Yield Recoil Energy (keV)

10 20 30 40 50 60 70 80 90 100

1.5 1.0 0.5 0.0

23x of WIMP-search data sample

Setting Cuts Blind with Calibration Data

252Cf neutron 133Ba γ source

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The Dark Side of the Universe, Seoul Korea J.Yoo (Fermilab)

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Rejects Electrons (rise time cut)

Neutrons from 252Cf source

gammas Surface- electron recoils

Accept

Δt at 10 ~ 40% of pulse height Rise Time

Yield (ionization/recoil) Phonon e

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The Dark Side of the Universe, Seoul Korea J.Yoo (Fermilab)

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Rejects Electrons (delay time cut)

Photons from

133Ba Source

neutrons charge phonon Delay time

Yield (ionization/recoil) e

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The Dark Side of the Universe, Seoul Korea J.Yoo (Fermilab)

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Surface events from calibration source neutrons from calibration source

Estimate Number of Background Event

Scaled phonon delay + rise time

Estimated Background

0.37 ± 0.15 (stat.) ±0.20 (syst.) (syst.) Preliminary Cut Efficiency

All cut set blind

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The Dark Side of the Universe, Seoul Korea J.Yoo (Fermilab)

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Ionization Yield Recoil Energy (keV)

10 20 30 40 50 60 70 80 90 100

1.5 1.0 0.5 0.0

23x of WIMP-search data sample

Setting Cuts Blind with Calibration Data

252Cf neutron 133Ba γ source

Before Timing Cut After Timing Cut

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The Dark Side of the Universe, Seoul Korea J.Yoo (Fermilab)

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Analysis Results : WIMP search data

Ionization Yield Recoil Energy (keV)

Before timing cut

an event here a near miss Open data on

March 31, 2005

All the cut was blind

72 live-days, 1.25kg Ge detectors Estimated Background After timing cut 0.37 ± 0.15 (stat.) ±0.20 (syst.)

After timing cut (reject electrons)

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The Dark Side of the Universe, Seoul Korea J.Yoo (Fermilab)

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Experimental WIMP limits (Spin Independent)

Standard Assumption

Spherical halo model MB velocity distribution Vo= 230 km/s Vesc= 650 km/s ρ= 0.3 GeV / cm3 Factor 10x better WIMP search sensitivity than any other experiments

ZEPLIN I EDELWEISS CDMS (1 tower @Stanford) CDMS (1 tower @Soudan) CDMS (2 tower @Soudan) CDMS (1 + 2 tower combined)

90%CL

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The Dark Side of the Universe, Seoul Korea J.Yoo (Fermilab)

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What What’ ’s next? s next?

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The Dark Side of the Universe, Seoul Korea J.Yoo (Fermilab)

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5 Tower Operation is almost Ready

30 detectors (5 towers x 6 detectors) – 4.75 kg of Ge, 1.1 kg of Si detectors – Run through 2006 – Improve Sensitivity further 10x

Now Now Commisioning Commisioning

CDMS II Projected

Result today

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The Dark Side of the Universe, Seoul Korea J.Yoo (Fermilab)

35 35 SuperCDMS SuperCDMS SuperCDMS

1000 kg (factor 100)

SuperCDMS development CDMS II

SuperCDMS Project

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The Dark Side of the Universe, Seoul Korea J.Yoo (Fermilab)

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SuperCDMS Phase A 25 kg of Ge (2011) SuperCDMS Phase B 150 kg of Ge (2014) SuperCDMS Phase C 1000 kg of Ge (2018)

SuperCDMS Reach

Result today (preliminary)

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The Dark Side of the Universe, Seoul Korea J.Yoo (Fermilab)

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Summary

CDMS II Results at Soudan

– Analysis of two tower operation is nearly done

  • Results from Ge detectors are discussed
  • Results from other detectors are coming soon
  • Detailed systematic check is underway

– No signs of WIMPs

  • Spin Independent-Limits now 10x lower than any other experiment
  • Starting to probe mSUGRA region
  • World’s strongest constraints on SD WIMP-neutron coupling

– Five tower operation is now (2005) commissioning, through 2006

  • Additional 10 x lower than current limits are expected
  • Or discover WIMPs.