Dark matter direct detection Alvaro E Chavarria KICP at The - - PowerPoint PPT Presentation

Alvaro E Chavarria KICP at The University of Chicago

Dark matter direct detection

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• Dark matter direct detection.
• DAMA and new NaI experiments.
• Recent results from PICO.
• Recent results from DarkSide.
• DAMIC experiment.
• The future of direct detection.

2

Overview

• Cold dark matter is needed for CMB cosmology...
• ... and structure formation.
• ... and to explain galaxy rotation curves.
• ... and evident from gravitational lensing.
• Overall 5.5 times more dark than baryonic matter.
• Local density may be non-zero.
• Could be made of particles...
• ... that could interact with SM particles.
• Numerology: “WIMP Miracle,” asymmetric DM, etc.

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Dark matter

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Direct detection

Xe Ge Ar Si Ne

arXiv:1310.8327v2 [hep-ex]

Mass: 100 GeV Mass: 1 TeV

χ

From galactic halo Nucleus

• n Earth

Recoil

B.Loer Thesis

Eχ ∼ Mχc2 GeV keV

• Large target mass many targets.
• Count for long time .
• Lowest possible threshold , to increase

fraction of recoil spectrum probed .

• Lowest possible background <1 event kg-1 y-1:

low radioactivity environment, nuclear/electron recoil discrimination.

• Large atomic mass increases total rate

(coherent scattering) but increases minimum WIMP mass probed .

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MT

T

Eth

f

A

Mmin

Direct detection

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Technologies

Noble liquid TPCs LUX/LZ XENON DarkSide ArDM Panda-X Scintillators DAMA/LIBRA ANAIS SABRE DM-Ice KIMS DEAP/CLEAN XMASS Ionization CoGeNT CDMS-HV CDEX DAMIC Phonon + Ionization CDMS-II SuperCDMS EDELWEISS Superheated PICO Phonon + Scintillation CRESST Nuclear recoil discrimination

Locations

5/21/15% CIPANP%2015%/%Harry%Nelson% 9%

(slide%from%Walter%Pe'us,%spoke%here)%%

Homestake:%

• %LUX/LZ%

Soudan:%

• %CDMS%
• %CoGeNT%

SNOLAB:%

• %DEAP/CLEAN%
• %PICASSO%
• %PICO%
• %DAMIC%
• %SuperCDMS%

Boulby:%

• %DRIFT%

Canfranc:%

• %ANAIS%
• %ArDM%
• %Rosebud%

Modane:%

• %EDELWEISS%

Gran%Sasso:%

• %CRESST%
• %DAMA/LIBRA%
• %DarkSide%
• %XENON%

Kamioka:%

• %XMASS%

YangYang:%

• %KIMS%

JinDPing:%

• %PandaLX%
• %CDEX%

South%Pole:%

• %DMLICE%

ANDES:% (planned)% Stawell:%

• %SABRE%

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KIMS ANAIS SABRE DM-ICE

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10 1 100 1000 104 10 46 10 45 10 44 10 43 10 42 10 41 10 40 10 39 WIMP Mass GeV c2 WIMP- nucleon cross section cm2

CDMS II Ge (2009)

DS-50 (2014)

Xenon100 (2012) C R E S S T CoGeNT (2012) CDMS Si (2013) E D E L W E I S S ( 2 1 1 ) DAMA S I M P L E ( 2 1 2 ) ZEPLIN-III (2012) COUPP (2012) XENON 10 S2 (2013) CDMS-II Ge Low Threshold (2011) LUX (2013) W A R P ( 2 8 ) PICO-2L (2015) SuperCDMS (2014) PICASSO (2012) PANDAX (2014-2015)

ρσ

dρσ dMχ = const.

Mmin ∝ 1 vesc r EthA 2 while background free: ρσ ∝ Mχ MT TA f(Eth, Mχ) where is maximum. f(Eth, Mχ) Mχ

Direct detection

DAMA/LIBRA

NaI scintillating crystals in Gran Sasso

Observe a highly significant (9 σ) annual modulation, consistent with the “model independent DM signal” T = 0.999 ± 0.002 y and maximum ~ June 2nd ± 7 d

2-6 keV Time (day) Residuals (cpd/kg/keV)

DAMA/LIBRA ≈ 250 kg (0.87 ton×yr)

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DMDICE%Experiments%

5/21/15% CIPANP%2015%/%Harry%Nelson% 10%

DM-ICE17

(January 2011 – present)

DM-ICE37

(April 2014 – present)

DM-ICE250

(future)

First dark matter experiment in South Pole ice

• Demonstrated viability

and advantage of environment

R&D testbed for NaI detectors

• Crystal background
• Light yield
• PMT/lightguide

configurations

Science result

• Definitive test of DAMA

dark matter claim

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SABRE%concept%

5/21/15% 11%

NaI%in%Scint.%Veto%

CIPANP%2015%/%Harry%Nelson%

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PICO - Jeter Hall - CIPANP 2015 May 20, 2015 10

PICO-60

! Fill of 37 kg CF3I at SNOLAB completed April 2013 ! Results presented here are preliminary

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PICO - Jeter Hall - CIPANP 2015 May 20, 2015 11

PICO-60

! Large number of background events ! Significant number of events with AP~1, but inconsistent with neutron calibration distributions

! Similar to COUPP4 backgrounds ! Not spatially uniform 0<ln(AP)<0.5& 1<ln(AP)<1.5&

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PICO - Jeter Hall - CIPANP 2015 May 20, 2015 16

PICO-60 implications for DAMA

PRELIMINARY*

! Using DAMA spectrum between 2 and 6 keV ! Applying DAMA iodine quenching factor (0.09) results in expectation

• f 49 recoils above 22 keV

! PICO-60 observes <4.1 events at 90% C.L.

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Model independent demonstration that DAMA signal cannot be Iodine recoils

PICO - Jeter Hall - CIPANP 2015 May 20, 2015 6

PICO-2L

! Filled with 2 liters C3F8 in September 2013 ! Stable operations at SNOLAB from October 2013 to May 2014 resulting in over 250 kg day exposure with thresholds of 3, 6, and 8 keV ! Reincarnation of COUPP4 chamber with substantial improvements and new target

! arXiv 1204.3094; PRD 86, 052001 (2012)

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PICO - Jeter Hall - CIPANP 2015 May 20, 2015 9

PICO-2L results

arXiv:1503.00008, accepted in PRL

WIMP mass [GeV/c2] SD WIMP−proton cross section [cm2]

I c e C u b e (χχ → W +W −) ( χ χ → b b ) Super−K (hard) Super−K (soft) CMS (A−V) PICO 250L C3F8, 3 keV PICO 2L P I C A S S O 2 1 2 SIMPLE 2014 PICO 2L 0 bkg

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1

10

2

10

3

10

4

10

−42

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−41

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−40

10

−39

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−38

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−37

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−36

! Candidate events are inconsistent with WIMP

! KS p-value of 0.04 for timing distribution of events

! Limits are derived

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DarkSide 50

Radon-free clean room Water Cerenkov Detector Liquid scintillator Veto Inner detector TPC

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χ Nuclear Recoil excites and ionizes the noble liquid, producing scintillation light (S1)that is detected by the photomultipliers

S1

Ar

Scintillation light proportional to recoil energy Δt ~ 7 us

TPC for WIMPs: DS50

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e- The ionized electrons that survive recombination are drifted towards the liquid-gas interface by the electric field

Electron Drift Velocity ~ 0.94 mm/us Max Drift Time ~ 373 us

TPC for WIMPs: DS50

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The electrons are extracted into the gas region, where they induce electroluminescence (S2)

S1 S2

The time between the S1 and S2 signals gives the vertical position

Drift Time

Δt ~ 30 us

TPC for WIMPs: DS50

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50% Acceptance, < 0.1 ER Leakage at 102 PE, 47 keVr

]

2

[GeV/c

χ

M 1 10

2

10

3

10

4

10 ]

2

[cm σ

46 −

10

45 −

10

44 −

10

43 −

10

42 −

10

41 −

10

40 −

10

D S

• 5

( 2 1 4 ) W A R P ( 2 7 ) L U X ( 2 1 3 ) X E N O N

• 1

( 2 1 2 ) C D M S ( 2 1 ) P a n d a X

• I

( 2 1 4 )

S1 [PE] 100 150 200 250 300 350 400 450

90

f 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 5000 10000 15000 20000 25000 30000 35000

50% 90%

< 0.01 ER / 5 PE bin S1 > 80 PE < 0.01 ER / 5 PE bin 90% NR Acceptance DM Search Box

DS-50 AAr Result

1.42 ton-day exposure

39Ar

arXiv:1410.0653

S1 [PE] 1000 2000 3000 4000 5000 6000 7000 Events/50 PE/kg/sec

• 6

10

• 5

10

• 4

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• 3

10

• 2

10

• 1

10 AAr (200 V/cm, 44 kg) UAr (200 V/cm, 44 kg) UAr (200 V/cm, 4 kg core) AAr (200 V/cm, 44 kg) UAr (200 V/cm, 44 kg) UAr (200 V/cm, 4 kg core) AAr (200 V/cm, 44 kg) UAr (200 V/cm, 44 kg) UAr (200 V/cm, 4 kg core)

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Underground Argon Core (4 kg) Hint of 39Ar spectra visible

39Ar < 3.3 mBq/kg

> 300x Reduction

39Ar Beta

Spectrum ?

Underground Ar

]

[cm

r 50 100 150 200 250 300 z [cm] 5 10 15 20 25 30 35

20 40 60 80 100 120 140

Previous AAr exposure equivalent to 1.2 ton-years of UAr

• 2

WIMP mass / GeV c 1 10

2

10 WIMP-nucleon cross-section / pb

• 7

10

• 6

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• 5

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• 4

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• 3

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• 2

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• 1

10 1

WIMP 90% exclusion limits

D A M I C ( 2 1 4 ) DAMIC(2012) D A M I C 1 ( 2 1 6 ) SUPERCDMS(2014) CDMSLite(2013) CRESST(2014) CDMSII-Si(2013) LUX(2013) 6 kg d 0.3 kg d 30 kg d Most sensitive for Mχ < 3 GeV c-2 Complementary to Xenon searches

DAMIC

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Charge-coupled devices (CCDs) as low threshold, low background particle detectors. Will directly probe the possible signal in CDMS II-Si. Test setup at SNOLAB already shows great potential.

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SNOLAB installation

VIB Lead block Cu box with CCDs Kapton signal cable Cu vacuum vessel CCD Si support Copper bar Kapton signal cable Poly- ethylene Lead

• J. Zhou

Detector

• Charged particles

produce ionization in CCD bulk. Charge collected by each pixel on CCD plane is read out. 3.62 eV for e-h pair. ~2 e- RMS read-out noise.

• z

x y

• Charge drifted up and held at gates.

z

pixel

x x y σxy σxy

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2080 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

5 4 3 2 1 Energy measured by pixel / keV

Diffusion limited

Particle tracks

6 keV front 6 keV back

5 10 15 20 25 30 Energy measured by pixel / keV 30 25 20 15 10 5

4180 4190 4200 4210 4220

α e μ X-ray? n, WIMP? Diffusion limited 50 pixels

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Front Back

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CCD Performance

>95% of the image good quality.

CCDs are manufactured with very high resistivity silicon: Low radioactive backgrounds. Low dark current (0.01 e- / pix / day). Very few (if any) defects in the silicon lattice.

ee

Energy measured in pixel / eV 50 100 150 200 1 10

2

10

3

10

4

10

5

10

Distribution of pixel values in image 30 ks exposure blank

6.7 eVee RMS noise! 10794 images acquired over 126 days. All good. ±6%

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Energy / keV

1 10

Reconstructed energy / keV

1 10

Calibration data to X-ray lines

C Kα (0.28 keV) O Kα Al Kα Si Kα Ca Kα

55Fe 241Am

60 keV

Energy / keV 1 2 3 4 5 6 7 1 10

2

10

3

10

4

10

5

10 Fe source spectrum in Chicago chamber

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Mn K! Mn K" Cr K! Mn K escape lines Noise Si K! Cl K!

X-rays

/ pixels

xy

σ 0.2 0.4 0.6 0.8 1 1.2 1.4 Energy / keV 5 5.2 5.4 5.6 5.8 6 6.2 6.4 6.6 6.8 7 20 40 60 80 100 120 140 160 180 200

from front and back

α

Mn K

Front Back

E resolution: 53 eV at 5.9 keV from front! Fano = 0.13. Depth reconstruction. σxy = 1.4 z = 675 μm

ee

Energy / keV 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Counts 100 200 300 400 500 600 700

BeO target Al target

Sb source

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Spectrum from

ee

Energy / keV 1 2 3 4 5 6 7 8 9 10 100 200 300 400 500 600 Sb-Al compared to expected Compton background

Sb-Al data =135 keV sim

γ

E

Drop at 150 eVee

ee

Deposited energy / keV 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2 4 6 8 10 12 14

• rays

γ Spectrum from 500 keV

Silicon atom Free electron

4 M-shell e- 6 L-shell p e- 2 K-shell e- 2 L-shell s e- Binding energies

neutrons, γs

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24 keV neutrons from

9Be(γ,n) reaction.

3.2 keVr γ background reveals Compton features near threshold.

Energy / keV 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 m µ Depth / 100 200 300 400 500 600 0.2 0.4 0.6 0.8 1 1.2

1x1, Likelihood

Simulated

ee

Simulated energy / keV 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 m µ Simulated depth / 100 200 300 400 500 600 0.2 0.4 0.6 0.8 1 1.2

• seed

σ Acceptance for 1x100, 3

Simulated energy / keV 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 Acceptance 0.2 0.4 0.6 0.8 1

Acceptances for different acquisition modes

1x100 1x1

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Detection efficiency

Detection efficiency vs. depth

1x1

140 eVee Significant improvement in threshold!

Already acquired some data in SNOLAB.

80 eVee

1x100

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Sequence of βs starting in the same pixel of the CCD in different images.

210Pb 210Bi 210Po

τ1/2 = 5 d 64 keV 1.2 MeV

32Si 32P 32S

τ1/2 = 14 d 0.22 MeV 1.7 MeV

Radioactivity in CCDs

Cluster #79

Δt = 35 days (xo, yo) E1 = 114.5 keV E2 = 328.0 keV

Decay point

32Si - 32P candidate

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β-β coincidences

Search in 57 days of data in 1 CCD:

32Si = 80 kg-1d-1 (95% C.L.)

+110

• 65

210Pb < 33 kg-1d-1 (95% C.L.)

100 kg-1 d-1 of 32Si ~1 dru at low energies. Spatial correlations will allow DAMIC to veto these decays. (limitation for other silicon technologies?)

Cluster distance / pix 2 4 6 8 10 12 14 16 18 20

pairs

N 0.5 1 1.5 2 2.5 3

Data Expected accidentals

/ day

pair

t Δ 10 20 30 40 50 60 70

pairs

N 1 2 3 4 5

Data Expected accidentals

32Si–32P 32Si–32P

(13 events) (6.5 events) (13 events) (6.5 events)

arXiv: 1506.02562

DAMIC100

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We have 24, 16 Mpixel, 675 μm CCDs. Each is 5.5 g. Example in DESI package. New Cu box fits 18 CCDs inside current SNOLAB infrastructure.

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Status at SNOLAB

We have installed DAMIC100 copper box with four 8 MPixel, 675 μm thick CCDs at SNOLAB to study backgrounds.

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Future WIMP searches

SI “High”-mass WIMPs SI “Low”-mass WIMPs SD WIMPs: Increase target mass as much as possible: multi-ton scale Xenon and Argon detectors.

Lowest (~10 eVee) threshold ionization detectors: DAMIC, CDMS-HV Ge. LZ Large C3F8 bubble chamber (PICO 60 /PICO 250).

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Scaling up CCDs

CCD detector technology is quite scalable. Current semiconductor companies can produce 10 cm x 10 cm x 0.1 cm, 20 g CCDs. This box can hold 400 g of Si. A CCD is only read out <5%

• f the time. Multiplexer allows

to read out 20 CCDs with a single controller. This box can be read out with one controller channel.

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Scaling up CCDs

6.4 kg of CCDs can be controlled with 16 channels. Easy cryogenics (100 K). Man power for building + testing at the scale of DECam. Main challenge is background.

• Much progress in dark matter direct detection
• ver past year.
• Ongoing efforts at Fermilab have world-best

limits for SD interactions and low-mass WIMPs.

• DAMIC aims to lead low-mass WIMP searches

for current (DAMIC100) + next generation detectors.

• PICO-60 with C3F8 will lead SD searches.
• SuperCDMS will move to SNOLAB.

Complementary to other technologies.

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Conclusions

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Thank you!

.. and to R. Saldanha, J. Hall and H. Nelson for many of the slides!