DAMIC DARK MATTER IN CCD ROMAIN GAIOR (LPNHE PARIS) DARK MATTER - - PowerPoint PPT Presentation

DAMIC

DARK MATTER IN CCD

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ROMAIN GAIOR 


(LPNHE PARIS)

DARK MATTER DAY (APC 2016/12/01)

MOTIVATION

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→

DAMIC (2016)

WIMP mass [GeV/c2]

Super Si HV D A M I C 1 k g Ge HV C D M S

• A. Aguilar-Arevalo et al. (DAMIC Collaboration) Phys. Rev. D 94, 082006

THE DAMIC COLLABORATION

➤ FERMILAB ➤ U Chicago ➤ U Michigan ➤ SNOLAB ➤ FIUNA (Paraguay) ➤ UFRJ (Brasil) ➤ U. Zurich ➤ LPNHE (Paris 6/7) ➤ UNAM (Mexico) ➤ U. Nacional del Sur ➤ Centro Atomico Bariloche

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➤ 11 institutions ➤ 8 countries ➤ 39 collaborators

EXPERIMENTAL METHOD

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DETECTION PRINCIPLE

CCD

Si + Si Si Si Si Si Si Si Si Si

DM

electron holes

pixel

nuclear recoil

coherent elastic scattering

z x y

3.77eV / e-h pair (T = 130K)

(Si band gap = 1.2eV)

Light mass target: dR/dE ∝ 1/mA

Low noise ~2e- = 7.5 eV —>low E threshold 
 (~ 0.06 keVee)

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CCD TECHNIQUE PROS AND CONS

Pros

➤ low E threshold ➤ spatial resolution 


3D reconstruction

➤ energy resolution ➤ compact and “cheap”

detector

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Cons

➤ 1 detection signal

(ionisation)

➤ timing resolution ~ hours ➤ no directionality info

3D RECONSTRUCTION

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diffusion limited hits

z

pixel

x

➤ Z ∝ σxy ➤ 3D reconstruction ➤ surface event tagging

charge diffusion σ along z axis

diffusion limited hits

x y σ

x [pix] 1380 1400 1420 1440 1460 y [pix] 1580 1585 1590 1595 1600 1605 1610 1615 Ionization [keVee] >6 2 4

muon track

55Fe X rays

ENERGY LINEARITY & RESOLUTION

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Energy / keV

1 10

Reconstructed energy / keV

1 10 Calibration data to X-ray lines

C O Al-Kα Si-Kα Ca-Kα

55Fe 241Am

Energy / keV

1 10

Var(E) / keV2

10-3 10-2 Energy resolution from X-ray lines

30eV noise Fano = 0.16

E [keV] 1 2 3 4 5 6 1 10

2

10

3

10

4

10

Al Si

Esc K

Esc K

K Kβ 55Fe

E resolution at 5.9 keV: : 54eVee

σ = √ EF

DAMIC CCD

➤ developed at LBNL (Microsystem lab)


• riginally for DECam

➤ Thick CCD: 0.675 mm ➤ 2.9g (5.8g)/ CCD ➤ 8 (16) MegaPixels ➤ pixel size: 15 x 15 μm ➤ High resistivity: 10-20 kΩ.cm (low donor

density—>fully depleted at 40V)

➤ low dark current (10

• 3 e- /pix /day at 120K)

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0.675 mm

RADIOGENIC BACKGROUND

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α

e

μ

X-ray? n, WIMP?

Diffusion

limited

➤ no effective discrimination

nuclear vs electronic recoil

➤ potential bkg from β and γ

particle identification decay chain

➤ unique spatial and energy resolution ➤ observe decay chain from a

single isotope

➤ 238U and

232Th decay chain

➤ 32Si chain

READ OUT NOISE

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➤ noise limited by read out ➤ improved by CDS 


(Correlated Double Sampling)

➤ limited to 2e- with 


the current electronics

• Pixel Value [e ]

• 10

0.001

• = 1.827
• 0.001
• mean = -0.003

blank (taken after exposure) exposure

STATUS

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DAMIC AT SNOLAB

DAMIC Snolab

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➤ 2 km down a mine (6000m water equivalent) ➤ muon rate < 0.27 m-2 d-1 (1μ /m2 every 3 days !)

Depth [km w. e.] 1 2 3 4 5 6 7 ]

• 1

s

• 2

Muon flux [cm

• 10

10

• 9

10

• 8

10

• 7

10

• 6

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WIPP/LSBB Kamioka Soudan Y2L Boulby LNGS LSM SURF SNOLAB Jin-Ping

DAMIC DETECTOR

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CALIBRATION

]

Ionization signal [keV

10 1 10 )

k(E) / k(5.9 keV 0.96 0.98 1 1.02 1.04 1.06 1.08

X-rays Optical photons

Electronic recoil:

➤ linear response down to 40 eVee


(e- recoil with X-ray and LED at low E)

➤ resolution of 54 eVee at 5.9keVee


(Fano factor of 0.133) Nuclear recoil:

➤ fast neutron source (2-20 keVnr)


photoneutron (0.7-2 keVnr)


(Phys. Rev. D 94, 082007)

➤ Deviation from Lindhard model (at

low E)

&

• 1

Ionization efficiency in silicon

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DAMIC BACKGROUND SPECTRUM

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• utages
• utages

ANALYSIS STEPS

LL

• 50
• 45
• 40
• 35
• 30
• 25
• 20
• 15
• 10
• 5
• Entries per bin

1 10

10

10

10

10

Blanks (noise) Simulated ionization events 1)

• Data exposures (1

Fit to tail of noise

• 1. data selection (E < 10 keVee, noisy pixel)
• 2. find hits with LL clustering algo. (comparison bkg vs bkg+signal)
• 3. exclusion of surface events
• 4. fit of the candidate spectrum
• 3
• 2
• 1

• 3
• 2
• 1

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RESULTS

➤ compatible background hypothesis (Compton scatt.) ➤ sensitivity at low mass WIMP ( mχ< 10 GeV/c2) ➤ exclusion of a part of CDMSII signal with same target (Si)

• 2

WIMP Mass [GeV c ] 1 10

WIMP-nucleon cross-section [cm ]

• 43

10

• 42

10

• 41

10

• 40

10

• 39

10

• 38

10

• 37

10

• 36

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CDMS-II Si - 140 kg d CDMSLite - 70 kg d DAMA/Na LUX - 14 ton d CRESST II 2015 - 52 kg d

0.6 kg d This work

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STATUS OF OPERATION

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➤ April 2016: installation of 6 new CCDs (8 total) ➤ replaced copper box and modules ➤ replacement of parts of the shielding with

ancient lead (Roman lead from Modane)

➤ cleaning and etching ➤ Issues appeared on 2 CCDs ➤ Tests/fix at Fermilab since then ➤ due to mechanical stress ➤ 10 CCDs (~60g) to be installed in January 2017

FUTURE PLANS

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DAMIC2016

DAMIC FORESEEN SENSITIVITY

➤ target mass to kg scale ➤ detector threshold down to ~8 eVee (~ 0.3e-) ➤ background ~ 0.01 d.r.u.

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(0.1e- read out noise)

INCREASE MASS

➤ current mass: 5.8g /CCD (DAMIC100=>18CCDs) ➤ goal: increase CCD mass 3X (DAMIC1000=>~50CCDs) ➤ ~1mm with same fabrication process


~ few mm with new fabrication process (dev. at U. Chicago)

➤ larger format :4k x 4x —> 6k x 6k

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kg scale DAMIC is feasible with current technology in a short time

LOWER THE ENERGY THRESHOLD & BACKGROUND

➤ read out noise goal: <0.3e- (w.r.t. 2 now)

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first amplifier optimisation skipper CCD Digital filtering

➤ radio background goal: 0.01 d.r.u (w.r.t. 5 now)

➤ Use electroformed copper ➤ already one module in test ➤ eventually limited by

32Si background

DAMIC2016

DAMIC FORESEEN SENSITIVITY

➤ target mass to kg scale ➤ detector threshold down to ~8 eVee (~ 0.3e

• )

➤ background ~ 0.01 d.r.u.

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(0.1e- read out noise)

CONCLUSION

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➤ CCD is an efficient DM detector for low mass WIMP ➤ stable operation ➤ very good energy & spatial resolution ➤ After a phase of development / bkg reduction DAMIC has released

competitive limits

➤ Currently upgrading to DAMIC100 ➤ Development for DAMIC1KG: ➤ electronics to reduce readout noise ➤ CCD fabrication to increase the mass

THANKS FOR YOUR ATTENTION

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CCD

CCD Wire bonds Clocks, Bias, and Signal cable Copper frame 6 cm

SIGNAL HYPOTHESIS

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CCD

Cu box

Stability

image example

UNDERSTANDING BACKGROUND

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α

e

μ

X-ray? n, WIMP?

Diffusion

limited ➤ Radiogenic background identification (2015 JINST 10 P08014) ➤ Th and U contamination ➤ 32Si bkg estimation

particle identification decay chain

DM candidate spectrum

ee

E [keV ] 1 2 3 4 5 6 7

ee

Events per 100 eV 0.5 1 1.5 2 2.5 3

DAMIC FORESEEN SENSITIVITY

• 2

WIMP Mass / GeV c 1 10

WIMP-nucleon cross-section / cm

10

10

10

10

10

10

10

10

10

10

WIMP 90% exclusion limits

DAMA/Na(2009) CDMSII-Si(2013) LUX(2015) CRESST(2015) CDMSLite(2015) DAMIC(2016) 0.6 kg-d DAMIC100(2017) 30 kg-d DAMIC1K 300 kg-d 0.01 dru, 0.5 e- noise

➤ target mass to kg scale ➤ detector threshold down to ~8 eVee (~ 0.3e-) ➤ background ~ 0.01 d.r.u.

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COMPARISON OF EXPECTED SENSITIVITY

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DAMIC2016 DAMIC100 DAMIC1000

Electron recoil

Axion like particle

DAMIC1K Axion models DAMIC100(2017) Red giant CoGeNT(2008) XENON100(2014) KSVZ DFSZ (also millicharged particles)