DAMIC at SNOLAB Alvaro E Chavarria University of Chicago for the - - PowerPoint PPT Presentation
DAMIC at SNOLAB Alvaro E Chavarria University of Chicago for the DAMIC Collaboration 1 Outline Charge coupled devices (CCDs) as detectors for low-energy particles. Characterization of the DAMIC devices. DAMIC installation at SNOLAB.
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Alvaro E Chavarria University of Chicago for the DAMIC Collaboration
for low-energy particles.
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Device is “exposed,” collecting charge until user commands readout.
±
Ionizing particle Free charge carriers Fully depleted substrate
Pixel array
15 µm 675 µm
z x x z y σxy σxy ~ z
Readout can be slow / non-destructive : very low noise (few e-). Silicon band-gap: 1.2 eV. Mean energy for 1 e-h pair: 3.8 eV.
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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
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
X-ray? n, WIMP? Diffusion limited 50 pixels Front Back
DAMIC CCD: 15x15 µm2 pixels
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20 30 40 Entries per bin 1 10
210
310
410
510
0.001
Image Blank Gaussian fit
]
ee
Ionization signal [keV
1 −
10 1 10 )
ee
k(E) / k(5.9 keV 0.96 0.98 1 1.02 1.04 1.06 1.08
X-rays Optical photons
White readout noise <2 e- RMS ~ 7 eVee Linearity demonstrated for signals <10 e-.
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Characterization of Compton background at low energies
Si K-shell Si L-shell
arXiv:1706.06053
]
nr
[keV
r
E
1 10
]
ee
[keV
e
E
1 −
10 1 10
Dougherty (1992) Gerbier et al. (1990) Zecher et al. (1990) Be (2016)
9Sb-
124Antonella (2017) Lindhard, k=0.15
/ ndf
2
0.74 (0.06)
f 0.01
(0.3)
f 0.02
f(3.2) 0.02
y offset 1.0
]
ee
[keV
e
E
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
]
)
ee
Number of nuclear recoils [(10 eV
200 400 600 800 1000
142 / 154
Best-fit with Monte Carlo spectrum Data - full BeO
PRD94 082007 JINST12 P06014
CCD Lead shielding
3He counter
Source Vacuum chamber a) Cross-section of setup BeO base BeO cylinder BeO cap Table Table Activated antimony rod b) 124Sb-9Be source detail 20 cm 2.75 cm
24 keV neutrons from
9Be(γ,n)
reaction
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Single-recoil spectrum very similar to signal from 3 GeV WIMP. End-point = 3.2 keVr
Calibration down to 60 eVee.
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16 Mpix CCD Copper module Kapton signal cable Poly- ethylene Lead
6 cm 5.8 g VIB Lead block Cu box with CCDs Kapton signal cable Cu vacuum vessel
Recoil spectrum in Si target
2 4 6 8 10 1 3 5 7 9 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 E [keVee] σxy [pix]
1×1 1×100 Surface (sim)
4 8 12 16 Entries
All data candidates
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Elastic scattering
silicon nuclei.
2D Gaussian distribution of free charge on pixel array.
Measure E and σxy for every event.
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0.6 kg days of data with test devices at SNOLAB. ~30 dru total background.
WIMP Mass [GeV c ] 1 10
2
WIMP-nucleon cross-section [cm ]
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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
PRD94 082006
eeE [keV ] 1 2 3 4 5 6 7
eeEvents per 100 eV 0.5 1 1.5 2 2.5 3
Observed spectrum in fiducial region
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eeE [keV 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 Detection efficiency 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
1) × Signal (1 100) × Signal (1 1) × Background (1 100) × Background (1
Spectrum consistent with Compton scattered electrons in fiducial region: No WIMP signal.
photon dark matter.
~1 week of data with 1 CCD. Leakage current 4 e- mm-2 d-1. Pixel distribution consistent with white noise + uniform leakage current.
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Hidden Photon Ionization
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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
Cluster #79
Δt = 35 days (xo, yo) E1 = 114.5 keV E2 = 328.0 keV
Decay point
32Si - 32P candidate 32Si = 80 kg-1d-1
(95% C.L.)
+110
210Pb < 37 kg-1d-1
(95% C.L.) 57 days of data in 1 CCD:
JINST 10 P08014
background rate. Analysis ongoing.
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Silicon wafer
DAMIC100 4k x 4k
6k x 6k pixels, 1 mm thick ≈ 20 g / CCD ≈ 50 CCDs / 1 Kg
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LDRD at Fermilab (PI Tiffenberg): Skipper CCDs (LBNL design) successfully tested with sub e- noise. X-ray spectroscopy demonstrated.
Technology will allow 2 e- (few eV) threshold.
Non destructive “skipper” readout: Perform N uncorrelated measurements of the same pixel. Noise decreases by ~1/√N. Measure ΔV N times. ΔV
Reference Signal
arXiv:1706.00028
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[GeV]
χ
m 1 10
2
WIMP-nucleon cross-section / cm
44 −
10
43 −
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42 −
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41 −
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40 −
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39 −
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38 −
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37 −
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36 −
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35 −
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DM-nucleus SI coherent scattering
DAMIC1K(2020) 1 kg-y 0.1 dru, 2 e- thres. D A M I C 1 ( 2 1 7 ) 1 3 k g
D A M I C ( 2 1 6 ) . 6 k g
CDMSII-Si (2013) LUX(2015) CDMSLite(2015) 70 kg-d CRESST(2015) 52 kg-d
σn [cm2]
Also best limits for absorption of hidden photon dark matter.
DM-e Scattering via Ultra-light Hidden Photon
[ ] ] 100 g y, 5 dru, 2e- threshold DAMIC-1K - 1 kg y (2020)
JHEP05(2016)046
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DM-e Scattering via heavy Hidden Photon
DAMIC-1K - 1 kg y (2020)
[ ]
=
]
JHEP05(2016)046
mA0 > 2Mχ
χ χ
A’
✏
gD
e e− e− p p
Direct search: Accelerators: Look for electron’s missing momentum (LDMX) or χ interacting directly (BDX). Ionization produced by dark matter - electron / nucleus scattering.
detectors whose response to ionizing radiation has been thoroughly characterized.
results (WIMPs + hidden photons) with early R&D data.
and suppress backgrounds (esp. dominant 32Si).
CCDs for a 1 kg detector with 2 e- threshold to search for low-mass dark matter by DM-nucleon and DM-electron scattering.
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