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

DAMIC DARK MATTER IN CCD ROMAIN GAIOR 
 (LPNHE PARIS) DARK MATTER DAY (APC 2016/12/01) 1

MOTIVATION → A. Aguilar-Arevalo et al. (DAMIC Collaboration) Phys. Rev. D 94, 082006 DAMIC (2016) Super C D Si HV M S Ge HV D A M I C 1 k g WIMP mass [GeV/c 2 ] 2

THE DAMIC COLLABORATION ➤ FERMILAB ➤ U. Nacional del Sur ➤ U Chicago ➤ Centro Atomico Bariloche ➤ U Michigan ➤ U. Zurich ➤ SNOLAB ➤ LPNHE (Paris 6/7) ➤ UNAM (Mexico) ➤ 11 institutions ➤ FIUNA (Paraguay) ➤ 8 countries ➤ UFRJ (Brasil) ➤ 39 collaborators 3

EXPERIMENTAL METHOD 4

DETECTION PRINCIPLE y CCD coherent elastic scattering x pixel DM Si Si Si electron 3.77eV / e-h pair (T = 130K) holes Si (Si band gap = 1.2eV) nuclear Si Si Si recoil z Si Si Si Si + Light mass target: dR/dE ∝ 1/m A Low noise ~2e- = 7.5 eV —>low E threshold 
 (~ 0.06 keVee) 5

CCD TECHNIQUE PROS AND CONS Pros Cons ➤ low E threshold ➤ 1 detection signal (ionisation) ➤ spatial resolution 
 ➤ timing resolution ~ hours 3D reconstruction ➤ energy resolution ➤ no directionality info ➤ compact and “cheap” detector 6

3D RECONSTRUCTION charge diffusion σ along z axis x muon track z pixel 1615 1610 0 2 4 >6 y y [pix] 1605 Ionization [keV ee ] 1600 1595 1590 1585 x diffusion limited hits diffusion limited hits 1580 σ 1380 1400 1420 1440 1460 x [pix] 55 Fe X rays ➤ Z ∝ σ xy ➤ 3D reconstruction ➤ surface event tagging 7

ENERGY LINEARITY & RESOLUTION 4 10 55 Fe 3 10 K α K β 2 Esc K 10 Si α Esc K β Al 10 1 E [keV] 1 2 3 4 5 6 Calibration data to X-ray lines Energy resolution from X-ray lines Reconstructed energy / keV 241 Am Var(E) / keV 2 Fano = 0.16 10 -2 10 55 Fe Ca-K α Al-K α 10 -3 30eV noise Si-K α 1 O C 1 10 1 10 Energy / keV Energy / keV √ σ = E F E resolution at 5.9 keV: : 54eVee 8

DAMIC CCD ➤ developed at LBNL (Microsystem lab) 
 originally for DECam ➤ Thick CCD: 0.675 mm 0.675 mm ➤ 2.9g (5.8g)/ CCD ➤ 8 (16) MegaPixels ➤ pixel size: 15 x 15 μ m ➤ High resistivity: 10-20 k Ω .cm (low donor density—>fully depleted at 40V) -3 e- /pix /day at 120K) ➤ low dark current (10 9

RADIOGENIC BACKGROUND decay chain ➤ no e ff ective discrimination E = 5.39 MeV E = 6.75 MeV E = 8.66 MeV 1910 504 506 228 Th 216 Po 212 Po 504 504 502 nuclear vs electronic recoil 502 1900 502 500 500 500 498 498 1890 498 496 496 496 494 494 1880 494 ➤ potential bkg from β and γ 492 492 492 490 1870 490 490 488 488 488 60506052 60546056 605860606062 60646066 6050 6052 6054 6056 6058 6060 6062 6064 6066 6048605060526054605660586060606260646066 1860 Δ t = 17.8 d Δ t < 5.5 h 8280 8290 8300 8310 8320 (a) Triple α sequence (b) α – β coincidence ➤ unique spatial and energy resolution ➤ observe decay chain from a single isotope particle identification X-ray? ➤ 238 U and 232 Th decay chain n, WIMP? Diffusion ➤ 32 Si chain limited e α μ 10

READ OUT NOISE blank (taken after exposure 5 10 Image exposure) Blank Gaussian fit 4 10 mean = -0.003 0.001 � Entries per bin � = 1.827 � 0.001 3 10 2 10 10 1 � 10 0 10 20 30 40 - Pixel Value [e ] ➤ noise limited by read out ➤ improved by CDS 
 (Correlated Double Sampling) ➤ limited to 2e- with 
 the current electronics 11

STATUS 12

DAMIC AT SNOLAB Snolab -6 10 ] -1 WIPP/LSBB s -2 Kamioka Muon flux [cm Soudan -7 Y2L 10 Boulby LNGS -8 10 LSM SURF -9 10 SNOLAB Jin-Ping DAMIC -10 10 1 2 3 4 5 6 7 Depth [km w. e.] ➤ 2 km down a mine (6000m water equivalent) ➤ muon rate < 0.27 m -2 d -1 (1 μ /m 2 every 3 days !) 13

DAMIC DETECTOR 14

& CALIBRATION Electronic recoil: 1.08 ) ee X-rays k(E) / k(5.9 keV 1.06 Optical photons ➤ linear response down to 40 eVee 
 1.04 1.02 (e- recoil with X-ray and LED at low 1 0.98 E) 0.96 − 1 10 1 10 ➤ resolution of 54 eVee at 5.9keVee 
 Ionization signal [keV ] ee (Fano factor of 0.133) Ionization efficiency in silicon 10 ee Nuclear recoil: Ionization energy / keV 9 124 UChicago Sb Be Antonella (systematic) Antonella Gerbier et al (1990) ➤ fast neutron source (2-20 keV nr ) 
 Lindhard, k=0.15 Lindhard, k=0.05 1 photoneutron (0.7-2 keV nr ) 
 (Phys. Rev. D 94, 082007) ➤ Deviation from Lindhard model (at -1 10 low E) 1 10 Recoil energy / keV r 15

DAMIC BACKGROUND SPECTRUM v2 pkg outages v3 pkg v4 pkg Pb shield upgrade v1 pkg outages J un13 Sep13 J an13 J an14 Aug14 Dec14 16

ANALYSIS STEPS 5 10 Blanks (noise) 2 Simulated ionization events All data 4 10 1.8 1 × 1 1 × 100 Surface (sim) Data exposures (1 1) � candidates Fit to tail of noise 1.6 Entries per bin 1.4 3 10 1.2 σ xy [pix] 1 2 10 0.8 0.6 we perform a fit to each cluster and record the ∆ LL 10 0.4 1 0.8 0.6 0.4 0.2 0.2 0 3 2 1 0 3 2 -1 1 0 -2 -1 -2 0 -3 -3 1 0 1 2 3 4 5 6 7 8 9 10 0 4 8 12 16 E [keV ee ] Entries � 50 � 45 � 40 � 35 � 30 � 25 � 20 � 15 � 10 � 5 0 LL � 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 17

RESULTS -36 10 WIMP-nucleon cross-section [cm ] This work 2 0.6 kg d -37 10 -38 10 -39 10 CRESST II 2015 - 52 kg d DAMA/Na -40 10 CDMSLite - 70 kg d -41 10 -42 10 LUX - 14 ton d CDMS-II Si - 140 kg d -43 10 1 10 -2 WIMP Mass [GeV c ] ➤ compatible background hypothesis (Compton scatt.) ➤ sensitivity at low mass WIMP ( m χ < 10 GeV/c 2 ) ➤ exclusion of a part of CDMSII signal with same target (Si) 18

STATUS OF OPERATION ➤ 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 19

FUTURE PLANS 20

DAMIC FORESEEN SENSITIVITY DAMIC2016 (0.1e- read out noise) ➤ target mass to kg scale ➤ detector threshold down to ~ 8 eVee (~ 0.3e - ) ➤ background ~ 0.01 d.r.u. 21

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 kg scale DAMIC is feasible with current technology in a short time 22

& & LOWER THE ENERGY THRESHOLD & BACKGROUND ➤ read out noise goal: <0.3e- (w.r.t. 2 now) Digital filtering first amplifier optimisation skipper CCD ➤ radio background goal: 0.01 d.r.u (w.r.t. 5 now) ➤ Use electroformed copper ➤ already one module in test 32 Si background ➤ eventually limited by 23

DAMIC FORESEEN SENSITIVITY DAMIC2016 (0.1e- read out noise) ➤ target mass to kg scale - ) ➤ detector threshold down to ~ 8 eVee (~ 0.3e ➤ background ~ 0.01 d.r.u. 24

CONCLUSION ➤ CCD is an e ffi cient 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 25

THANKS FOR YOUR ATTENTION 26

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

SIGNAL HYPOTHESIS 28

CCD Cu box

Stability

image example

UNDERSTANDING BACKGROUND particle identification decay chain X-ray? E = 5.39 MeV E = 6.75 MeV E = 8.66 MeV 1910 504 506 228 Th 216 Po 212 Po 504 504 502 n, WIMP? 502 1900 502 500 500 500 498 498 1890 498 Diffusion 496 496 496 494 494 1880 494 492 limited e 492 492 490 1870 490 490 488 488 488 60506052 60546056 605860606062 60646066 6050 6052 6054 6056 6058 6060 6062 6064 6066 6048605060526054605660586060606260646066 1860 Δ t = 17.8 d Δ t < 5.5 h 8280 8290 8300 8310 8320 (a) Triple α sequence (b) α – β coincidence α μ ➤ Radiogenic background identification (2015 JINST 10 P08014) ➤ Th and U contamination ➤ 32 Si bkg estimation 32

DM candidate spectrum 3 2.5 ee Events per 100 eV 2 1.5 1 0.5 0 0 1 2 3 4 5 6 7 E [keV ] ee

DAMIC FORESEEN SENSITIVITY WIMP 90% exclusion limits − 35 10 2 WIMP-nucleon cross-section / cm 36 − 10 CDMSLite(2015) − 37 10 DAMIC(2016) 0.6 kg-d − 38 10 39 − 10 DAMA/Na(2009) − 40 10 CRESST(2015) − 41 10 DAMIC100(2017) 30 kg-d 42 − 10 CDMSII-Si(2013) DAMIC1K 300 kg-d − 43 10 0.01 dru, 0.5 e - noise LUX(2015) 44 − 10 1 10 -2 WIMP Mass / GeV c ➤ target mass to kg scale ➤ detector threshold down to ~ 8 eVee (~ 0.3e - ) ➤ background ~ 0.01 d.r.u. 34

COMPARISON OF EXPECTED SENSITIVITY DAMIC2016 DAMIC100 DAMIC1000 35

Electron recoil

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