Dark matter direct detection Alvaro E Chavarria KICP at The University of Chicago 1
Overview • 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
Dark matter • 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. 3
Direct detection Xe Ge Ar Si Ne χ Nucleus on Earth From arXiv:1310.8327v2 [hep-ex] Mass: 100 GeV galactic Recoil halo B.Loer Thesis E χ ∼ M χ c 2 Mass: 1 TeV GeV keV 4
Direct detection • Large target mass many targets. M T • Count for long time . T • Lowest possible threshold , to increase E th fraction of recoil spectrum probed . f • Lowest possible background <1 event kg -1 y -1 : low radioactivity environment, nuclear/electron recoil discrimination. • Large atomic mass increases total rate A (coherent scattering) but increases minimum WIMP mass probed . M min 5
Technologies Scintillators Ionization Noble liquid TPCs DAMA/LIBRA CoGeNT LUX/LZ ANAIS CDMS-HV XENON SABRE CDEX DarkSide DM-Ice DAMIC ArDM KIMS Panda-X Superheated DEAP/CLEAN PICO Phonon + Ionization XMASS CDMS-II Phonon + Scintillation SuperCDMS CRESST EDELWEISS Nuclear recoil discrimination 6
Locations (slide%from%Walter%Pe'us,%spoke%here)%% Soudan:% Boulby:% • %CDMS% • %DRIFT% • %CoGeNT% Modane:% YangYang:% Canfranc:% • %EDELWEISS% • %KIMS% KIMS • %ANAIS% ANAIS • %ArDM% • %Rosebud% Kamioka:% Homestake:% SNOLAB:% Gran%Sasso:% • %XMASS% JinDPing:% • %LUX/LZ% • %DEAP/CLEAN% • %CRESST% • %PandaLX% • %PICASSO% • %DAMA/LIBRA% • %CDEX% • %PICO% • %DarkSide% • %DAMIC% • %XENON% • %SuperCDMS% ANDES:% (planned)% Stawell:% • %SABRE% SABRE South%Pole:% • %DMLI CE % DM-ICE 5/21/15% CIPANP%2015%/%Harry%Nelson% 9% 7
Direct detection XENON 10 S2 (2013) CDMS-II Ge Low Threshold (2011) 10 39 PICASSO CoGeNT WIMP- nucleon cross section cm 2 PICO-2L (2012) (2012) 10 40 (2015) ρσ CDMS Si (2013) ) 2 1 0 2 ( 10 41 E L P M S I COUPP (2012) DAMA SuperCDMS 8 ) 0 0 2 (2014) ( P R ZEPLIN-III (2012) A W C 10 42 R E DS-50 (2014) S S while background free: T ) 1 1 0 2 ( S S E I Xenon100 (2012) 10 43 W L E D E M χ CDMS II Ge (2009) ρσ ∝ 10 44 PANDAX (2014-2015) M T TA f ( E th , M χ ) LUX (2013) d ρσ = const. 10 45 dM χ 10 46 1 10 1000 10 4 100 WIMP Mass GeV c 2 r E th A 1 f ( E th , M χ ) where is maximum. M min ∝ v esc 2 M χ 8
DAMA/LIBRA NaI scintillating crystals in Gran Sasso 2-6 keV Residuals (cpd/kg/keV) DAMA/LIBRA ≈ 250 kg (0.87 ton × yr) Time (day) Observe a highly significant (9 σ ) annual modulation, consistent with the “model independent DM signal” T = 0.999 ± 0.002 y and maximum ~ June 2 nd ± 7 d 9
DMDI CE %Experiments% DM-I CE 17 DM-I CE 37 DM-I CE 250 ( January 2011 – present ) ( April 2014 – present ) ( future ) R&D testbed for NaI First dark matter Science result detectors experiment in South - Definitive test of DAMA dark matter claim - Crystal background Pole ice - Light yield - Demonstrated viability - PMT/lightguide and advantage of configurations environment 5/21/15% CIPANP%2015%/%Harry%Nelson% 10% 10
SABRE%concept% NaI%in%Scint.%Veto% 5/21/15% CIPANP%2015%/%Harry%Nelson% 11% 11
PICO-60 ! Fill of 37 kg CF 3 I at SNOLAB completed April 2013 ! Results presented here are preliminary PICO - Jeter Hall - CIPANP 2015 May 20, 2015 10 12
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 1<ln(AP)<1.5& 0<ln(AP)<0.5& PICO - Jeter Hall - CIPANP 2015 May 20, 2015 11 13
Model independent demonstration that PICO-60 DAMA signal cannot be Iodine recoils implications for DAMA PRELIMINARY* ! Using DAMA spectrum between 2 and 6 keV ! Applying DAMA iodine quenching factor (0.09) results in expectation of 49 recoils above 22 keV ! PICO-60 observes <4.1 events at 90% C.L. PICO - Jeter Hall - CIPANP 2015 May 20, 2015 16 14
PICO-2L ! Filled with 2 liters C 3 F 8 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) ! PICO - Jeter Hall - CIPANP 2015 May 20, 2015 6 15
PICO-2L results arXiv:1503.00008, accepted in PRL − 36 10 ! Candidate events are inconsistent with WIMP 2 1 0 2 O − 37 S 10 S A ) C b SD WIMP − proton cross section [cm 2 ] b I P ! KS p-value of 0.04 for timing → PICO 2L χ Super − K (soft) ( χ distribution of events SIMPLE 2014 − 38 10 PICO 2L ! Limits are derived 0 bkg Super − K (hard) − 39 ( χχ → W + W − ) 10 CMS (A − V) e b u C e c I − 40 10 PICO 250L − 41 10 C 3 F 8 , 3 keV − 42 10 1 2 3 4 10 10 10 10 WIMP mass [GeV/c 2 ] PICO - Jeter Hall - CIPANP 2015 May 20, 2015 9 16
DarkSide 50 Radon-free clean room Water Cerenkov Detector Liquid scintillator Veto Inner detector TPC 17
TPC for WIMPs: DS50 χ Nuclear Recoil excites and ionizes the noble liquid, producing scintillation light (S1)that is detected by the photomultipliers S1 Ar Δ t ~ 7 us Scintillation light proportional to recoil energy 18
TPC for WIMPs: DS50 The ionized electrons that survive recombination are drifted towards e - the liquid-gas interface by the electric field Electron Drift Velocity ~ 0.94 mm/us Max Drift Time ~ 373 us 19
TPC for WIMPs: DS50 The electrons are extracted into the gas region, where they induce electroluminescence (S2) S1 S2 Δ t ~ 30 us Drift Time The time between the S1 and S2 signals gives the vertical position 20
− 40 10 DS-50 AAr ] 2 [cm σ − 41 10 ) 7 0 0 2 ( P R A W Result − 42 10 ) 4 ) 1 0 4 1 2 ( 0 2 ) ( 0 2 5 1 I - 0 S - 2 X D ( a d 0 n 0 a − 43 1 P 10 - N ) O N 0 1 E X 0 2 ( S ) M 3 D 1 C 0 2 ( X U 1.42 ton-day 44 − L 10 − 45 10 exposure arXiv:1410.0653 46 − 10 3 2 4 1 10 10 10 10 2 M [GeV/c ] χ 1 90 f 50% Acceptance, < 0.1 35000 0.9 DM Search Box ER Leakage at 102 PE, 0.8 30000 47 keVr 50% 0.7 25000 90% 0.6 39 Ar 20000 0.5 0.4 15000 < 0.01 ER / 5 PE bin 0.3 10000 0.2 S1 > 80 PE 5000 0.1 < 0.01 ER / 5 PE bin 0 0 90% NR Acceptance 100 150 200 250 300 350 400 450 S1 [PE] 21
Entries 171011 Entries 171011 Underground Ar 35 z [cm] 140 30 120 25 100 20 80 Underground Argon Core (4 kg) 15 60 10 40 Hint of 39 Ar spectra visible 5 20 0 0 0 50 100 150 200 250 300 39 Ar < 3.3 mBq/kg 2 r 2 [cm ] -1 10 Events/50 PE/kg/sec AAr (200 V/cm, 44 kg) AAr (200 V/cm, 44 kg) AAr (200 V/cm, 44 kg) Previous AAr UAr (200 V/cm, 44 kg) UAr (200 V/cm, 44 kg) UAr (200 V/cm, 44 kg) -2 10 UAr (200 V/cm, 4 kg core) UAr (200 V/cm, 4 kg core) UAr (200 V/cm, 4 kg core) exposure > 300x Reduction -3 10 equivalent to 1.2 ton-years of UAr -4 10 39 Ar Beta -5 10 Spectrum ? -6 10 0 1000 2000 3000 4000 5000 6000 7000 S1 [PE] 22
DAMIC Charge-coupled devices (CCDs) as low threshold, low background particle detectors. WIMP 90% exclusion limits 1 WIMP-nucleon cross-section / pb Most sensitive SUPERCDMS(2014) for M χ < 3 GeV c -2 -1 10 0.3 kg d ) 4 1 -2 0 10 2 ( C I M A DAMIC(2012) D Test setup at SNOLAB -3 10 already shows great CDMSII-Si(2013) 6 kg d CDMSLite(2013) potential. -4 10 ) 6 1 0 2 ( 0 0 1 C I M A D -5 10 Will directly probe Complementary to 30 kg d Xenon searches the possible signal in CRESST(2014) -6 10 LUX(2013) CDMS II-Si. -7 10 2 10 1 10 -2 WIMP mass / GeV c 23
SNOLAB installation CCD Poly- Si support VIB ethylene Kapton signal cable Lead Copper Lead block Kapton bar signal cable Cu box with CCDs J. Zhou Cu vacuum vessel 24
Detector y ��� ��������������������������� x ����� �� Charged particles �� �� �� �������� produce ionization ����� �� in CCD bulk. ������� �� �� �� ������ z 3.62 eV for �� �� �� �� e-h pair. � x Charge Charge drifted up and held at gates. collected by y each pixel on CCD plane is pixel z ��������������������� read out. σ xy x ��������������������� ~2 e - RMS read-out noise. σ xy 25
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