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 From on Earth arXiv:1310.8327v2 [hep-ex] galactic Recoil Mass: 100 GeV halo
B.Loer Thesis
M c2 E keV Mass: 1 TeV ⇠ GeV
4 Direct detection • Large target mass M T many targets. • Count for long time T . • Lowest possible threshold E th , to increase 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 A increases total rate (coherent scattering) but increases minimum WIMP mass probed M min . 5 Technologies Noble liquid TPCs Scintillators Ionization LUX/LZ DAMA/LIBRA CoGeNT XENON ANAIS CDMS-HV DarkSide SABRE CDEX ArDM DM-Ice DAMIC Panda-X KIMS DEAP/CLEAN Superheated Phonon + Ionization XMASS PICO CDMS-II Phonon + Scintillation SuperCDMS CRESST EDELWEISS Nuclear recoil discrimination 6 4%New%NaI%Experiments% (slide%from%Walter%LocationsPe'us,%spoke%here)%% Soudan:% Boulby:% •%CDMS% •%DRIFT% •% CoGeNT% Modane:% Canfranc:% YangYang:% •%EDELWEISS% •%KIMS% KIMS •%ANAIS% ANAIS •% ArDM% •%Rosebud% Kamioka:% Homestake:% SNOLAB:% Gran%Sasso:% •%XMASS% •%LUX/LZ% •%DEAP/CLEAN% •%CRESST% JinDPing:% •%PICASSO% •%DAMA/LIBRA% •%PandaLX% •%PICO% •% DarkSide% •%CDEX% •%DAMIC% •%XENON% •% SuperCDMS% ANDES:% (planned)% Stawell:% SABRE•% SABRE%
South%Pole:% •DM-ICE% DMLICE% 5/21/15% CIPANP%2015%/%Harry%Nelson% 9%
7 Direct detection XENON 10 S2 (2013) 10 39 CDMS-II Ge Low Threshold (2011) PICASSO 2 CoGeNT (2012) 40 PICO-2L (2012) cm 10 (2015) CDMS Si (2013) 10 ρσ 41 SuperCDMS DAMA SIMPLE (2012) section (2014) COUPP (2012) 42 CRESST WARP (2008) 10 ZEPLIN-III (2012) cross while background free: DS-50 (2014) 43 10 EDELWEISS (2011) M Xenon100 (2012) CDMS II Ge (2009) ⇢ nucleon 10 44
/ MT TA f(Eth,M ) PANDAX (2014-2015) LUX (2013) d⇢ 45 10
WIMP- = const. dM
10 46 1 10 100 1000 104 WIMP Mass GeV c2 1 EthA f(E ,M ) Mmin where th is maximum. / vesc 2 r M 8 3. Annual Modulation
2-4 keV Signal Modulation DAMA/LIBRA ≈ 250 kg (0.87 ton×yr) Baryons - Baryons travelorbit together ‘together’ in roughly circular orbitsroughly with smallcircular velocity orbits dispersion DM Stars small velocity dispersion
Residuals (cpd/kg/keV) - Dark matter particles travel individually with no circularHalo dependence DM and large velocity dispersion Time (day) 2-5 keV orbit ‘individually’ 0 km/s 220 km/s DAMA/LIBRA ≈ 250 kg (0.87 tonno×yr) circular preference large velocity dispersion Vθ (at out galactic radius)
- As a result, the flux of WIMPs DAMA/LIBRA passing through Earth modulate over the course of a year as Earth Residuals (cpd/kg/keV) NaI scintillating rotates around the sun. Time (day) crystals in Gran Sasso 2-6 keV
DAMA/LIBRA ≈ 250 kg (0.87 ton×yr) 9/10/2013 - TAUP 2013 - Jodi Cooley 30 Residuals (cpd/kg/keV)
Time (day) Observe a highly significant (9 σ) annual modulation, Figure 1: Experimentalconsistent model-independent with the “model residual independent rate of theDMsingle-hit signal”scintillation events, measuredT = by0.999 DAMA/LIBRA,1,2,3,4,5,6 ± 0.002 y and maximum in the ~ (2 June – 4), 2nd (2 ± – 7 5) d and (2 – 6) keV energy intervals as a function of the time. The zero of the time scale is January 1st of the first year of data taking of the9 former DAMA/NaI experiment [15]. The experimental points present the errors as vertical bars and the associated time bin width as horizontal bars. The superimposed curves are the cosinusoidal functions 2π behaviors A cos ω(t − t0) with a period T = ω = 1 yr, with a phase t0 =152.5day (June 2nd) and with modulation amplitudes, A, equal to the central values obtained by best fit over the whole data including also the exposure previously collected by the former DAMA/NaI experiment: cumulative exposure is 1.17 ton × yr (see also ref. [15] and refs. therein). The dashed vertical lines correspond to the maximum expected for the DM signal (June 2nd), while the dotted vertical lines correspond to the minimum. See text.
5 DMDICE%Experiments%
DM-ICE17 DM-ICE37 DM-ICE250 (January 2011 – present) (April 2014 – present) (future)
First dark matter R&D testbed for NaI Science result experiment in South detectors - Definitive test of DAMA Pole ice - Crystal background dark matter claim - Demonstrated viability - Light yield and advantage of - PMT/lightguide environment configurations 5/21/15% CIPANP%2015%/%Harry%Nelson% 10%
10 172 Emily Shields et al. / Physics Procedia 61 ( 2015 ) 169 – 178
Fig. 4. Design for the SABRE experimental setup for one small (1-2 kg) crystal. Opposite faces of the crystal will be coupled to two 3” PMTs operated in coincidence. The PMT pair and crystal will be enclosed in an air-tight enclosure, which will be suspended in a liquid scintillator veto detector currently under construction.SABRE%concept% This detector will be outfitted with 10 8” R5912 Hamamatsu PMTs to detect the scintillation light. The scintillation detector will be surrounded in turn with lead and steel passive shielding.
Fig. 5. Left: Design of the SABRE experimental setup. The liquid scintillator vessel is a φ1.5 m 1.5 m stainless steel cylinder × containing 2 tons ofNaI liquid%in% scintillatorScint (in blue)..%Veto% The NaI(Tl) detectors (in brown) are installed in the center of the veto vessel, and 10 ∼ Hamamatsu 8” PMTs are used to collect the veto scintillation light. The whole setup is shielded from external backgrounds by 20- ∼ 25 cm of passive shielding (in dark gray). Right: An illustration of the DarkSide-50 experiment. A φ4 m liquid scintillator detector (the sphere in the center) is contained inside a φ11 m 10 m water tank, which hosts the DarkSide-50 experiment. The SABRE NaI(Tl) 5/21/15% × CIPANP%2015%/%Harry%Nelson% 11% crystal detectors can be installed between the DarkSide-50 TPC and the walls of the veto sphere. DarkSide-50 also has a number of facilities already in place, such as scintillator handling and purification systems, which can be shared with SABRE. 11 crystals. The second phase will be to conduct a dark matter measurement with 50-60 kg of target material in an underground setting, such as LNGS or SNOLab. PICO-60
! Fill of 37 kg CF3I 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 PICO - Jeter Hall - CIPANP 2015 May 20, 2015 11 13 PICO-60 Model independent demonstration that implications for DAMADAMA signal cannot be Iodine recoils 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 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) PICO - Jeter Hall - CIPANP 2015 May 20, 2015 6 15 PICO-2L results arXiv:1503.00008, accepted in PRL −36 ! Candidate events are 10 inconsistent with WIMP −37 ] 10 ) 2 b PICASSO 2012 b χ ! KS p-value of 0.04 for timing (χ → SIMPLE 2014 −K (soft) PICO 2L −38 distribution of events 10 Super PICO 2L ! Limits are derived 0 bkg −39 −K (hard) 10 − ) Super + W CMS (A−V) W χ (χ → −40 IceCube proton cross section [cm 10 − −41 10 PICO 250L , 3 keV SD WIMP F 8 C 3 −42 10 1 2 3 4 10 10 10 10 WIMP mass [GeV/c2] 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 Nuclear Recoil excites and ionizes the noble liquid, producing scintillation light (S1)that is detected by the photomultipliers χ Ar S1 Δt ~ 7 us Scintillation light proportional to recoil energy 18 TPC for WIMPs: DS50 The ionized electrons that survive e- recombination are drifted towards 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 Δt ~ 30 us Drift Time The time between the S1 and S2 signals gives the vertical position 20 −40 ] 10 2 [cm 41 σ 10− WARP (2007) DS-50 AAr −42 10 DS-50 (2014) 10−43 PandaX-I (2014) Result XENON-100 (2012) CDMS (2010) 10−44 LUX (2013) 1.42 ton-day −45 10 arXiv:1410.0653 exposure 10−46 1 10 102 103 104 2 M χ [GeV/c ] 1 90 f 35000 0.9 50% Acceptance, < 0.1 DM Search Box 0.8 30000 ER Leakage at 102 PE, 50% 0.7 47 keVr 90% 25000 0.6 39 20000 0.5 Ar 0.4 15000 < 0.01 ER / 5 PE bin 0.3 10000 0.2 5000 S1 > 80 PE 0.1 < 0.01 ER / 5 PE bin 0 0 100 150 200 250 300 350 400 450 90% NR Acceptance S1 [PE] 21 Entries 171011 35 140 30 z [cm] 120 25 Underground Ar 100 20 80 15 60 10 Underground Argon Core (4 kg) 40 Hint of 39Ar spectra visible 5 20 0 0 0 50 100 150 200 250 300 39Ar < 3.3 mBq/kg r2 [cm2] 10-1 AAr (200 V/cm, 44 kg) UAr (200 V/cm, 44 kg) 10-2 UAr (200 V/cm, 4 kg core) Previous AAr -3 exposure 10 > 300x Reduction Events/50 PE/kg/sec equivalent to 1.2 -4 10 ton-years of UAr 39 10-5 Ar Beta Spectrum ? 10-6 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 -1 SUPERCDMS(2014) -2 10 Most sensitive < 3 GeV c for Mχ 10-2 0.3 kg d DAMIC(2012) DAMIC(2014) Test setup at SNOLAB 10-3 CDMSII-Si(2013) already shows great 6 kg d 10-4 CDMSLite(2013) potential. DAMIC100(2016) 10-5 Complementary to 30 kg d Will directly probe Xenon searches 10-6 CRESST(2014) WIMP-nucleon cross-section / pb LUX(2013) the possible signal in 10-7 1 10 102 CDMS II-Si. WIMP mass / GeV c-2 23 SNOLAB installation 2 km of rock CCD Poly- Si support VIB Polyethyleneethylene Kapton signal cable Lead Pb Copper Lead block V bar Kapton e signal cable s Cu box s with CCDs 42 21 e cm cm l J. Zhou Cu vacuum vessel 24 y Detector x