Direct detection: results from liquid noble-gas experiments

Transcription

1 Direct detection: results from liquid noble-gas experiments Teresa Marrodán Undagoitia Heidelberg, April 5th, 2018 Teresa Marrodán Undagoitia (MPIK) Liquid noble gases Heidelberg, April / 29

2 How can we look for dark matter? Indirect detection Direct detection Production at LHC χχ γγ, qq,... χn χn p + p χχ + X Teresa Marrodán Undagoitia (MPIK) Liquid noble gases Heidelberg, April / 29

3 Expected interaction rates in a detector WIMP dr de (E, t) = ρ 0 m χ m A v f (v, t) dσ de (E, v) d3 v E R O(10 kev) Astrophysical parameters: ρ 0 = local dark matter density in the Milky Way Standard value: ρ χ 0.3 GeV/cm 3 f (v, t) = WIMP velocity distribution, v 220 km/s Parameters of interest: m χ = WIMP mass ( 100 GeV) σ = WIMP-nucleus elastic scattering cross section Figure from NASA Teresa Marrodán Undagoitia (MPIK) Liquid noble gases Heidelberg, April / 29

4 Direct detection experiments J. Phys. G: 43 (2016) 1, arxiv: Only a selection of liquid noble-gas experiments are presented in this talk! Teresa Marrodán Undagoitia (MPIK) Liquid noble gases Heidelberg, April / 29

5 Advantages of liquid noble gases for DM searches Large masses and homogeneous targets (LNe, LAr & LXe) Two detector concepts: single & double phase 3D position reconstruction fiducialization Transparent to their own scintillation light J. Phys. G: 43 (2016) 1, arxiv: LNe LAr LXe Z (A) 10 (20) 18 (40) 54 (131) Density [g/cm 3 ] Scintillation λ 78 nm 125 nm 178 nm BP [K] at 1 atm Ioniz. [e /kev]* Scint. [γ/kev]* * for electronic recoils Teresa Marrodán Undagoitia (MPIK) Liquid noble gases Heidelberg, April / 29

6 Backgrounds and reduction strategies External γ s from natural radioactivity: Material screening and selection Suppression via self-shielding of the target Rejection of multiple scatters & discrimination Internal contamination: 85 Kr: removal by cryogenic distillation/chromatography/centrifuges 222 Rn: removal using adsorption/distillation and 220 Rn Argon: 39 Ar (565 kev endpoint, 1 Bq/kg), 42 Ar Xenon: 136 Xe ββ decay (T 1/2 = y) long lifetime! External neutrons: muon-induced, (α, n) and from fission reactions Go underground! Shield: passive (polyethylene) or active (water/scintillator vetoes) material selection for low U and Th contaminations Teresa Marrodán Undagoitia (MPIK) Liquid noble gases Heidelberg, April / 29

7 Single phase (liquid) detectors High light yield using 4π photosensor coverage Position resolution in the cm range Pulse shape discrimination (PSD) from scintillation Scintillation decay constants of argon measured by ArDM Very different singlet and triplet lifetimes in argon & neon Relative amplitudes depend on particle type discrimination DEAP-I obtained 10 8 discrimination in LAr above 25 kev ee (50% acceptance) M. G. Boulay et al., arxiv: PSD less powerful in LXe: similar decay constants XMASS, NIM. A659 (2011) 161 Teresa Marrodán Undagoitia (MPIK) Liquid noble gases Heidelberg, April / 29

8 Single phase: DEAP experiment DEAP - LAr detector at SNOLAB, Canada Dark matter Experiment with Argon and Pulse shape discrimination I I I I kg total mass 2-inch thick ultraclean acrylic vessel Wavelength-shifter inside the vessel Light guides to the PMTs First publication with 4.4 d and kg fiducial mass Data from August 2016, arxiv: From Shawn UCLA 2018 conference Teresa Marrodán Undagoitia (MPIK) Liquid noble gases Heidelberg, April / 29

9 Latest DEAP results and status Figures from arxiv: Most sensitive LAr dark matter detector running Next steps About a year of data, working on a second data release Target: 3 tonne year exposure Next generation detector: joining DarkSide-20k Teresa Marrodán Undagoitia (MPIK) Liquid noble gases Heidelberg, April / 29

10 Single phase: XMASS experiment Figure from XMASS 2018, arxiv: XMASS - LXe detector at Kamioka, Japan 1 ton total LXe mass & 800 kg FV Ultra-clean PMTs directly in contact with the LXe target High light yield measured: 14.7 PE/keVee, E th = 0.3 kev ee Recent improved analysis (arxiv: ) Teresa Marrodán Undagoitia (MPIK) Liquid noble gases Heidelberg, April / 29

11 Annual modulation studies DAMA experiment: ultra radio-pure NaI crystals Annual modulation of the background rate in the energy region (2 6) kev very recent data update 12.9 σ combined significance! Talk at LNGS scientific committee meeting (March 26th, 2018) by R. Bernabei Exclusion of the leptophilic interpretation of this signal: 3 σ by the recent XMASS result, arxiv: σ by XENON100 4 y study, PRL 118, (2017) & arxiv: Teresa Marrodán Undagoitia (MPIK) Liquid noble gases Heidelberg, April / 29

12 Two phase noble gas TPC Scintillation signal (S1) Charges drift to the liquid-gas surface Proportional signal (S2) Electron- /nuclear recoil discrimination Drift field Electronegative purity Position resolution Teresa Marrodán Undagoitia (MPIK) Liquid noble gases Heidelberg, April / 29

13 Dual phase LAr & LXe experiments Example using calibration data from the XENON100 detector Teresa Marrodán Undagoitia (MPIK) Liquid noble gases Heidelberg, April / 29

14 The DarkSide-50 LAr double-phase TPC Detector in Hall C at LNGS (Italy) 50 kg depleted argon from underground sources 1400 reduction factor in 39 Ar level Pulse shape for particle discrimination, separation > 10 7 Recent low-mass dark matter result: arxiv: Using charge signal only Energy threshold at 4 e, equivalent to 0.1 kev ee Teresa Marrodán Undagoitia (MPIK) Liquid noble gases Heidelberg, April / 29

15 DarkSide-20k & future liquid argon program 30 t total and 20 t fiducial (arxiv: ) Development of a plant to extract large amounts of argon from underground + isotopic separation ( 39 Ar from 40 Ar) via cryogenic distillation Use of SiPM for light read-out (14 m 2 ) Global argon dark matter collaboration ArDM + DarkSide + DEAP + MiniCLEAN Next step: DarkSide-20k at LNGS (2021 -) Last step: 300 t detector location tbd (2027 -) From C. Galbiati UCLA 2018 conference Teresa Marrodán Undagoitia (MPIK) Liquid noble gases Heidelberg, April / 29

16 The liquid xenon TPC competition LUX: XENON1T: 100 kg fiducial mass (370 kg total) 1.3 t LXe fiducial mass (3.2 t total) Latest results 2016 PRL 118, (2017) Largest existing detector 54 ton day exposure 33.5 ton day exposure Currently running First results 33.6 ton day Decommissioned PANDAX-II: 580 kg fiducial mass (1.2 t total) Latest results 2017 PRL 119, (2017) PRL 119 (2017) Teresa Marrodán Undagoitia (MPIK) Liquid noble gases New results soon! Heidelberg, April / 29

17 LZ: The LUX-ZEPLIN detector Infrastructure and TPC fabrication underway Installation underground in 2019 First data expected in 2020 arxiv: Teresa Marrodán Undagoitia (MPIK) Liquid noble gases Heidelberg, April / 29

18 XENON1T Laboratori Nazionali del Gran Sasso (Italy) below m.w.e. shielding Currently taking data: XENON1T using 2 ton active mass, EPJC 77 (2017) 12, 881 Future: XENONnT with 6 ton active mass Teresa Marrodán Undagoitia (MPIK) Liquid noble gases Heidelberg, April / 29

19 Results and current data SR0: 34.2 live days acquired published XENON1T, PRL 119 (2017) (New PandaX-II result is missing here) SR1: 247 additional live days, analysis being finalized Using 1.3 t fiducial volume Teresa Marrodán Undagoitia (MPIK) Liquid noble gases Heidelberg, April / 29

20 Upgrade to XENONnT XENONnT will contain about 6 t LXe in the target All infrastructure built already to accommodate XENONnT Currently > 8 t of LXe purchased New PMTs delivered and being measured New concept TPC design finalized: Raw materials under procurement and screening ongoing Sensitivity goal: cm 2 for 50 GeV/c 2 WIMP mass for 20 t y exposure Teresa Marrodán Undagoitia (MPIK) Liquid noble gases Heidelberg, April / 29

21 DARWIN: the ultimate WIMP detector R&D and design study for a liquid xenon observatory Design phase on-going, followed by construction and commissioning TPC of 2.6 m diameter & 2.6 m drift length 7 years necessary to exploit the complete sensitivity 50 t LXe total (40 t in the TPC) Location: letter of intent sent to LNGS DARWIN, JCAP 1611 (2016) 017 Teresa Marrodán Undagoitia (MPIK) Liquid noble gases Heidelberg, April / 29

22 DARWIN physics Goal: measure WIMP properties / ultimate cross-section sensitivity DARWIN, JCAP 1611 (2016) no.11, 017, arxiv: Neutrino physics channels become available: Electronic recoils from solar neutrinos 7 ev/day in 30 t and E = (2-30) kev ee 3.5 t of 136 Xe in DARWIN without isotopic enrichment Nuclear recoils from coherent neutrino scattering: solar, supernova and atmospheric ν s 90 events/t/y from 8B-ν s above 1 kev ee Teresa Marrodán Undagoitia (MPIK) Liquid noble gases Heidelberg, April / 29

23 ] Summary Sensitivity for dark matter searches has progressed rapidly XENON1T, PandaX-II and DEAP detectors taking data! XENONnT, LZ and DarkSide20k are the upcoming devices to (hopefully) investigate the dark matter properties The future DARWIN and GADMC are designed with sensitivities down to the neutrino floor 2 Cross section [cm Germanium detector Cryogenic bolometer Liquid xenon detector Liquid argon detector Bubble chamber Neutrino background 2 50 GeV/c Year Figure updated from J. Phys. G43 (2016) 1, & arxiv: Teresa Marrodán Undagoitia (MPIK) Liquid noble gases Heidelberg, April / 29

24 PandaX-II and the future PandaX-xT Latest dark matter results from 54-ton-day exposure in 2017 PRL 119, (2017) Currently acquiring blinded science data Future upgrade to PandaX-xT with 4 ton target, assembly and commissioning Figure from Jianglai Liu UCLA 2018 Teresa Marrodán Undagoitia (MPIK) Liquid noble gases Heidelberg, April / 29

25 ArDM experiment Mass: 850 kg liquid argon (in target) Technology demonstrator Installed at Canfranc (Spain) A year long operation of 2 tons of LAr in single phase Run 2: operation in dual-phase started Jan 2018 Purification and data analysis on-going Teresa Marrodán Undagoitia (MPIK) Liquid noble gases Heidelberg, April / 29

26 Charge energy scale for LAr and LXe Figure from arxiv: Teresa Marrodán Undagoitia (MPIK) Liquid noble gases Heidelberg, April / 29

27 Light sensors Requirements for a dark matter experiment: I I I Low radioactivity & low dark rate (background rate only few Hz!) UV sensitivity & stable performance at cold temperatures Low power consumption & high QE/CE APD, SiPMT, hybrid tubes... State-of-the-art 3 photomultipliers from Hamamatsu: I I R11065 (for LAr) used by DarkSide R11410 (for LXe) for XENON1T, PandaX and LZ Low-radioactive photosensors 238 U & 228 Th < 1 mbq/pmt For reference: 1 Banana 15 Bq in 40 K High quantum efficiency: 36 % in average for XENON1T Stable performance at 100 C XENON1T testing setup for R at MPIK Teresa Marrodán Undagoitia (MPIK) Liquid noble gases Heidelberg, April / 29

28 Cross sections for WIMP elastic scattering Spin-independent interactions: coupling to nuclear mass σ SI = m 2 N 4π(m χ+m N ) 2 [Z f p + (A Z ) f n ] 2 f p,n : effective couplings to p and n. Spin-dependent interactions: coupling to nuclear spin σ SD = 32 π G mχ F 2 m2 N (m χ+m JN+1 N ) 2 J N [a p S p + a n S n ] 2 S p,n : expectation of the spin content of the p, n in the target nuclei a p,n : effective couplings to p and n. Teresa Marrodán Undagoitia (MPIK) Liquid noble gases Heidelberg, April / 29

29 DARWIN: spin dependent sensitivity DARWIN, JCAP 1611 (2016) no.11, 017, arxiv: Teresa Marrodán Undagoitia (MPIK) Liquid noble gases Heidelberg, April / 29