Particle Dark Matter An Introduction into Evidence, Models, and Direct Searches
Lecture for ESIPAP 2016 European School of Instrumentation in Particle & Astroparticle Physics Archamps Technopole XENON1T January 25th, 2016
Uwe Oberlack Institute of Physics & PRISMA Cluster of Excellence Johannes Gutenberg University Mainz http://xenon.physik.uni-mainz.de Outline
● Evidence for Dark Matter: ▸ The Problem of Missing Mass ▸ In galaxies ▸ In galaxy clusters ▸ In the universe as a whole
● DM Candidates: ▸ The DM particle zoo ▸ WIMPs
● DM Direct Searches: ▸ Detection principle, physics inputs ▸ Example experiments & results ▸ Outlook
Uwe Oberlack ESIPAP 2016 2 Types of Evidences for Dark Matter
● Kinematic studies use luminous astrophysical objects to probe the gravitational potential of a massive environment, e.g.: ▸ Stars or gas clouds probing the gravitational potential of galaxies ▸ Galaxies or intergalactic gas probing the gravitational potential of galaxy clusters
● Gravitational lensing is an independent way to measure the total mass (profle) of a foreground object using the light of background sources (galaxies, active galactic nuclei).
● Comparison of mass profles with observed luminosity profles lead to a problem of missing mass, usually interpreted as evidence for Dark Matter.
● Measuring the geometry (curvature) of the universe, indicates a ”fat” universe with close to critical density. Comparison with luminous mass: → a major accounting problem! Including observations of the expansion history lead to the Standard Model of Cosmology: accounting defcit solved by ~68% Dark Energy, ~27% Dark Matter and <5% “regular” (baryonic) matter.
● Other lines of evidence probe properties of matter under the infuence of gravity: ▸ the equation of state of oscillating matter as observed through fuctuations of the Cosmic Microwave Background (acoustic peaks). ▸ formation of structure in the universe, probing the velocity dispersion of (dark) matter.
Uwe Oberlack ESIPAP 2016 3 The Problem of Missing Mass
Uwe Oberlack ESIPAP 2016 4 Evidence for Dark Matter In Galaxies Scale: 1021 m (~10 5 lightyears)
Spiral galaxies Dwarf Spheroidal galaxies
M31, NASA
Fornax David Malin, Anglo-Australian Observatory.
Uwe Oberlack ESIPAP 2016 5 Our Galaxy The Milky Way
Our view from inside the disk (in near infrared radiation)
2MASS Allsky survey
Edge-on view (sketch)
Uwe Oberlack ESIPAP 2016 6 Stellar Orbits
Pearson Education
Uwe Oberlack ESIPAP 2016 7 Evidence for Dark Matter in Spiral Galaxies Rotation curves (orbital velocity vs. galactocentric radius) remain fat well beyond the edge of the visible disk in spiral galaxies.
Disk + DM Halo
Disk only
Rotation curves of nearby galaxies Rotation curve of the Milky Way (Sofue & Rubin ARAA 2001) (A. Klypin et. al, ApJ. 573, 2002) Uwe Oberlack ESIPAP 2016 8 Via Lactea 2 (2008) http://www.ucolick.org/~diemand/vl Dark Matter Halo
Observer
Uwe Oberlack ESIPAP 2016 9 MOND: Modifed Newtonian Dynamics Mordehai Milgrom 1983 Change Newton´s force law for low values of acceleration a:
For large r, a << a0:
For a circular orbit: so is independent of r.
If, a >> a0: 1, so v remains
● MOND does well for rotation curves but does not explain the movement of galaxies in clusters or cosmological observations. ● MOND is a non-relativistic theory, phenomenological, and ad hoc. More sophisticated relativistic theory (e.g., TeVeS) also has difculty explaining cosmological data.
Uwe Oberlack ESIPAP 2016 10 Local DM density from vertical motions
Uwe Oberlack ESIPAP 2016 11 Evidence for Dark Matter in Galaxy Clusters
• Orbital velocities of galaxies exceed escape velocity estimated from visible mass in galaxies (Zwicky 1933). • X-ray gas: pressure too great for visible mass. Traces gravitational potential. NOAO/Kitt Peak: Uson, Dale • Gravitational lensing: measures total NASA/CXC/IoA: Allen et al. mass distribution in galaxy clusters. Scale: ~1022 m (~106 lightyears)
W. Couch, R. Ellis, NASA G. Kochanski, I. Dell'Antonio, T. Tyson, 2002 Uwe Oberlack ESIPAP 2016 12 Velocity dispersion in galaxy clusters Fritz Zwicky (1933) used the velocity dispersion of galaxies in the Coma cluster and the virial theorem 1 E = − E kin 2 pot
to estimate the mass of the cluster MCluster. Comparing this mass to the luminosity of the galaxies in the cluster, using empirical relations between luminosity and mass for stars, he found:
Mlum ~ 1/400 MCluster
Something is missing : Dark Matter ?
Helvetica Physica Acta 6 (1933), 110
Uwe Oberlack ESIPAP 2016 13 X-Ray Observations of Galaxy Clusters Baryonic matter in galaxy clusters is dominated by X-ray emitting hot gas. The temperature of the hot gas tells us the total cluster mass. 85% dark matter 13% hot gas Zwicky knew 2% stars only about this! This results from the assumption that the observed clusters are
virialized, i.e., Epot = 2 Ekin Kinetic energy=thermal energy 1 2 3 m ⟨ v ⟩= k T 2 ¯ 2 virial
with avg. particle mass m¯ ≈1.23mH Boltzmann constant: k=1.38065×10−23 J / K ⇒ Velocity dispersion: σ=√ ⟨ v2 ⟩ 3 k T 3 1 T σ= ≈1.4×10 km s− √ m¯ √ 108 K 3 −1 7 Uwe Oberlack ESIPAP 2016 σ∼10 km s ,T ∼(2−11)×1014 K Gravitational Lensing
General Relativity: A massive object (e.g., a galaxy cluster) curves spacetime. Light follows geodesics. Hence a massive object acts as a gravitational lens for light from a distant source. Gravitational lensing measures the total mass enclosed by the light rays, independent of the type of matter. NASA/ESA Uwe Oberlack ESIPAP 2016 15 Gravitational Lensing: Strong Lensing
NASA/ESA
Gravitational lensing measures the total mass enclosed by the light rays, independent of the type of matter.
Uwe Oberlack ESIPAP 2016 16 Weak Lensing
● Line of sight near galaxy cluster: strong lensing (long arcs)
● Further out: weaker distortions, but more abundant. → weak lensing
● Measure total mass distribution in galaxy clusters
NASA HST
Bullet cluster blue: total mass distribution from weak lensing NASA Uwe Oberlack ESIPAP 2016 17 MergingMerging GalaxyGalaxy Clusters:Clusters: MissingMissing massmass oror modificationmodification ofof gravity?gravity?
D. Clowe et al., 2006 Bullet Cluster
18 Uwe Oberlack ESIPAP 2016 The Bullet Cluster
● “Bullet cluster” (z~0.3) is an ongoing merger of two galaxy clusters.
● Cores passed through each other ~100 million years ago (recent!).
● Weak lensing observations (blue) trace the total mass distribution.
● Known property of clusters: bulk of regular (baryonic) matter consists of hot intra- cluster gas. Stars contribute just a little.
● Chandra X-ray observations (pink) trace hot intracluster gas, i.e., most baryons. D. Clowe et al., Astrophys. J. 648 (2006) L109 ● Stars and Dark Matter are collisionless, whereas gas (plasma) experiences ram pressure. ● Mass cluster >> Mass gas ● Bulk of total mass ofset with respect to ● Gas is ofset with respect to total matter bulk of baryonic matter. distribution. ⇒Dark Matter! But: these systems are rare, dynamics ... and not modifed gravity. complicated, possible counter example, etc.
Uwe Oberlack ESIPAP 2016 19 Scale: ~1026 m Planck Collab. arxiv:1303.5062 Evidence for Dark Matter (1010 lightyears) CMB Ω ≈ 5 Ω from Cosmology m b
● Cosmic Microwave Background. ▸ Uniformity at age 380,000 yr. ▸ Flatness of the universe ▸ Baryon density, etc.
● Supernovae as standard candles. ▸ Expansion history of the universe.
● Galaxy surveys (wide or deep) and Simulations of structure formation. ▸ Large scale structure. ▸ Early structure formation. First stars. Quasars and galaxies.
● Big Bang Nucleosynthesis and light element Dark Energy abundances observed in the early universe. Dark Matter ▸ Limit on baryon density, consistent Baryons with CMB. 68.3% ● Baryon Acoustic Oscillations 26.8% ▸ standard ruler ● ... 4.9%
Uwe Oberlack ESIPAP 2016 20 Multipole Expansion of CMB WMAP after dipole subtraction Expansion in spherical l=2 harmonics:
Pair correlation function: l=3
2 C (Δ T ) = l (l + 1) l Uwe Oberlack 2 π ESIPAP 2016 NASA/WMAP 21 CMB Power Spectrum & Baryon Density
P. Schneider
Relative strength of acoustic peaks provides Ωm and Ωb independently.
Uwe Oberlack ESIPAP 2016 22 CMB as seen by Planck: Power Spectra
Planck collaboration, arxiv:1303.5062 Uwe Oberlack ESIPAP 2016 23 → Dark Matter is non-baryonic.
Uwe Oberlack ESIPAP 2016 24 Structures in galaxy maps look very similar to the ones found in models in which dark matter is “cold” (v ≪ c) and not interacting, supporting WIMPs as Dark Matter candidates.
Uwe Oberlack ESIPAP 2016 25 Cold Dark Matter – Structure Formation
V. Springel, C. S. Frenk, S. D. M. White Nature 440, 1137 (2006) Uwe Oberlack ESIPAP 2016 26 → Dark Matter is non-relativistic: cold, or at least not hot.
Uwe Oberlack ESIPAP 2016 27 Non-baryonic Dark Matter or Alternative Theories of Gravity?
CMB Ωm≈ 5 Ωb Planck
3rd peak only with Dark Matter
● Relative strength of acoustic peaks provides
Ωm and Ωb independently.
● One can also test for alternative theories of gravitation (e.g., TeVeS): no alternative theory can do without Dark Matter.
Uwe Oberlack ESIPAP 2016 28 Non-baryonic Dark Matter or Alternative Theories of Gravity? Matter power spectra SDSS
TeVeS
M D ΛC
Dodelson, arXiv:1112.1320
Uwe Oberlack ESIPAP 2016 29 Outline
● Evidence for Dark Matter: ▸ The Problem of Missing Mass ▸ In galaxies ▸ In galaxy clusters ▸ In the universe as a whole
● DM Candidates: ▸ The DM particle zoo ▸ WIMPs
● DM Direct Searches: ▸ Detection principle, physics inputs ▸ Example experiments & results ▸ Outlook
Uwe Oberlack ESIPAP 2016 30 What do we know about Dark Matter?
● Gravitationally interacting The Standard Model ► How we know about Dark Matter
● Stable or long-lived
► ΩDM = 0.27
● Electrically neutral ► Dark Matter
● Non-baryonic ► does not couple with plasma ► CMB, Big Bang nucleosynthesis
● Cold or warm - not hot (relativistic) ► Structure formation, CMB
● Constraints from ► accelerator searches ► direct searches ► indirect searches
Dark Matter requires physics beyond the Standard Model.
Uwe Oberlack ESIPAP 2016 31 Particle Dark Matter Candidates
● Type I: Candidates that exist sorry!
● Type II: Candidates in well-motivated frameworks (*) ► solve genuine particle physics problems, a priori unrelated to dark matter ► have interactions and masses specifed within a well-defned particle physics model
● Type III: All other candidates
(*) defnition adopted from P. Gondolo
Uwe Oberlack ESIPAP 2016 32 Particle Dark Matter Candidates
● Type I: Candidates that exist
► standard neutrinos (only a small fraction of ΩDM)
● Type II: Candidates in well-motivated frameworks ► lightest supersymmetric particle (neutralino, sneutrino, gravitino, axino): CDM ► axion: (usually) CDM ► heavy neutrinos: WDM
● Type III: All other candidates ► scalar singlet DM, maverick WIMP, WIMPZILLA, B-balls, Q-balls, self-interacting dark matter, string-inspired dark matter, etc.
Uwe Oberlack ESIPAP 2016 33 Weakly Interacting Massive Particles (WIMPs): A thermal relic at just the right density WIMP pair creation and annihilation with SM particles: χ+χ ↔f +f¯ , etc. Boltzmann equation: 1 dn χ =−3 H n −〈σ v〉(n2 −n2 ) dt χ eff χ χ ,eq 2 Decrease due to increasing <σ v> universe expansion a
2 1 kT≫mχc : equilibrium of WIMP annihilation and pair creation 3 2 2 kT expansion rate: H > Γann ~ nχ <σa v> −27 3 −1 J. Feng, ARAA 2010 2 10 cm s results in relic density: Ωχ h ≈ see also Kolb & Turner 1990 ⟨σ a v ⟩ If σ (~ 1/m 2) related to the electroweak scale → Ω h2 ~ O(0.1) → “WIMP miracle” a X χ ✓ Massive particles: average WIMP velocity is non-relativistic at times of structure formation. Uwe Oberlack ESIPAP 2016 → Cold Dark Matter 34 On the WIMP “Miracle” Defning freeze out to be the time when n⟨σAv⟩ = H: J. Feng, ARAA 2010.48:495-545 Dark Matter as thermal WIMP: mX ~ 100 GeV – 1 TeV Uwe Oberlack ESIPAP 2016 35 WIMPs have been most extensively studied in the SUSY – MSSM SUSY framework, but numerous other theories can provide WIMPs too. MSSM: Minimal Supersymmetric Standard Model ● 105 (!) additional physical parameters: (e.g., PDG http://pdg.lbl.gov/, Supersymmetry Part I) ► Masses (scalar masses, gauginos) ► Requires (at least) 2 Higgs bosons in the SM + 2 Higgsinos ► CP phases ► Mixing angles (e.g., for neutralinos & charginos), … Uwe Oberlack ESIPAP 2016 36 WIMP Scattering Cross Sections Example SUSY (direct searches are sensitive to other models as well) ● Cross sections χ – quark and χ – gluon with various SUSY models cover large parameter space: constrained by accelerator and direct search experiments, and cosmology. ● Spin-independent interactions: χ - quark (SI, scalar) coupling to mass of nucleus. Coherence → σ∝ A2 Jungmann et al. '96 Phys.Rep. ● Spin-dependent interactions: χ - quark (SD, axial) coupling of spins of nucleus and neutralino.Interactions with paired nucleons in the same energy state cancel. → no A2 enhancement σ ∝ (J+1)/J Uwe Oberlack ESIPAP 2016 37 CMB Ω ≈ 5 Ω Dark Matter Detection Methods m b ● Astrophysics / Cosmology: Gravitational Efects. ▶ Rotation curves of spiral galaxies ▶ Orbital velocities of galaxies in clusters (Zwicky 1933) ▶ Colliding clusters (Bullet cluster) ▶ CMB, large scale structure, lensing ● Direct Detection: ▶ WIMP scattering ▶ Axion searches, ... ● Indirect Detection: from annihilation or decay Aqarius Project ▶ Cosmic rays AMS-02 / PAMELA positrons Fermi, ATIC, HESS electrons; Anti-deuterons? ▶ Neutrinos ▶ Gamma-rays ● Accelerator-based Creation and Measurement: ▶ Missing energy / momentum (+ jets + lepton(s)) ▶ Search for (possibly) DM-related particles (SUSY, extra dimensions, dark photon) Uwe Oberlack ESIPAP 2016 38 Complementarity in Dark Matter Searches: Direct Searches, Indirect Searches, and the LHC SM SM Model c Model b Model a ... L e.g. pMSSM t H c e.g. CMSSM C e r i d n i m0, m1/2, A0, tan β, sign(μ) direct χ χ LHC Indirect Searches Direct Searches σ ( ) squark mass SD ν σSI , mχ gluino mass σa , mχ (γ) ... Uwe Oberlack ESIPAP 2016 39 Outline ● Evidence for Dark Matter: ▸ The Problem of Missing Mass ▸ In galaxies ▸ In galaxy clusters ▸ In the universe as a whole ● DM Candidates: ▸ The DM particle zoo ▸ WIMPs ● DM Direct Searches: ▸ Detection principle, physics inputs ▸ Example experiments & results ▸ Outlook Uwe Oberlack ESIPAP 2016 40 Via Lactea 2 (2008) http://www.ucolick.org/~diemand/vl GalacticGalactic DarkDark MatterMatter Observer Uwe Oberlack ESIPAP 2016 41 WIMP Dark Matter Direct Detection ● Scattering of WIMPs χ of nuclei A. → nuclear recoil ► elastic or inelastic? ► spin-independent (~A2) or spin-dependent? ● Energy spectrum: v Vogelsberger et al. 2008 dR ρχ σs 2 esc f (v , t ) 3 F E d v = 2 ∣ ( )∣ ∫v dE 2 m μ min v χ F(E) f(v) 2 −(v + v (t )) f (v , t ) ∝ exp E 2 2 ( σv ) 4 2 ▶ m ~ 10 - 10 GeV/c , μ = (m m )/(m + m ) χ χ n χ n ▶ v ~ 230 km/s χ ▶ “Standard” spherical halo: Featureless recoil spectrum ▶ ρχ/mχ: local number density of WIMPs 2 3 ρχ ~ 0.3 GeV/c /cm , ρχ/mχ μ 10 / L ▶ σs cross section per nucleus. Typical rate < 10-3 events / kg / day Uwe Oberlack ESIPAP 2016 42 Cross Section for WIMP-Nucleon Scattering Scalar (spin-independent) scattering At fnite momentum transfer: Form factor: Fourier transform of nuclear density 2 2 q⋅r F q = ∫ r exp i dr ∣ { ℏ } ∣ 2 3 j 1 qR1 2 F E r = exp [−qs ] q R1 At zero momentum transfer: 2 Momentum transfer: q = s mN E r 4 2 coherent = [Z f p A − Z f n ] j : first spherical Bessel function scattering 1 2 2 m m R 1 = R0 − 5 s Woods-Saxon N m ≪ mN : ≈ m reduced mass = 1/ 3 parametrization: m mN m ≫ m : ≈ m R0 ≈ 1.2 fm A N N 1 s ≈ 1 fm f p , f n : scattering amplitudes protons, neutrons = 0 r − R 1 exp 0 Form factor s Uwe Oberlack ESIPAP 2016 43 Backgrounds in Direct DM Search Cross-sections are very small: <10-44 cm2 or 10-8 pb (spin-independent). Without background, sensitivity ∝ (mass × exposure time)-1 With background subtraction ∝ (M t)-1/2 until limited by systematics. Backgrounds: Gamma-rays & beta decays: 106 ▸ ~100 events/kg/day ▸ Need very good β and γ background ] 1 - discrimination. r y ▸ Shielding: low-activity lead, water, noble 2 m [ liquids (active), liquid N , ... 2 y t i s Neutrons from (α, n) and spontaneous n e t n fssion (concrete, rock, etc.): I ▸ n ~ 1 event/kg/day (LNGS) o u ▸ Neutron moderator (polyethylene, M parafn, ...) Neutrons from CR muons: ▸ Rate depending on depth. 101 ▸ μ-veto, n-veto, shielding 103 104 α decays from natural decay chains Depth [meters water equivalent] ▸ surface effects, recoiling nucleus Uwe Oberlack ESIPAP 2016 44 DM Detector Overview Detection Principles Bubble Formation Tracking COUPP, PICASSO, Drift, DM-TPC, PICO MIMAC, NIT Ionization CoGeNT Super-CDMS, LAr: DarkSide-50, ArDM Edelweiss-III LXe: XENON, LUX Phonons CRESST-II Scintillation DAMA/LIBRA KIMS, XMASS, DEAP/CLEAN Uwe Oberlack ESIPAP 2016 45 Uwe Oberlack ESIPAP 2016 Kaixuan46 Ni Cryogenic Germanium Detectors ● SuperCDMS @ Soudan, USA. SNOLab, CA in the future ● EDELWEISS-III @ LSM, France Uwe Oberlack ESIPAP 2016 47 Cryogenic Detectors John L. Orrell Uwe Oberlack ESIPAP 2016 48 CDMS-II / SuperCDMS: Phonons + Charge ● Located at Soudan mine (Minnesota) ● Ge crystals operated at ~40 mK ● Fast phonon read-out with Tungsten Transition-edge sensors (TES) → direct measurement of nuclear recoil energy → SQUID Readout ● Low-voltage drift for charge read-out → e.m. background suppression with charge / phonon ratio ● Suppression of surface events with phonon timing signal (CDMS-II), now: surface field Uwe Oberlack ESIPAP 2016 49 PLB 681 (2009) 305-309 Edelweiss – Interleaved Electrodes [arXiv:0905.0753] ● Modifcation of E feld near the surfaces with interleaved electrodes ● Use ‘b’ and ‘d’ signals as vetos against surface events ● Separation of surface and volume events. ● Beta rejection ~ 10-5 ● Substantial improvement over discrimination based on phonon timing (CDMS) Uwe Oberlack ESIPAP 2016 50 SuperCDMS: Focussing on Low-Mass WIMPs (1-10 GeV/c2) arXiv:1402.7137 Uwe Oberlack ESIPAP 2016 51 Detectors with Scintillation Only ● NaI(Tl) crystals: DAMA/LIBRA, Anais, DM-Ice, Sabre ● CsI(Tl) crystals: KIMs ● LAr single phase: DEAP-3600, MiniClean ● LXe single phase: XMASS Uwe Oberlack ESIPAP 2016 52 Background Rejection in Single Phase Liquid Noble Gas Scintillator Detectors ● Fiducialization O(few cm) ● Single vs. multiple scatter events - poor! ● Pulse shape discrimination (LAr): ► nuclear recoils (NR): predominantly fast component ► electron recoils (ER): predominantly slow component ● Active veto systems E. Pantic Uwe Oberlack ESIPAP 2016 53 LAr Singe Phase Experiments DEAP-3600 / 1000kg MiniClean 500 / 150kg 1406.0462 1403.4842 Uwe Oberlack ESIPAP 2016 54 LAr Singe Phase Experiments Pulse shape discrimination crucially depends on # of photons. PSD power = O(107-8) achieved in DEAP-1, SCENE, DarkSide-50 f90 = fraction of S1 within first 90 ns ER: f90 ~ 0.3 NR: f90 ~ 0.7 Uwe Oberlack ESIPAP 2016 55 Dual Phase Liquid Noble Gas TPCs XENON100 LUX Panda-X 161 kg 370 kg 125 kg LXe ≥34 kg ≥118 kg ≥25 kg ArDM DarkSide-50 LAr 850 kg 46 kg ~several ≥37 kg 100 kg Uwe Oberlack ESIPAP 2016 56 The Dual Phase Liquid Noble Gas TPC (Ar, Xe) ● WIMP recoil on nucleus in dense Example: liquid XENON100 → Ionization + UV Scintillation ● Detection of primary scintillation light (S1) with PMTs. Ar: wavelength shifting necessary ● Charge drifts towards liquid/gas interface (low field: ~0.1-1 kV/cm). ● Charge extraction liquid/gas at high field between ground mesh (liquid) and anode (gas) ● Charge produces proportional scintillation signal (S2) in the gas phase (high field: ~10 kV/cm) ● 3D position measurement ► X/Y from S2 signal. Resolution few mm. ► Z from electron drift time (~0.3 mm). Uwe Oberlack ESIPAP 2016 57 Background Rejection in Dual Phase Liquid Noble Gas TPCs ● Fiducialization O(mm) ● Single vs. multiple scatter events ● Pulse shape discrimination (LAr): ► nuclear recoils (NR): predominantly fast component ► electron recoils (ER): predominantly slow component ● S2/S1 (LXe) ► NR: small S2/S1 ► ER: large S2/S1 ● Active veto systems E. Pantic Uwe Oberlack ESIPAP 2016 58 DarkSide-50 Hall C @ LNGS ● Click to add text LArTPC ● 35.6 × 35.6 cm2 ● TPB coated ● 38 Hamamatsu R11065 3” PMTs ● (7.9 ± 0.4) PE/keV @ zero field Water Cherenkov Liquid Scintillator Veto Muon Veto ● 4 m diam. SS sphere ● ● 11 m diam. × 10 m 30 t borated liq.sci. ● 10 7 ● ~1 kt ultrapure water B(n,α) Li ● ● lam. Tyvek-PE-Tyvek Lumirror reflective foil ● ● 80 ETL 9351 8” PMTs 110 Hamamatsu R5912 ● former Borexino CTF 8” PMTs Uwe Oberlack ESIPAP 2016 59 thanks to C. Galbiati for valuable input Background Discrimination in a LAr-TPC: DarkSide-50 arxiv:1410.0653 8.6 - 65.6 keVee 80 PE ~ 38 keVnr DM window threshold 180 PE Nuclear recoil acceptance Expected <0.1 39Ar evts in DM window Uwe Oberlack ESIPAP 2016 out of 15×106 evts in total 60 DarkSide-50: WIMP Dark Matter Limit (SI) ● (1422 ± 67) kg d background-free with atmospheric argon → underground argon (39Ar depleted) ● 6×10-44 cm2 @ 100 GeV/c2 ● 4 neutron events observed – vetoed by Liq. Sci. veto arxiv:1410.0653 Uwe Oberlack ESIPAP 2016 61 Background Discrimination in Dual Phase Liquid Xenon TPC's Ionization/Scintillation Ratio 3D Position Resolution: S2/S1 fducial cut, singles/multiples XENON100 gamma-rays (60Co) neutrons (AmBe) Uwe Oberlack ESIPAP 2016 62 Uwe Oberlack ESIPAP 2016 63 Uwe Oberlack ESIPAP 2016 64 Uwe Oberlack ESIPAP 2016 65 Uwe Oberlack ESIPAP 2016 66 Status of Spin-independent WIMP Interactions as of Dec. 2015 Uwe Oberlack ESIPAP 2016 67 The XENON Program -48 2 GOAL: Explore WIMP Dark Matter to a sensitivity of σSI ~10 cm . CONCEPT: ● Target LXe: excellent for DM WIMPs scattering. Sensitive to both axial and scalar coupling. ● Detector: two-phase LXeTPC: 3D position sensitive calorimeter. ● Background discrimination: – simultaneous charge & light detection – single site interactions, fducialization, self shielding Location: LNGS ● High light yield + proportional scintillation → low energy threshold for nuclear recoils (~ 5 keV). PHASES: R&D XENON10 XENON100 XENON1T XENONnT Start: 2002 2005-2007 2007 → ... 2011 → DM search '15 2018 → Proof of concept. Ongoing DM search. Construction ongoing. Total mass: 14 kg Total mass: 161 kg Total mass: ~ 3.3 t 15 cm drift. 30 cm drift. 1 m drift. Best limit in '07: Best limits in '11, '12: Goal: Goal: σ ~10-43 cm2 -45 2 -47 2 -48 2 SI σSI~ 2 x 10 cm σSI ~ 2 x 10 cm σSI ~ 10 cm Uwe Oberlack ESIPAP 2016 68 The XENON100 TPC Astropart. Phys. 35 (2012), 573 TPC Top array: 98 PMTs R8520, QE >32% @ 178 nm (~25% on top array) ● 161 kg Xe, 62 kg target Bottom array: 80 PMTs ● 30 cm drift ● radiopurity: ► material screening ► 85Kr: distillation column ► 222Rn: avoid/monitor ● LXe veto ● Passive shielding: water, Pb, PE, copper Uwe Oberlack ESIPAP 2016 Veto PMTs 69 Beyond WIMPs: Constraining Solar Axions Phys. Rev. D 90, 062009 (2014), arxiv:1404.1455 ● Sun postulated to be a source of axions due to axio-electric effect. ● But: mass range probed here for solar axions not the range of conventional DM candidate axions (~μeV) ● Blue: expected signal for solar 2 axions with mA < 1 keV/c for previously existing upper limit (EDELWEISS-2). ● New upper limit on axio-electric coupling: −12 gAE < 7.7 × 10 (90% CL). Uwe Oberlack ESIPAP 2016 70 Beyond WIMPs: Constraining Galactic DM ALPs Phys. Rev. D 90, 062009 (2014), arxiv:1404.1455 ● ALPs in the keV range are potential DM candidates. ● Analysis assumes all local DM to be ALPs. ● Expected event distribution in XENON100 for galactic ALPs with −12 coupling gAe= 4 × 10 ● Monoenergetic signal is given by the energy resolution of the detector at the relevant S1. −12 ● gAe < ~ 1 × 10 (90%) Uwe Oberlack ESIPAP 2016 71 DAMA/LIBRA PMT & base R. Bernabei et al. arXiv:0804.2738, Eur.Phys.J. C73 (2013) 12, 2648 ● Successor of DAMA/NaI experiment, located at LNGS, Italy ● 5x5 array of 9.7 kg NaI(Tl) crystals viewed by 2 PMTs each. ● PMTs with single photoelectron threshold, operating in coincidence. ● Total mass: DAMA/NaI 1996-2002: ~100 kg DAMA/LIBRA 2003-2008: 232.8 kg DAMA/LIBRA: since 11/2008: 242.5 kg ● Heavy shield: ► >10 cm Cu ► 15 cm Pb + Cd foils ► 10/40 cm PE/parafn ► ~1 m concrete ● Radon sealing Uwe Oberlack ESIPAP 2016 72 DAMA/LIBRA Annual Modulation R. Bernabei et al. EPJ C 56, 333 (2008), arxiv:0804.2741 Eur.Phys.J. C73 (2013) 12, 2648 solid line: p=1yr, phase=152.5 d ● 1.33 ton × yr, 14 annual cycles ● Modulation in 2-6 keV single hits: 9.3 σ 0.0112 ± 0.0012 cts/d/kg/keV ● Total single rate ~1 cts/d/kg/keV 3 ● 0 December Standard DM distribution: < ~5% modulation km /s ● Period & phase (144 ± 7) d: about right for DM. ● No annual modulation in 6-14 keV. ~ ● No annual modulation in multiple hits. 23 2 60° km ● DM detection? /s 30 ● Conflict with other experiments in standard scenarios k June m /s that test the larger steady state effect. Uwe Oberlack Drukier, Freese, Spergel PRD 86 ESIPAP 2016 73 Freese et al. PRD 88 XENON100: new Constraint on DAMA Modulation as DM Interpretation Even if DM only interacts with electrons at tree-level, loop induced DM-hadron interactions dominate → back to the usual NR limits J. Kopp et al. PRD 80, 083502 (2009) Loop-hole: axial-vector couplings A⊗ A: loop-efects vanish, WIMP-electron couplings are not suppressed. efective DM-electron interaction efective DM-nucleus interaction at 1-loop level Uwe Oberlack ESIPAP 2016 74 XENON100: new Constraint on DAMA Modulation as DM Interpretation Loop-hole: axial-vector couplings A⊗ A: loop-efects vanish, WIMP-electron couplings are not suppressed. XENON100 excludes DAMA as being due to ● WIMP-electron axial-vector couplings at 4.4σ (interpreting all XENON100 events as signal) ● luminous dark matter at 4.6σ ● mirror dark matter at 3.6σ Uwe Oberlack ESIPAP 2016 75 XENON1T ● ~ 1 m3, ~ 3 t LXe, ~ 1 t fiducial mass ● Water Cherenkov Muon Veto ~10 m x 9.6 m ● ER background < 5 x 10-5 ev / kg / keV / day ● Kr/Xe < 0.5 ppt & Rn/Xe < 1 μBq/kg ● Project approved and funded XENON100 (~50% NSF, ~50% Europe + Israel) ● Design of major systems completed ● Construction ongoing. LNGS, Italy XENON1T in Hall B Uwe Oberlack ESIPAP 2016 76 XENON1T Uwe Oberlack ESIPAP 2016 77 Uwe Oberlack ESIPAP 2016 78 XENON1T Background Estimate ● Complete Monte Carlo simulation of the detector: TPC, PMTs, cryostat, water, shield in GEANT4. n-background Informed by material screening. ● Neutrons from (α,n) and spontaneous fission predicted with SOURCES- 4A. ● Estimate in 4-50 keVnr: ▸ radiogenic neutrons: 0.6 / ton / year total. arxiv:1512.07501 Uwe Oberlack ESIPAP 2016 79 XENON1T Sensitivity to Coherent Neutrino-Nucleon Scattering Uwe Oberlack ESIPAP 2016 80 XENONnT ● XENONnT: larger TPC & larger inner vessel to fit inside XENON1T outer cryostat. Other systems will be largely reused. ● Aim: 20 ton-years exposure, reduced background to reach few 10-48 cm2 sensitivity. ● Start: ~2018 100 XENON 1T XENON nT XENON Uwe Oberlack ESIPAP 2016 81 Current Status and Future Goals Spin-independent sensitivity 0 ON10 XEN Measurement ON1T of coherent XEN ν scattering NnT ENO LZ , X in Darw Uwe Oberlack ESIPAP 2016 82