An experimental overview of direct dark matter searches
Download
1 / 31

AN EXPERIMENTAL OVERVIEW OF Direct Dark Matter Searches - PowerPoint PPT Presentation


  • 67 Views
  • Uploaded on

AN EXPERIMENTAL OVERVIEW OF Direct Dark Matter Searches. Henrique Araújo Imperial College London IOP2010 – JOINT HEPP/APP GROUP MEETING 29-31 March 2010, University College London. What are we looking for?. Scalar (SI) and axial-vector (SD) c -N interactions (neutral current exchange):.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' AN EXPERIMENTAL OVERVIEW OF Direct Dark Matter Searches' - kylee


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
An experimental overview of direct dark matter searches

AN EXPERIMENTAL OVERVIEW OFDirect Dark Matter Searches

Henrique Araújo

Imperial College London

IOP2010 – JOINT HEPP/APP GROUP MEETING

29-31 March 2010, University College London


What are we looking for
What are we looking for?

  • Scalar (SI) and axial-vector (SD) c-N interactions

  • (neutral current exchange):

WIMPs attract most experimental effort,

but axion searches are a growth industry

I assume here that the Lightest SUSY Particle

is the neutralino, c, which is a great WIMP

WIMPs should scatter off ordinary nuclei

producing measurable nuclear recoils

But, essentially, WIMP searches are not really (PP-)model dependent…

H. Araújo


Low energy nuclear recoils
Low energy nuclear recoils

  • Elastic scatter off nucleus:

    • Decreasing, featureless spectrum of low-energy recoils (<~50 keV)

    • Rate depends on target mass & spin, WIMP mass & spin, DM halo, …

    • Neutrons are irreducible background

  • Inelastic scatter off nucleus:

    • Short-lived, low-lying excited states (easier signature?)

    • 129Xe(3/2+→1/2+) + g(40 keV), 73Ge(5/2+→9/2+) + g(13 keV)

    • Neutrons are irreducible background

  • Inelastic dark matter (iDM):

    • “particles will scatter at DAMA but not at CDMS” (Smith & Weiner 2001)

    • Recoil spectrum with threshold (mass splitting, d)

    • Neutrons are irreducible background

H. Araújo


Elastic scattering rates
Elastic scattering rates

Canonical model: not great, but we’re all in this together:

  • Isothermal sphere (no lumps), r∝ r−2

    • Local density r0~0.3 GeV/c2/cm3 (~1/pint at 100 GeV)

  • Maxwellian (gaussian) velocity distribution

    • Characteristic velocity v0=220 km/s,

    • Local escape velocity vesc=600 km/s

    • Earth velocity vE=232 km/s

  • H. Araújo


    Elastic scattering rates1
    Elastic scattering rates

    • Coupling to protons and neutrons more useful than coupling to nucleus

      • To compare different target materials, indirect searches, LHC results

    • Spin-independent (scalar) interaction

      • note A2 in enhancement factor

      • cMSSM-favoured XS within reach of current detectors

    • Spin-dependent (axial-vector) interaction

      • note J (nuclear spin) instead of A2 enhancement

      • cMSSM-favoured XS out of reach for the time being…

    H. Araújo



    The experimental challenge
    The experimental challenge

    • Low-energy particle detection is easy ;)

      E.g. Microcalorimetry with Superconducting TES

      Detection of keV particles/photons with eV FWHM!

    • Rare event searches are also easy ;)

      E.g. Super-Kamiokande contains 50 kT water

      Cut to ~20 kT fiducial mass (self-shielding)

    • But doing both is hard!

      Small is better for collecting signal

      Large is better for background

    • Ah: and there is no trigger…

    H. Araújo


    Building a wimp detector

    Consider 1 kg target

    Sensitive to Edep>1 keV

    Expected WIMP rates

    0.1−0.000001 evt/day

    However…

    Cosmic rays, a, b, g-rays

    >1,000,000 evt/day

    Neutrons are THE background!

    Several evt/day

    m

    b

    g

    n

    a

    Building a WIMP detector

    WIMP

    1 kg

    H. Araújo


    Building a wimp detector1

    Move underground

    Use radio-pure materials

    Shield external g-rays

    Shield external neutrons

    Actively veto neutrons

    Discriminate e-recoils (g, b) from n-recoils (WIMPs, n)

    Building a WIMP detector

    WIMP

    H. Araújo


    Nuclear recoils backgrounds
    Nuclear recoils - backgrounds

    • Nuclear recoils – same signature

      • Neutrons from (a,n) and SFissionfrom U/Th trace contamination

        • Laboratory walls, shields, vessels, components, target material

      • Neutrons from atmospheric muon spallation

        • Difficult to shield completely even underground

      • Recoils from alpha emitters (e.g. Rn-222 and progeny)

        • Contaminating active target bulk/surfaces, air, etc

      • Eventually, even coherent neutrino scattering

    • Electron recoils – discrimination power is limited

      • Gamma-ray background external to target

        • K-40, Cs-137, U/Th from walls, shields, vessels, components

      • Contamination of target bulk and surfaces

        • U/Th betas and gammas (Pb-214, Bi-214, Pb-210,…)

        • Cosmogenic (Ge-68, Ge-71,…), anthropogenic (Kr-85, Cs-137,…)

    H. Araújo


    Nuclear recoils signal acceptance

    laboratory system

    incoming

    neutron

    En

    q

    nuclear

    recoil

    ER

    En

    Nuclear recoils - signal acceptance

    Ge (CDMS-II)

    • 100 GeV WIMP on Xe (A=131):

    • 220 km/s WIMP → ER,max = 40 keV

    • 1 MeV neutron → ER,max = 30 keV

    • Neutron elastic scattering populates WIMP acceptance region

      • Calibration of detection efficiency with Am-Be (a,n), Cf-252 (SF), D-D, D-T

    • But there are complications:

      • Multi-element: in CaWO4 (CRESST), WIMPs couple mainly to heaviest material (W), but neutrons scatter mainly off lightest (O). Signal acceptance must be calibrated indirectly

      • Quenching factor: in noble liquids (ZEPLIN,XENON,WARP,ARDM,…) conversion from “electron-equivalent” to nuclear recoil energy is not straightforward (or favourable…)

      • Droplets: in C4F10 superheated droplets (SIMPLE,PICASSO) phase transition is independent of energy. Calibration of signal acceptance threshold only

    H. Araújo


    Discrimination single channels

    ionisation

    Q

    L

    scintillation

    H

    phonons

    Discrimination: single channels

    Ionisation Detectors

    Targets: Ge, Si, CS2, CdTe

    CoGeNT, DRIFT, GENIUS,

    HDMS, IGEX, NEWAGE

    Scintillators

    Targets: NaI, Xe, Ar

    ANAIS, CLEAN, DAMA,

    DEAP, KIMS, LIBRA,

    NAIAD, XMASS, ZEPLIN-I

    Bolometers

    Targets: Ge, Si, Al2O3, TeO2

    CRESST-I, CUORE, CUORICINO

    Bubbles & Droplets

    CF3Br, CF3I, C3F8, C4F10

    COUPP, PICASSO, SIMPLE

    H. Araújo


    ionisation

    Q

    L

    scintillation

    H

    phonons

    Discrimination: hybrid detectors

    Heat & Ionisation Bolometers

    Targets: Ge,Si

    CDMS, EDELWEISS

    cryogenic (<50 mK)

    Light & Ionisation Detectors

    Targets: Xe, Ar

    ArDM, LUX, WARP,

    XENON, ZEPLIN

    cold (LN2)

    Light & Heat Bolometers

    Targets: CaWO4, BGO, Al2O3

    CRESST, ROSEBUD

    cryogenic (<50 mK)

    All 3 hybrid technologies

    > 99.9% discrimination

    @ >10 keV NR energy

    H. Araújo


    Phonons microcalorimetry
    Phonons (microcalorimetry)

    Cryogenic: T0~50 mK

    Thermal phonon signal is lost with increasing mass:

    must collect phonons before they thermalise in absorber

    • Superconducting Transition-Edge Sensor (as in CDMS)

    • Collect high-frequency (athermal) phonons from particle interaction

    • Into superconducting Al contacts (threshold 2DAl~ meV)

    • Quasiparticles from broken Cooper pairs diffuse into a W TES

    • SQUID readout offers extremely high sensitivity

    • Channel threshold: 1 keV for Ge & Si nuclear recoils

    J. Cooley, CDMS Collaboration

    H. Araújo


    Scintillation photomultipliers
    Scintillation (photomultipliers)

    DAMA/LIBRA Collaboration

    Room temperature, cold or cryogenic

    NaI, CsI, CaWO4, LXe, LAr: many materials scintillate…

    Photomultipliers: ancient vacuum tube technology,

    but no-one has come up with a better alternative yet

    (and we’re trying…)

    • Scintillation detectors (as in DAMA)

    • Best photomultipliers now approaching 50% quantum efficiency

    • Best NaI(Tl) crystals yield ~90 photons/keV for gamma rays

    • Typically require coincidence of two photomultipliers (2 phe)

    • Threshold: 0.3-3 keV for I nuclear recoils

    • (depending on “channelling” effect)

    H. Araújo


    Ionisation electroluminescence tes hemt jfet

    S2

    (electroluminescence)

    Ionisation(Electroluminescence, TES, HEMT, JFET)

    Cold: T0~200 K

    Difficult to measure one electron, but not so hard to measure electroluminescence photons from one electron

    • Two-phase xenon detectors (as in ZEPLIN)

    • Strong electric field across liquid-gas xenon target

    • Collect ionisation from particle track in liquid Xe

    • Drift up to surface, then emit into vapour phase

    • Electroluminescence photons detected with photomultipliers

    • Threshold: 0.2 keV for Xe nuclear recoils

    1e

    Edwards et al., Astroparticle Phys. 30 (2008) 54

    H. Araújo


    A few examples not comprehensive and somewhat uk centric
    A few examples(not comprehensive and somewhat UK-centric)

    H. Araújo


    Cresst scintillation phonons
    CRESST: Scintillation & Phonons

    Target: 0.6 kg CaWO4

    3 events observed in

    10-40 keVnr acceptance region

    48 kg·days exposure (2007)

    Angloher et al, Astropart. Phys. 31 (2009) 270

    H. Araújo


    Zeplin iii scintillation ionisation
    ZEPLIN-III: Scintillation & Ionisation

    Target: 12 kg LXe

    7 events observed in

    10-30 keVnr acceptance region

    850 kg·days raw exposure (2008)

    (likely e-recoil background)

    Lebedenko et al, PRD 80 (2009) 052010

    H. Araújo


    Cdms ii ionisation phonons
    CDMS-II: Ionisation & Phonons

    Target: 4.4 kg Ge, 1.1 kg Si

    2 events observed in

    10-100 keVnr acceptance region

    612 kg·days exposure (2007-08)

    Background estimate 0.8±0.2!

    Ahmed et al, arXiv:0912.3592

    H. Araújo

    J. Cooley, CDMS Collaboration


    Dama libra scintillation
    DAMA/LIBRA: Scintillation

    Target: 250 kg NaI(Tl)

    8.9s CL modulation

    over 13 annual cycles

    Barnabei et al, arXiv:1002.1028

    (But what is modulated?

    and is it getting smaller?)

    H. Araújo


    Drift ni gas tpc
    DRIFT – NI Gas TPC

    Target: 167 g/m3 CS2 (now CS2+CF4)

    Unlikely that backgrounds mimic signal which appears as forward/backward asymmetry in galactic coordinates

    H. Araújo


    Picasso superheated c 4 f 10
    PICASSO: Superheated C4F10

    Target: 65+69 g C4F10

    H. Araújo


    Cogent ionisation p type point contact ppc hpge
    CoGeNT - Ionisationp-type point contact (PPC) HPGe

    Target: 330 g Ge

    Excess at low energies – a glimmer?

    Aalseth et al, arXiv:1002:4703v2)

    No discrimination, too close to threshold…

    H. Araújo




    World status prospects idm
    World status & prospects (iDM)

    Schmidt-Hoberg & Winkler, JCAP09(2009)010

    Akimov et al., arXiv:1003.5626 (ZEPLIN-III)

    H. Araújo


    Next generation a view
    Next generation: a view

    TWO-PHASE ARGON

    • A=40, <ER>= 13 keV @50 GeV/c2, 35 keV @500 GeV/c2

    • very scalable (cheap, large LAr systems demonstrated)

    • poor energy threshold, low atomic weight, Ar-39 background

    • WARP, ArDM, (DEAP/CLEAN) working on 0.1—1 tonne targets

    • 5-tonne system within 5 years is (optimistically) possible

      CRYOGENIC GERMANIUM

    • A=73, <ER>= 13 keV @50 GeV/c2, 57 keV @500 GeV/c2

    • excellent energy resolution, excellent discrimination

    • difficult to scale (small detector modules, <50 mK cryostats)

    • CDMS, EDELWEISS, (CRESST) working on 10—20 kg targets

    • EURECA and SuperCDMS propose ~100 kg target in 5 years

      TWO-PHASE XENON

    • A=131, <ER>= 11 keV @50 GeV/c2, 85 keV @500 GeV/c2

    • scalable, low threshold

    • control of xenon purity to <ppb is demanding

    • ZEPLIN-III, XENON100, LUX350, (XMASS), working on 10-100 kg

    • XENON1T and LUX-ZEPLIN propose 1 tonne two-phase xenon targets

    Proposals (>1 tonne)

    CDEX, CLEAN, COUPP+, DAMA+, DARKSIDE, DARWIN, DEAP3600, DRIFT, EURECA, GEODM, KIMS+, LUX-ZEPLIN, MAX, SuperCDMS, XMASS, …

    H. Araújo


    Next generation a view1
    Next generation: a view

    Araujo, Strigari & Trotta

    Araujo, Strigari & Trotta

    H. Araújo


    Ready to scale up
    Ready to scale up!

    Pack ?

    UK pioneered several search technologies

    NaIAD, ZEPLIN-I, DRIFT-I, CRESST-I, ZEPLIN-II, DRIFT-II, CRESST-II, ZEPLIN-III, ArDM, EDELWEISS, (EURECA, LZ)

    And pushed forward “underground science”

    Dating back to Holborn Station Laboratory…

    Creating the Boulby Underground Laboratory

    (see Sean Paling’s talk tomorrow)

    But we’re running out of road…

    H. Araújo



    ad