Dark Matter Searches Dark Matter Searches

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    Dark Matter SearchesDark Matter Searches

    Katherine FreeseMichigan Center for Theoretical Physics

    University of Michigan

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    Vera RubinVera Rubin

    Studied rotation curves

    of galaxies, and found

    that they are FLAT

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    95% of the matter in galaxies is95% of the matter in galaxies is

    unknown dark matterunknown dark matter Rotation Curves of Galaxies:Rotation Curves of Galaxies:

    EXPECTED

    FROM STARS

    OBSERVED:FLAT ROTATION

    CURVE

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    Good news: cosmologists

    don't need to "invent" newparticle:

    Weakly Interacting

    Massive Particles

    (WIMPS). e.g.,neutralinos

    Axions

    ma~10-(3-6) eV

    arises in Peccei-Quinn

    solution to strong-CP

    problem

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    THE BEGINNINGS OF

    DARK MATTERPARTICLE

    PHENOMENOLOGY

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    Axion detector

    (axion to photon conversion)

    Pierre Sikivie

    PRL 51 (1983) p. 1415

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    Axion masses

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    Overall status of axion bounds

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    The WIMP Miracle

    Weakly Interacting Massive Particles are the bestmotivated dark matter candidates, e.g.: LightestSupersymmetric Particles (such as neutralino) are theirown antipartners. Annihilation rate in the early universe

    determines the density today. The annihilation rate comes purely from particle physicsand automatically gives the right answer for the relicdensity!

    This is the mass fraction of WIMPs today, and givesthe right answer (23%) if the dark matter is weakly

    interacting

    h2

    =

    31027

    cm3/sec

    ann

    WIMP mass: GeV 10 TeV

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    WIMP Dark Matter

    Phenomenology: History Looking for neutrinos (Drukier and Stodolsky)

    First paper suggesting direct detection: Goodman and

    Witten 1986 Second paper on direct detection: we

    (I) took into account WIMP distribution in galaxy and (ii)suggested annual modulation (Drukier, Freese, and

    Spergel 1986). A followup paper (Freese, Frieman, Gould 1988)

    suggested using annual modulation to pull out signalfrom background. This is how the only current claimfor direct detection was done (DAMA experiment).

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    Drukier and Stodolsky

    (1984)proposed MeV neutrino detection via elasticscattering off nuclei with 100 eV recoil energy

    Andrzej

    Drukier

    Leo Stodolsky

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    GOODMAN AND WITTEN (1986)

    turned same approach to DMdetection

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    Drukier, Freese, & Spergel (1986)

    i) included model for galactic halo,

    ii) proposed annual modulation, iii)

    SI/SD for various detector elements

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    EXCITING TIMES

    We made WIMP proposals twenty years

    ago:

    It is coming to fruition!

    My personal prediction: one of the

    anomalous results is right and we will

    know very soon.

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    LHC-Making DM

    Coming Soon(We hope)

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    Supersymmetric Particles in LHC Signature: missing energy when SUSY particle is

    created and some energy leaves the detector

    Problem with identification: degeneracy ofinterpretation

    SUSY can be found, but, you still dont know howlong the particle lives: fractions of a second to leavedetector or the age of the universe if it is dark matter

    Proof that the dark matter has been found requiresastrophysical particles to be found

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    Direct Detection of WIMP dark

    matterA WIMP in the Galaxy

    travels through our

    detectors. It hits a

    nucleus, and depositsa tiny amount of

    energy. The nucleus

    recoils, and we detect

    this energy deposit.

    Expected Rate: less than one count/kg/day!

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    Event rate

    dR

    dE

    =

    NT

    MT

    d

    dE

    nv f(v, t)d3v

    (number of events)/(kg of detector)/(keV of recoil energy)

    =

    0F2 (q)

    2m2

    f(v, t)

    vd

    3v

    v> ME/ 22

    Spin-independent

    Spin-dependent

    0=A22

    p2

    p

    0=4

    2

    Sp

    Gp + Sn Gn

    2

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    From DM Tools Website

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    Many claims/hints of WIMPdark matter detection: how

    can we be sure?

    1) The DAMA annual modulation

    2) The HEAT, PAMELA, and ATIC positronexcess

    3) Gamma-rays from Galactic Center 4) WMAP Haze

    HAS DARK MATTER BEENDISCOVERED?

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    The DAMA

    AnnualModulation

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    DAMA annual modulationDrukier, Freese, and Spergel (PRD 1986);Freese, Frieman, and Gould (PRD 1988)

    Data do show a 8 modulation

    WIMP interpretation???

    Bernabei et al 2003

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    DAMA/LIBRA

    (April 17,2008)

    8 sigma

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    Can the positive signal in DAMA

    be compatible with null resultsfrom other experiments?

    Savage, Gelmini, Gondolo, and Freese, arxiv:0808:3607(see also papers by Hooper and Zurek; Fairbairn and Schwetz;

    Chang, Pierce and Weiner 2008)

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    Small remaining region at 10 GeV WIMP mass

    DAMA: spin independent?

    DAMA

    XENON

    CDMS

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    DAMA and

    Spin-

    dependent

    cross sections

    Savage, Gelmini,

    Gondolo, Freese

    0808:3607

    Remaining window

    around 10 GeV.

    Removing SuperK:

    WIMP mass

    up to 20 GeV

    allowed

    DAMA

    SUPER-K

    XENON

    CDMS

    Hooper and Zurek extended Super-K bounds

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    New measurements of Suns

    velocity relative to Halo:250 km/sec (not 220 km/sec)

    All curves movethe left:

    Remaining

    window moves to

    7-8 GeV at 3

    sigma (5-15 for

    SD)

    CRESST

    Savage, Freese, Gondolo, Spolyar 2009

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    Low mass window: COUPP,KIMS,

    COGENT, PICASSO, CRESST

    COUPP

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    COUPP bounds (2007)COUPP bounds (2007)

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    Preview of UC talks:Preview of UC talks:

    COUPP (Eric Dahl, Friday) CoGeNT (Juan Collar, Friday)

    Demonstration of acoustic discrimination.

    Elimination of wall events. Commissioning of COUPP-60 kg.Commissioning of COUPP-60 kg. New spin-dependent limits (4 kg chamber).New spin-dependent limits (4 kg chamber).

    Demonstration of surface event rejection.

    First results from runs in Soudan. Prospects forProspects for PPCsPPCs in DM detection and beyond.in DM detection and beyond.

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    To reconcile DAMA with null

    results from other experiements: Popular theory:

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    To reconcile DAMA with null

    results of other experiments: Popular theory:

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    Direct Detection

    In past two years, two orders of magnitudeincrease in sensitivity (the following results not

    included in our compatibility study):

    (i) CDMS

    (ii) XENON-10

    (iii) ZEPLIN III

    New technology: liquid noble gases

    XENON, LUX, XMASS

    WARP (argon)

    DEAPCLEAN (argon and neon)

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    ZEPLIN III (in Boulby mine)

    Pink: XENON 10

    Black: Zeplin IIIBlue: CDMS II

    See talk of N. Smith

    Future: ZEPLIN and LUX will join forces in DUSEL

    (August 2009

    First science run)

    Second science

    Run to begin

    soon weeks

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    Electron recoils

    Nuclear Recoils

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