X. Wu, DPNC, 18/06/12*Dark Matter Searches in Space

Xin Wu

*Evidence for Dark Matter Visible objects in the universe moves faster than expectedVelocities of stars in the Milky Way (1932, Oort)Velocities of galaxies in clusters (1933, Zwicky)Rotational speeds of galaxies (galactic rotation curves) (1970, Rubin) -> Dark Matter haloGravitational lensingMass-to-light ratios obtained from strong and weak lensing effect correspond to dynamical measurementsThe bullet clusterMass determined by light emission mass determined by motion Dark Mass!No other evidence that the Newton dynamics is invalid at large scales

Dark Matter Searches Dark matter searches rely on interactions between DM and SM particlesHas not yet been seen! X. Wu, DPNC, 02/11/11*Direct searches: DM-SM scatteringLook for nuclear recoil from galactic DM scatteringVery weak signal deep underground, cryogenicAstronomical observations (gravitational probes) continue to explore the nature of the DMIndirect searches: DM-DM annihilating to SM particlesLook for edges/bumps in SM particle spectrums in cosmic rays with ground-based or space observatoriesCollider searches: production of DM particles via SM interactions signature: missing Et (MET) (Johannas analysis in ATLAS)

DPNC participations!

Indirect searches X. Wu, DPNC, 02/11/11*DM-DM annihilations in our galaxy might give detectable signature of SM particlesn, g, e+, antiproton, antinucleiSensitive to high masses and different couplings complementary to direct searcheschallenges: astrophysical background and propagation Annihilation rate r2DM more flux from regions of dense DM: galaxy clusters, galactic center, Sun, earthBUT only neutrino (and somewhat g) can easily escape from these regions Indirect signature depend on DM mass, annihilation cross section, DM-SM couplingsVery model dependent! lots of fun for signal/limit interpretation

Ground-based detectorsLarge acceptance (with arrays)Resolution Is good for very high energies Indirect search experiments X. Wu, DPNC, 02/11/11*Space detectorsCan detect all signatures except nsmall acceptance

Indirect search with neutrinos X. Wu, DPNC, 02/11/11*Ground-based neutrino telescope MACRO, SuperK, ANTARES, AMANDA/IceCube, Detect upward going muons from muon neutrinos interacting in the Earth Setting limits on muon flux or annihilation cross section as function of massModel dependent, typically use MSSM with WW, bb, tt, mm, nn channelss(annihilation) s(scattering) in the Sun because of equilibrium Relate result to direct searches Setting upper limit to s(annihilation) using some models of SUSY and halo profile

Indirect search with gamma-ray X. Wu, DPNC, 02/11/11*Ground-based Imaging Atmospheric Cherenkov telescopes MAGIC, HESS, VERITAS, CTA, sensitive to gs from 50 GeV 50 TeV (>100 TeV for CTA)Gamma-ray space telescopesEGRET, FERMI/LAT, GAMMA-400, sensitive to gs 20 MeV - 300 GeV, excellent pointing, mapping capability Signature: Mono-energetic g-line from direct annihilation or continuum through annihilation into intermediate statessearch in galactic dark matter halo, dwarf galaxies, galaxy clusters, galactic dark matter satellites,

Some results from gamma-ray telescopesX. Wu, DPNC, 02/11/11*Fermi/LAT dwarf galaxy search excluded WIMP below 25 GeV annihilating to b-bbar or t+t-, assume the DarkSUSY models No smoking gun (yet) in Fermi/LAT photon line search constrain the gg and Zg annihilation cross section Ground-based telescope has sensitivity for high energy (multi-TeV) HESS J1745-290

Indirect search with charged particles X. Wu, DPNC, 02/11/11*Annihilation of DM can add extra (stable) antiparticles (e+, pbar, antinuclei) to the cosmic ray but their detection can be done best above the atmospherehigh altitude balloons: BESS, CAPRICE, HEAT, BEST, ATIC, CREAM satellites: PAMELA, GAMMA-400, space station: AMS2, CALET, Not always possible to put a magnet into the spaceLook for structures in total spectra: e++e-, p+pbar, etcChallenge: understand the galactic (charged) cosmic ray background e-/p produced in SN explosion and accelerated in the shocks of the remnants diffused in the galactic magnetic fields (mG): directions randomizedsecondary e+/pbar produced in the collisions of primary proton with matter in the galactic diskprimary cosmic ray has a (broken) power law energy spectrum Charged DM flux is affected by diffusion and, for e, energy loss from synchrotron radiation and inverse Compton scattering on CMB and star-light

X. Wu, DPNC, 02/11/11*Sensitivity reached 100 GeV (PAMELA)In good agreement with cosmic ray models can be used to ruled out some MSSM dark matter modelsAntiproton flux and ratio AMS2 hurry up!

Positron fraction e+/(e++e-) X. Wu, DPNC, 02/11/11*Growing excess above 10 GeVfirst observed in 1970s, confirmed by PAMELA, Fermi/LAT, waiting for AMS2Astrophysical sources?Pulsars? Primary e+?

DM? would require very large annihilation cross section (or boost factor) and leptophilic models in order to to reconcile with the antiproton data of PAMELAIn general not favoredMultiple origins?

remains a great puzzle!

e++e- spectrumX. Wu, DPNC, 02/11/11*bump at ~300-600 GeV reported first by ATIC, also seen by PPB-BETS Fermi/LAT sees more like a hardening at ~100GeV and softening at ~1TeVMore data and new space detectors with thicker calorimeter will help to understand the high energy regionAMS2, CALET, DAMPE,

another puzzle!

DAMPEX. Wu, DPNC, 02/11/11*DAMPE: DArk Matter Particle Explorer Chinese satellite experiment to be launched in 2015, mission time > 3 yearsfinanced by the Chinese Academy of Sciences High energy (GeV 10 TeV) e/g detector to search for DM, also for cosmic ray studies and high energy g-ray astronomyBaseline Detector Design:Si-PIN charge detector (2.5x2.5 cm2) matrix, measure Z up to 20, DZ/Z~ 10% Plastic Scintillatior strip telescope, cross section 2x1 cm2, 2 double layers (X,Y) Interleaved with Tungsten platesBGO imaging calorimeter

305 crystal of 2.5x2.5x60 (cm3) 14 layers, 31 X0 (total 33 X0)multi dynode PMT+VA32 chip

Neutron detector (Boron doped plastic scintillator) for additional e/p separation

DAMPEX. Wu, DPNC, 02/11/11*Detector performance requirement Detection of e/g of 5 GeV-10 TeV, energy resolution 20 Detection of high energy cosmic ray 100 GeV 100 TeV, energy resolution 0.2 cm2sr, p: >0.2 cm2sr Collaborating institutesPurple Mountain Observatory (PMO), NanjingUniversity of Sci. & Tech. of China (USTC), HefeiInstitute of High Energy Physics (IHEP), BeijingInstitute of Modern Physics (IMP), Lanzhou DPNC, Universit de GenveParticipation of DPNC (Xin)Coordination of test beam activities at CERNOct-Nov 2012 on H4 beam, calibration unit ~1/4 of full detectorCalibration and data analysisStepping stone to a more ambitious project

HERDX. Wu, DPNC, 02/11/11*HERD: High Energy cosmic Radiation Detection facility On board of the Chinese Space Station (~2020) Proposed by the same community of the DAMPEMuch bigger GF, better energy and pointing resolutions, sensitive to very high energy cosmic rays (knee region ~1 PeV)Two main goals: DM search and origin of galactic cosmic rays305 crystal of 2.5x2.5x60 (cm3) 14 layers, 31 X0 (total 33 X0)multi dynode PMT+VA32 chip

Neutron detector (Boron doped plastic scintillator) for additional e/p separation s_yqxu 1986bornExcept for L ( ~ 8), PeV spectra feasible with GF~2-3 in several years.P ( ~ 1)He ( ~ 4)L ( ~ 8)M ( ~ 14)H ( ~ 25)VH ( ~ 35) Fe ( ~ 56)1 PeV 10-event sensitivities

HERD conceptual detector designX. Wu, DPNC, 02/11/11*PWOW+ CsI(Na) + Fiber + ICCDCharge detector: Si-PIN (1cm1cm500mm)Top: 2x(1mx1m), 4 Sides: 2x(1mx40cm)Shower TrackerW: 10x3.5mm + 2x17.5mm + 2x35mm (4X0 = 1.6l)Scin. Fibers: 14 X-Y double layers, 1x1mm2, 1m long

Nucleon Tracker with Scin. Fibers

ECAL: 16X0 = 0.7lPWO bar: 2.5x2.5x70cm36 layers alternate in X-Y

HCAL: 30 layers of W plates + CsI cells W: 30x3.5mm, 3X0 = 1.2 lCsI cell:2.5x2.5cm2x0.2cm

Neutron detector: B-doped plastic scintillator with delayed signals

Comparison of missionsX. Wu, DPNC, 02/11/11*The mains goals of the HERD detector design Better energy resolution (e/g), larger geometrical factor (cosmic ray) and high energy reach (e/g and cosmic ray)

HERDDAMPEAMSPAMELAFERMICALETe/g Energy Res. @100GeV1%1.5%3%5%10%2%e/g Ang. Res. @100GeV0.3O0.8O0.3O1.0O0.1O0.3OGeometrical Factor m2sr1-20.30.10.021.00.1e/p discrimination5x106105106104103105Energy range (GeV)0.1-1065-1040.1-1030.1-3000.02-3005-5x103

Current Status of HERD X. Wu, DPNC, 02/11/11*Mission concept (science goals with requirements) selected by JESSA of CAS General Establishment of Space Science and Application, agency in charge of the selection of scientific missionConceptual detector design reviewed in Feb 2012, further technical review final selection decision expected later this yearSimulation and detector optimization are just startedinternational collaborations are welcome at all levelsDPNC (Martin, Xin) have expressed interest in participating in the projectdetector optimization, in particular using Si strips instead of scintillating fibers for the shower trackerECAL and Trigger electronics also potential collaboration areasSwiss Industrial participation Intention well received by GESSA Good contact already exist through POLAR and DAMPEBy associating early, we can hope to play a major role in the project once it is concretized

Conclusions X. Wu, DPNC, 02/11/11*The nature of the DM is on of the most fundamental questions in astronomy, astrophysics, astroparticle physics, cosmology and particle physics There is a small industry of DM search Underground, underwater, under-ice, on the ground, in the space, DPNC has already involved in many of these experiments and a transverse synergy is emerging IceCube, AMS, ATLAS, CTAAlso DPT Can further develop this synergy by participating in the new space based projects (DAMPE and HERD) People interested are very welcome to join

Extra slidesX. Wu, DPNC, 02/11/11*

How much dark matter in the Universe? Can be estimated from observations of clusters of galaxies radial velocities, hot gas distribution, gravitational lensing relic density: WDM ~ 0.2-0.3 (WX rX/rcrit, rcrit : density of a flat Universe)X. Wu, DPNC, 02/11/11*Can be obtained by a global fit of cosmological parameters assuming the standard model of big bang cosmology (LCDM) observations: anisotropy of CMB (WMAP), large-scale structure (galaxy surveys) , Type Ia supernovae survey WL 0.72, WDM 0.23, Wb 0.05

Nature of Dark Matter X. Wu, DPNC, 02/11/11*Dark matter unlikely to be baryonic (MACHOs: Massive Compact Halo Objects)Neutron stars, brown dwarf, planets, primordial black holes ruled out by anisotropy of CMB, large-scale structure and big-bang nucleosynthesis (BBN)Not observed by direct searches with microlesing (MACHO, EROS, OGLE)Dark Matter is unlikely to be hotThermally produced ultrarelativistic particles (m

DM-SM interaction The strength of DM-SM interaction is constrained by the observed present DM relic densityWIMP pair annihilation cross section into SM particles determines the time at which WIMPs dropped out of thermal equilibrium (annihilation rate < expansion rate)

X. Wu, DPNC, 02/11/11* ~1 pb annihilation cross section gives correct relic density timeNumber density

Direct Searches X. Wu, DPNC, 02/11/11*Assume stationary DM halo in the galactic frameThe earth traverses the DM halo at ~23015 km/sAt this speed DM-SM scattering is mainly elasticTypical nuclear recoil energy is ~1-100 keV for WIMP of 10 GeV 10 TeVRecoil energy spectrum is approximately exponentialResulting from the convolution of the Maxwellian distribution of the DM velocity and the model dependent DM-nuclei cross section low threshold detectors (eg. Ge) more sensitive to WIMP of low massCross section depends on the nature of DM-SM couplingSpin-independent (SI) and spin-dependent (SD) SI cross section scales as A2 use heavy target nuclei, eg. XeEvent rate depends on WIMP flux (~rv/M) and scattering cross sectionTypically < 1 event/day/kg need large target and low background site Detection of the recoil energyIonization and/or scintillation and/or heat

(Many) Direct Search ExperimentsX. Wu, DPNC, 02/11/11*Starting from a 0.8 kg Ge ionization detector at Homestake Mine in 1986 sensitivity is reaching ~1 event/100kg/year (for 60 GeV WIMP)From Gaitskell

Examples of direct search experiments X. Wu, DPNC, 02/11/11*Pure germanium detector for ionization detection Homestake, Heidelberg-Moscow, IGEX, (GERDA, MAJORANA)CoGeNT, CDEX/TEXONO: very low energy threshold (sub-keV)CoGeNT observed excess at 7-11 GeVCrystal (NaI) detector for scintillation detection DAMA/LIBRA, NaIAD, DM-Ice DAMA/LIBRA observed annual modulationCryogenic detector for heat (vibration) detection Heat and ionization detection with semiconductor: CDMS, EdelweissHeat detection with CaWO4 crystal: CRESST observed some excessNobel liquid detector for ionization and scintillation detectionZEPLIN, XENON, XMASS, PANDA-X, LUX, ArDM Best DM limit from XENON100 ruled out all positive claims above!TPC to measure the direction of the nuclear recoilsDRIFT, MIMAC, DMTPC,

Current results of direct searches X. Wu, DPNC, 02/11/11*Expressed as contour or excluded region in the WIMP mass cross section plane For fixed density, WIMP flux scales with inverse massSI cross section, normalized to nucleon assuming sN = A2sSI

Collider searches X. Wu, DPNC, 02/11/11*DM can be produced at the colliders if s is sufficientcoupling is unknown, but cross section constrained by DM relic densitysignature is MET (or nothing if pair produced back-to-back!)Two main strategies of searches model search: if a BSM model contains a DM candidate, search for all signatures (typically involving MET) constrain the model constrain DM phenomenology compatibility with the relic densitySUSY, ED, Little Higgs, generic search: look for events with large MET, balanced by one ISR jet/photon constrain rate constrain effective coupling (vector, axial-vector, scalar) constrain DM-nucleon cross section (SI and SD) effective theory is only valid for heavy mediators; light mediators needs to be included explicitly with assumption on their masses (typically better limits for masses 100 GeV)

Results from collider searches X. Wu, DPNC, 02/11/11*Many DM interpretations of collider searches are done by phenomenologists

But experimentalist are catching up fast!

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