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Evidence for WIMP Dark Matter

Evidence for WIMP Dark Matter. Wim de Boer, Marc Herold, Christian Sander, Valery Zhukov Univ. Karlsruhe Alex Gladyshev, Dmitri Kazakov Dubna. Outline (see astro-ph/0408272, hep-ph/0408166) EGRET Data on diffuse Gamma Rays shows excess in all sky directions with the SAME spectrum

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Evidence for WIMP Dark Matter

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  1. Evidence for WIMP Dark Matter Wim de Boer, Marc Herold, Christian Sander, Valery Zhukov Univ. Karlsruhe Alex Gladyshev, Dmitri Kazakov Dubna • Outline (see astro-ph/0408272, hep-ph/0408166) • EGRET Data on diffuse Gamma Rays shows excess in all sky directions with the SAME spectrum • Halo parameters from sky map • WIMP mass from spectrum • Data consistent with Supersymmetry

  2. Cosmologists: What is CDM and Dark Energy made of? Particle physicists: Where are the Supersymmetric Particles? Astrophysicists: What is the origin of excess of diffuse Galactic Gamma Rays? Astronomers: Why a change of slope in the galactic rotation curve at 1.1 R0? Why ring of stars at 14 kpc so stable? Why ring of molecular hydrogen at 4 kpc so stable? Physics Problems

  3. Proposed Solution • DM made of WIMPS annihilating into quarks, which yield hard gammas from 0 decays • Annihilation cross section given by HUBBLE constant! • Gamma excess correlated with ring of stars at 14-18 kpc • thought to originate from infall of a dwarf galaxy • and ring of DM at 4 kpc stabilizes ring of hydrogen • From SPECTRUM of excess of gamma rays DM: • WIMP mass 50-100 GeV • From INTENSITY: halo distribution and rotation curve • WIMP has properties of supersymmetric lightest particle

  4. Expected Profile Observed Profile z xy xy Rotation Curve x FR FG y halo DM 2003, Ibata et al, Yanny et al. disk xz xz bulge Inner Ring Outer Ring Executive Summary Halo profile

  5. WMAP determines WIMP annihilation x-section Thermal equilibrium abundance Actual abundance Boltzmann equation: H-Term takes care of decrease in density by expansion. Right-hand side: Annihilation and Production. Comoving number density T>>M: f+f->M+M; M+M->f+f T<M: M+M->f+f T=M/25: M decouples, stable density (wenn annihilation rate  expansion rate,i.e. =<v>n  H !) Jungmann,Kamionkowski, Griest, PR 1995 Neutralino annihilation is a strong source of antiprotons, positrons and gammas by annihilation into quarks. x=m/T T=M/25 Present number density (h2=0.1130.009)requires <v>=2.10-26 cm3/s assuming no coannihilation

  6.   f f f ~ f    f f f   W Z 0    Z W Neutralino Annihilation Final States Z A B-fragmentation well studied at LEP! Yield and spectra of positrons, gammas and antiprotons well known! Dominant Diagram for WMAP cross section:  +   A  b bbar quark pair

  7. t t t t bb bb Annihilation cross sectionsin m0-m1/2 plane (μ > 0, A0=0) tan=5 tan=50 10-24 10-27 EGRET   WW WW For WMAP x-section of <v>2.10-26 cm3/s one needs large tanβ in bulk region (no coannihilation, no resonances)

  8. Stau coannihilation 0 mA resonance WMAP EGRET EGRET excess interpreted as DM consistent with WMAP, Supergravity and electroweak constraints MSUGRA can fulfill all constraints from WMAP, LEP, b->s, g-2 and EGRET simultaneously, if DM is neutralino with mass in range 50-100 GeV and squarks and sleptons are O(1 TeV)

  9. Excess of Diffuse Gamma Rays above 1 GeV as measured by EGRET satellite (9 yrs of data) B C A Prel. Inv. Compton 0 Bremsstrahlung Strong, Moskalenko, Reimer, to be published D E F A: inner Galaxy (l=±300, |b|<50) B: Galactic plane avoiding A C: Outer Galaxy D: low latitude (10-200) E: intermediate lat. (20-600) F: Galactic poles (60-900)

  10. Local electron and proton spectra determine shape of gamma background No SM No SM Protons Electrons Solar modulation (SM) important below 10 GeV Proton and electron spectra above 10 GeV well measured  Gamma spectrum well known, unless one assumes “local bubble”, i.e. spectra in galaxy different from locally measured ones.

  11. Excess of Diffuse Gamma Rays has same spectrum in all directions compatible with WIMP mass of 50-100 GeV Important: if experiment measures gamma rays down to 0.1 GeV, then normalizations of DM annihihilation and background can both be left free, so one is not sensitive to abso- lute background estimates, BUT ONLY TO THE SHAPE, which is much better known.

  12. Diffuse Gamma Rays for different sky regions A B C D E F DMA  Boostfactor <2> If boost factor, i.e. clustering, similar in all directions, then signal strength determines DM density 

  13. Why LIGHT traces DM in disc • Reasons for enhanced DM in plane of galaxy: • Adiabatic compression of halo by gravity from disc • (Blumenthal, Kalnajs, Wilkinson,…..) • (halo distribution may be modified by resonant interactions • between bar and halo, Athanassoula, Weinberg,..) • 2) Anisotropic infall along filaments of DM • (e.g. ring of stars at 14-18 kpc thought to originate • from infall of dwarf galaxy (Yanny et al., Ibata et al., …) Parametrize with at least 2 rings: Inner ring for 1) Outer ring for 2)

  14. H H2 4 R [kpc] Fit results of halo parameters Gamma Ray Flux: (<v> from WMAP) 2 rings with maximum intensity at 4 and 14 kpc Enhancement over isothermal profile 3 and 8, respectively Sensitive to radius, because Sun OFF CENTER! Halo Parameters: (assuming boost fct Bl same in all directions, comes out B>20) 14 kpc coincides with ring of stars at 14-18 kpc due to infall of dwarf galaxy (Yanny, Ibata, …..) 4 kpc coincides with ring of neutral hydrogen molecules!

  15. Halo profiles Isothermal cored profile NFW cuspy profile WITH rings WITH rings WITHOUT rings WITHOUT rings 100 10

  16. Longitude fits for isothermal (cored) profile WITH 2 rings WITH 2 rings WITHOUT rings WITHOUT rings DISC 100<b<200 100<b<200 DISC 200<b<900 200<b<900 50<b<100 50<b<100 Halo parameters from fit to 180 sky directions: 4 long. profiles for latitudes <50, 50<b<100, 100<b<200, 200<b<900 (=4x45=180 directions)

  17. Latitude fits for isoth. Profile with |long|<300 0.1 < E < 0.5 GeV E > 0.5 GeV

  18. y b a x c z EGRET data compatible with prolate isothermal halo profile with b/a  0.9, c/a  0.8 define the slope 0 - local density 0.3-0.7 GeV/cm3 a -scale parameter (depends on 0) Isothermal profile: ,β,,a = 2,2,0,4 NFW cusp W. de Boer et al., astro-ph/0408272 Isothermal core Preferred structure (Bailin, Steinmetz,astro-ph/0408163 Ellipsoid: x2/a2 +y2/b2 + z2/c2 = c

  19. FR FG halo DM bulge disk Inner Ring Outer Ring Rotation curve of our galaxy Rotation curve shows there is a ring of CDM with a mass of a few 1010 Mסּ

  20. Local surface density Σ Height distribution and velocity dispersion  of local stars determine local gravitational potential (just like decrease in atmospheric density is determined by gravity of earth). Decrease in rotation curve suggests little Dark Matter. First measurements: van Oort in 1932: assuming constant : repulsive gravity. Later: (z )  E.g. Σ= ∫dz = 716 Mסּ/pc-2 for zmax=1.1 kpc by Kuijken+ Gilmore, 1991. They assumed constant DM density and very little of it. So they were stretching visible matter by brown dwarfs etc. 2001: Olling +Merrifield: consensus value of Σ from visible matter: 3510 2002: Bienayme et al.: Σ = 85? Error strongly dependent on assumptions of DM distributions. 2004: de Boer et al.: ΣDM=60 Σbaryonic=30 Mסּ/pc-2with steeply varying DM density steep function of z (on slope of ring!)

  21. Positron fraction and antiprotons from DM annihilation Positrons Positrons Antiprotons Antiprotons SAME Halo and WIMP parameters as for GAMMA RAYS but fluxes strong function of propagation models!

  22. SUSY Mass spectra in mSUGRA Charginos, neutralinos and gluinos light LSP largely Bino  DM may be supersymmetric partner of CMB

  23. Supersymmetry at linear collider pb x-section! Karl Ecklund, Cornell

  24. Supersymmetry at proton collider Silke Duensing Typical cross-sections (pb) m [GeV] pb x-section with very little background!

  25. Summary 1. Significant Excess (>10) of EGRET diffuse gamma ray data has SAME shape in all sky directions, as expected for DM. 2. Excess outside disk follows cored (isothermal) halo profile, NO CUSP • 3. Independent evidence that EGRET excess indeed originates from • DM annihilation follows from: • Strong signal from region with ring of stars at 14-18 kpc, • thought to be tidally disrupted dwarf galaxy • b) Strong signal from region with ring of molecul. hydrogen at 4 kpc • c) Gamma ray data used to predict rotation curve! • d) Orientation of disc along MINOR axis of prolate halo (as pred.) • e) Large local surface density 4. Alternative “conventional” models cannot explain stability of ring of stars at 14 kpc and H2 ring of molecular gas at 4 kpc, nor change of slope of rotation curve, nor halo shape of excess, nor high local surface density

  26. Summary of summary EGRET galactic gamma ray data provides intriguing hint that - since WIMP has properties of a spin ½ photon - DM is the Supersymmetric Partner of the CMB This conclusion is INDEPENDENT of the absolute normalization, only dependent on the SHAPE of diffuse gamma ray spectrum!

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