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The self-annihilation cross section

Upper Bound on the Dark Matter Annihilation Cross Section Gregory Mack CCAPP/The Ohio State University. The self-annihilation cross section. How large can the self-annihilation cross section be? That’s the question to ask Most often assumed – “natural scale” 3 x 10 -26 cm 3 /s.

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The self-annihilation cross section

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  1. Upper Bound on the Dark Matter Annihilation Cross SectionGregory MackCCAPP/The Ohio State University

  2. The self-annihilation cross section • How large can the self-annihilation cross section be? • That’s the question to ask • Most often assumed – “natural scale” • 3 x 10-26 cm3/s

  3. Early playing field • First: Unitarity • Limit from Q.M. • The probabilities for elastic and inelastic scattering must sum to 1 • Unitarity of the scattering matrix

  4. Early playing field • Second: KKT • Take a cuspy profile and turn it into a core • KKT would need a BR of about 10-10 to not be seen in monoenergetic photons • Say it must be “invisible particles”

  5. No invisible products: essentially two classes of annihilation products • Photons (direct or eventual) • Hadrons  pions  photons • Charged leptons  radiative loss/internal brehmsstrahlung • Gauge bosons  charged leptons • Monoenergetic Photons • Neutrinos • Sum of probabilities = 100% • Compare background fluxes to theoretical signals

  6. Theoretical Signals • Depends on if you’re looking at: • diffuse contribution from all galaxies • Need to integrate over redshift and include the fact that dark matter is clumped in galaxies • Galactic halo (at some angle from GC) • External galaxy (M 31) • DM halo line-of-sight int. • DEPENDS ON PROFILE

  7. Regardless, divide background into energy bins to look Neutrinos Atmospheric neutrino background. Photons INTEGRAL, COMPTEL, EGRET, CELESTE, HESS, HEGRA

  8. Combined constraint for 2 photons • Results for Kravtsov profile (NFW = lighter) • Wide range of masses • Limit takes the most stringent value at each mass

  9. TOTAL cross section limits • Wide-ranging model-indep. limit • Conservative, comprehensive • Gamma limit is comparable to Neutrino Mack, Beacom, Bell, Jacques, Yüksel Astro-ph/0803.0157v2 (PRD)

  10. More cross section limits • New limits on photons coming from internal brehmsstrahlung from charged leptons • Bell and Jacques • Astro-ph/0811.0821v1

  11. More cross section limits

  12. Conclusions • We have the capability to make statements about the amount of annihilation dark matter experiences • General, comprehensive limits • Better data means tighter constraints

  13. Extra Slides

  14. Distribution Moore NFW • Different profiles  different inner behavior • Moore ρ ~ 1/r1.5 • NFW 1/r1.0 • Kravtsov 1/r0.4 Kravtsov

  15. Integral over redshift. The spectrum of neutrinos depends on the redshift n2

  16. Theoretical flux calculations – Analysis Methods • Line of sight integral – angular radius ψ • Average over a cone of half-angle ψ • Note: This was done by Yüksel, Horiuchi, Beacom, and Ando to modify our neutrino bound for the Milky Way

  17. Atmospheric Neutrino Background • AMANDA and SK data support the non-existence of a signal from DM annih. Ashie, et al (Super-K) PRD 71, 112005 (2005), Fully-contained events Munich (AMANDA), astro-ph/0509330

  18. J dependence on profile • YHBA figure Moore NFW Kravtsov

  19. Background subtraction • J delta’s minus specific J(psi) • HESS • INTEGRAL

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