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  1. Charged Cosmic Rays And Particle Dark Matter Dan Hooper Fermilab Theoretical Astrophysics Group Fermilab Colloquium April 22, 2009

  2. Current Status Dan Hooper - Charged Cosmic Rays And Particle Dark Matter

  3. Evidence For Dark Matter Dan Hooper - Charged Cosmic Rays And Particle Dark Matter

  4. Evidence For Dark Matter • Galactic rotation curves Dan Hooper - Charged Cosmic Rays And Particle Dark Matter

  5. Evidence For Dark Matter • Galactic rotation curves • Gravitational lensing Hubble Deep Field Dan Hooper - Charged Cosmic Rays And Particle Dark Matter

  6. Evidence For Dark Matter • Galactic rotation curves • Gravitational lensing • Light element abundances -Big Bang Nucleosynthesis yieldsBh2 ~ 0.01-0.02 -Total matter density is much larger, Mh2 ~ 0.13 Dan Hooper - Charged Cosmic Rays And Particle Dark Matter

  7. Evidence For Dark Matter • Galactic rotation curves • Gravitational lensing • Light element abundances • Cosmic microwave background anisotropies • Large scale structure Dan Hooper - Charged Cosmic Rays And Particle Dark Matter

  8. Evidence For Dark Matter • There exists a wide variety of independent indications that dark matter exists • Each of these observations infer dark matter’s presence through its gravitational influence • Still no observations of dark matter’s electroweak interactions (or other non-gravitational interactions) Dan Hooper - Charged Cosmic Rays And Particle Dark Matter

  9. Evidence For Dark Matter • There exists a wide variety of independent indications that dark matter exists • Each of these observations infer dark matter’s presence through its gravitational influence • Still no observations of dark matter’s electroweak interactions (or other non-gravitational interactions) Instead of dark matter, might we not understand gravity? Dan Hooper - Charged Cosmic Rays And Particle Dark Matter

  10. NASA/Chandra Press Release, August 21, 2006 Dan Hooper - Charged Cosmic Rays And Particle Dark Matter

  11. Baryonic matter (hot gas) NASA/Chandra Press Release, August 21, 2006 Dan Hooper - Charged Cosmic Rays And Particle Dark Matter

  12. Baryonic matter (hot gas) Total Mass NASA/Chandra Press Release, August 21, 2006 Dan Hooper - Charged Cosmic Rays And Particle Dark Matter

  13. But What Is The Dark Matter?

  14. But What Is The Dark Matter?

  15. Why WIMPs? • The thermal abundance of a WIMP • T >> M, WIMPs in thermal equilibrium • T < M, number density becomes Boltzmann suppressed • T ~ M/20, Hubble expansion dominates over annihilations; freeze-out occurs • Precise temperature at which freeze-out occurs, and the density which results, depends on the WIMP’s annihilation cross section Dan Hooper - Charged Cosmic Rays And Particle Dark Matter

  16. Why WIMPs? • The thermal abundance of a WIMP • As a result of the thermal freeze-out process, a relic density of WIMPs is left behind: •  h2 ~ xF / <v> • For a GeV-TeV mass particle, to obtain a thermal abundance equal to the observed dark matter density, we need an annihilation cross section of: • <v> ~ pb • Generic weak interaction yields: • <v> ~ 2 (100 GeV)-2 ~ pb Dan Hooper - Charged Cosmic Rays And Particle Dark Matter

  17. Why WIMPs? • The thermal abundance of a WIMP • As a result of the thermal freeze-out process, a relic density of WIMPs is left behind: •  h2 ~ xF / <v> • For a GeV-TeV mass particle, to obtain a thermal abundance equal to the observed dark matter density, we need an annihilation cross section of: • <v> ~ pb • Generic weak interaction yields: • <v> ~ 2 (100 GeV)-2 ~ pb Numerical coincidence? Or an indication that dark matter originates from electroweak-scale physics? Dan Hooper - Charged Cosmic Rays And Particle Dark Matter

  18. WIMP Hunting • Direct Detection • Indirect Detection • Collider Searches Dan Hooper - Charged Cosmic Rays And Particle Dark Matter

  19. WIMP Annihilation Typical final states include heavy fermions, gauge or Higgs bosons  The Indirect Detection of Dark Matter W- W+ Dan Hooper - Charged Cosmic Rays And Particle Dark Matter

  20. WIMP Annihilation Typical final states include heavy fermions, gauge or Higgs bosons Fragmentation/DecayAnnihilation products decay and/or fragment into combinations of electrons, protons, deuterium, neutrinos and gamma-rays  The Indirect Detection of Dark Matter W- q W+ q  e+ 0 p   Dan Hooper - Charged Cosmic Rays And Particle Dark Matter

  21. WIMP Annihilation Typical final states include heavy fermions, gauge or Higgs bosons Fragmentation/DecayAnnihilation products decay and/or fragment into combinations of electrons, protons, deuterium, neutrinos and gamma-rays Synchrotron and Inverse Compton Relativistic electrons up-scatter starlight/CMB to MeV-GeV energies, and emit synchrotron photons via interactions with magnetic fields  The Indirect Detection of Dark Matter W- q W+ q  e+ 0 p    e+ Dan Hooper - Charged Cosmic Rays And Particle Dark Matter

  22. Neutrinos from annihilations in the core of the Sun • Gamma Rays from annihilations in the galactic halo, near the galactic center, in dwarf galaxies, etc. • Positrons/Antiprotons from annihilations throughout the galactic halo • Synchrotron Radiation from electron/positron interactions with the magnetic fields of the inner galaxy The Indirect Detection of Dark Matter Dan Hooper - Charged Cosmic Rays And Particle Dark Matter

  23. Dark Matter With Charged Cosmic Rays • WIMP annihilation products fragment and decay, generating equal numbers of electrons and positrons, and of protons and antiprotons • Charged particles move under the influence of the Galactic Magnetic Field; Electrons/positrons lose energy via synchrotron and inverse Compton scattering • Astrophysical sources are generally expected to produce far more matter than antimatter; large positron/antiproton content in the cosmic ray spectrum could provide evidence for dark matter Dan Hooper - Charged Cosmic Rays And Particle Dark Matter

  24. Charged Particle Astrophysics With Pamela • Major step forward in sensitivity to GeV-TeV cosmic ray electrons, positrons, protons, antiprotons, and light nuclei • Among other science goals, PAMELA hopes to identify or constrain dark matter annihilations in the Milky Way halo by measuring the cosmic positron and antiproton spectra Dan Hooper - Charged Cosmic Rays And Particle Dark Matter

  25. Charged Particle Astrophysics With Pamela • Combination of tracker and calorimeter enable charge, mass, and energy determinations • Very accurate particle ID Tracker e+ e- Calorimeter p+ Dan Hooper - Charged Cosmic Rays And Particle Dark Matter

  26. Pamela’s New Antiproton Measurement • Best measurement to date • Dramatically smaller error bars above ~1-10 GeV Pamela Collaboration, arXiv:0810.4994 Dan Hooper - Charged Cosmic Rays And Particle Dark Matter

  27. Pamela’s New Antiproton Measurement • Best measurement to date • Dramatically smaller error bars above ~1-10 GeV • The antiprotons detected by Pamela are consistent with being entirely from secondary production (byproduct of cosmic ray propagation) Pamela Collaboration, arXiv:0810.4994 Dan Hooper - Charged Cosmic Rays And Particle Dark Matter

  28. Pamela’s New Positron Measurement Dan Hooper - Charged Cosmic Rays And Particle Dark Matter Pamela Collaboration, arXiv:0810.4995

  29. Pamela’s New Positron Measurement • First glance: • Is this all screwed up? • Charge-dependent solar modulation important below 5-10 GeV! • (Pamela’s sub-10 GeV positrons appear as they should!) Dan Hooper - Charged Cosmic Rays And Particle Dark Matter Pamela Collaboration, arXiv:0810.4995

  30. Pamela’s New Positron Measurement • First glance: • Is this all screwed up? • Charge-dependent solar modulation important below 5-10 GeV! • (Pamela’s sub-10 GeV positrons appear as they should!) Astrophysical expectation (secondary production) Dan Hooper - Charged Cosmic Rays And Particle Dark Matter Pamela Collaboration, arXiv:0810.4995

  31. Pamela’s New Positron Measurement Rapid climb above 10 GeV indicates the presence of a primary source of cosmic ray positrons! • First glance: • Is this all screwed up? • Charge-dependent solar modulation important below 5-10 GeV! • (Pamela’s sub-10 GeV positrons appear as they should!) Astrophysical expectation (secondary production) Dan Hooper - Charged Cosmic Rays And Particle Dark Matter Pamela Collaboration, arXiv:0810.4995

  32. And if you think the Pamela result is surprising…

  33. The New Cosmic Ray Electron Spectrum From ATIC • In a series of balloon flights, ATIC has measured a 4-5 excess of cosmic ray electrons between 300 and 800 GeV (Nature, Nov. 21, 2008) • This requires a local source of cosmic ray electrons/positrons (within ~1 kpc) • If we extrapolate the Pamela positron fraction up to higher energies, the ATIC result approximately matches Dan Hooper - Charged Cosmic Rays And Particle Dark Matter

  34. WMAP and Energetic Electrons/Positrons • WMAP does not only detect CMB photons, but also a number of galactic foregrounds • GeV-TeV electrons emit hard synchrotron in the frequency range of WMAP Thermal Dust Soft Synchrotron (SNe) WMAP Free-Free Dan Hooper - Charged Cosmic Rays And Particle Dark Matter

  35. Synchrotron + Free-free = + T & S Dust WMAP + CMB

  36. Synchrotron + Free-free = + T & S Dust WMAP + Well, actually… No CMB

  37. Synchrotron + Free-free - = … + T & S Dust WMAP + CMB

  38. “The WMAP Haze” 22 GHz

  39. “The WMAP Haze” 22 GHz After known foregrounds are subtracted, an excess appears in the residual maps within the inner ~20 around the Galactic Center

  40. Pamela, ATIC, and WMAP • Highly energetic electrons and positrons are surprisingly common both locally, and in the central kiloparsecs of the Milky Way • Not the product of any plausible propagation mechanism or other such effect (see P. Serpico, arXiv:0810.4846) • Constitutes the discovery of bright sources of e+e- pairs with a very hard spectral index Dan Hooper - Charged Cosmic Rays And Particle Dark Matter

  41. Dark Matter as the Source of the Pamela, ATIC, and WMAP Signals • The distribution and spectrum of the WMAP haze are consistent with being of dark matter origin • The spectral features observed by Pamela and ATIC could also be generated by dark matter annihilations Cholis, Goodenough, Hooper, Simet, Weiner arXiv:0809.1683 Dan Hooper - Charged Cosmic Rays And Particle Dark Matter Hall and Hooper, arXiv:0811.3362

  42. Dark Matter as the Source of the Pamela and ATIC Signals … but not necessarily easily.

  43. Dark Matter as the Source of the Pamela and ATIC Signals … but not necessarily easily. • Challenges Faced Include: • Very hard spectrum Pamela Hooper and J. Silk, PRD, hep-ph/04091040 Dan Hooper - Charged Cosmic Rays And Particle Dark Matter

  44. Dark Matter as the Source of the Pamela and ATIC Signals … but not necessarily easily. • Challenges Faced Include: • Very hard spectrum • Too many antiprotons, gamma rays, synchrotron Pamela Hooper and J. Silk, PRD, hep-ph/04091040 Dan Hooper - Charged Cosmic Rays And Particle Dark Matter

  45. Dark Matter as the Source of the Pamela and ATIC Signals … but not necessarily easily. • Challenges Faced Include: • Very hard spectrum • Too many antiprotons, gamma rays, synchrotron • Requires a very high annihilation rate Pamela Hooper and J. Silk, PRD, hep-ph/04091040 Dan Hooper - Charged Cosmic Rays And Particle Dark Matter

  46. Dark Matter as the Source of the Pamela and ATIC Signals Particle Physics Solutions:

  47. Dark Matter as the Source of the Pamela and ATIC Signals Particle Physics Solutions: Very hard injection spectrum (a large fraction of annihilations to e+e-, +- or +-) Cholis, Goodenough, Hooper, Simet, Weiner arXiv:0809.1683 Dan Hooper - Charged Cosmic Rays And Particle Dark Matter

  48. Dark Matter as the Source of the Pamela and ATIC Signals • Particle Physics Solutions: • Very hard injection spectrum(a large fraction of annihilations to e+e-, +- or +-) • For example, the lightest Kaluza-Klein state in a model with a universal extra dimenison (UED) fits remarkably well (or a KK- or other particle which annihilates to light fermions through a Z) Hooper, K. Zurek, arXiv:0902.0593; Hooper, G. Kribs, PRD, hep-ph/0406026; Dan Hooper - Charged Cosmic Rays And Particle Dark Matter

  49. Dark Matter as the Source of the Pamela and ATIC Signals Particle Physics Solutions: Very hard injection spectrum (a large fraction of annihilations to e+e-, +- or +-) Annihilation rate dramatically increased by non-perturbative effects known as the “Sommerfeld Enhancement” -Very important for m<<mX and vX<<c (such as in the halo, where vx/c~10-3) SM X  X SM SM X   X SM Arkani-Hamed, Finkbeiner, Slatyer, Weiner, arXiv:0810.0713; Cirelli and Strumia, arXiv:0808.3867; Fox and Poppitz, arXiv:0811.0399 Dan Hooper - Charged Cosmic Rays And Particle Dark Matter

  50. Dark Matter as the Source of the Pamela and ATIC Signals Astrophysical Solutions: