25 January 2007

Speaker: Douglas Finkbeiner (CfA)

Title: "Exciting" Dark Matter and the 511 keV line.

Abstract: Weakly-interacting massive particle (WIMP) dark matter has been invoked to explain excess GeV gamma-rays, high-energy positrons, and even excess microwaves in the inner Milky Way. Until now, however, there has been no connection between these weak scale (mass of ~ 300 GeV) WIMPs and the 511 keV e+/e- annihilation radiation from the inner Milky Way. Neal Weiner and I have proposed a WIMP candidate with an "excited state" 1-2 MeV above the ground state (known as "exciting" dark matter, eDM). This state may be collisionally excited and decays by e+/e- pair emission. Such a particle converts WIMP kinetic energy into pairs, which in turn could produce a substantial fraction of the 511 keV line observed by INTEGRAL/SPI in the inner Milky Way. Only a small fraction of the WIMPs are above threshold, and that fraction drops sharply with Galactocentric radius, naturally yielding a radial cutoff, as observed. Even if the scattering probability in the inner kpc is much less than 1% per Hubble time, enough power is available to produce the number of pairs per second observed. I will specify the parameters required to explain the INTEGRAL result, and discuss other observational consequences of this model.

Video of the Presentation: the video of this talk is not available.