Exciting dark matter and the INTEGRAL/SPI 511 keV signal

Douglas P. Finkbeiner, Neal Weiner

    Research output: Contribution to journalArticlepeer-review


    We propose a dark matter candidate with an "excited state" 1-2 MeV above the ground state, which may be collisionally excited and deexcites by e+e- pair emission. By converting its kinetic energy into pairs, such a particle could produce a substantial fraction of the 511 keV line observed by the International Gamma-Ray Astrophysics Laboratory/SPI in the inner Milky Way. Only a small fraction of the dark matter candidates have sufficient energy to excite, 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 1% per Hubble time, enough power is available to produce the ∼3×1042 pairs per second observed in the galactic bulge. We specify the parameters of a pseudo-Dirac fermion designed to explain the positron signal, and find that it annihilates chiefly to e+e- and freezes out with the correct relic density. We discuss possible observational consequences of this model.

    Original languageEnglish (US)
    Article number083519
    JournalPhysical Review D - Particles, Fields, Gravitation and Cosmology
    Issue number8
    StatePublished - Oct 22 2007

    ASJC Scopus subject areas

    • Nuclear and High Energy Physics
    • Physics and Astronomy (miscellaneous)


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