Finkbeiner, DouglasWeiner, Neal2017-07-182007Finkbeiner, Douglas P., and Neal Weiner. 2007. “Exciting Dark Matter and the INTEGRAL/SPI 511 keV Signal.” Physical Review D 76 (8) (October 22). doi:10.1103/physrevd.76.083519.1550-7998http://nrs.harvard.edu/urn-3:HUL.InstRepos:33461888We propose a WIMP candidate with an ``excited state'' 1-2 MeV above the ground state, which may be collisionally excited and de-excites 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 INTEGRAL/SPI in the inner Milky Way. Only a small fraction of the WIMPs 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 ~3x10^42 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.en-USJournal Article2017-05-1720072017-07-1810.1103/physrevd.76.083519