Annihilation vs. Decay: Constraining Dark Matter Properties from a
  Gamma-Ray Detection in Dwarf Galaxies
  Although most proposed dark matter candidates are stable, in order for dark
matter to be present today, the only requirement is that its lifetime is longer
than the age of the Universe, t_U ~ 4 10^17 s. Moreover, the dark matter
particle could be produced via non-thermal processes and have a larger
annihilation cross section from the canonical value for thermal dark matter,
<sigma v> ~ 3 10^{-26} cm3/s. We propose a strategy to distinguish between dark
matter annihilation and/or decay in the case that a clear signal is detected in
future gamma-ray observations of Milky Way dwarf galaxies with gamma-ray
experiments. The discrimination between these cases would not be possible in
the case of the measurement of only the energy spectrum. We show that by
studying the dependence of the intensity and energy spectrum on the angular
distribution of the signal, the origin of the signal could be identified, and
some information about the presence of substructure might be extracted.
