Phenomenology of Dark Matter annihilation into a long-lived intermediate
  state
  We propose a scenario where Dark Matter (DM) annihilates into an intermediate
state which travels a distance $\lambda \equiv v/\Gamma$ on the order of
galactic scales and then decays to Standard Model (SM) particles. The long
lifetime disperses the production zone of the SM particles away from the
galactic center and hence, relaxes constraints from gamma ray observations on
canonical annihilation scenarios. We utilize this set up to explain the
electron and positron excesses observed recently by PAMELA, ATIC, and FERMI.
While an explanation in terms of usual DM annihilations seems to conflict with
gamma ray observations, we show that within the proposed scenario, the
PAMELA/ATIC/FERMI results are consistent with the gamma ray data. The
distinction from decay scenarios is discsussed and we comment on the prospects
for DM production at LHC. The typical decay length $\lambda \gtrsim 10$ kpc of
the intermediate state can have its origin from a dimension six operator
suppressed by a scale $\Lambda \sim 10^{13}$ GeV, which is roughly the seesaw
scale for neutrino masses.
