  We study diffuse gamma-ray emission at intermediate Galactic latitudes
measured by the Fermi Large Area Telescope with the aim of searching for a
signal from dark matter annihilation or decay. In the absence of a robust dark
matter signal, we set conservative dark matter limits requiring that the dark
matter signal does not exceed the observed diffuse gamma-ray emission. A second
set of more stringent limits is derived based on modeling the foreground
astrophysical diffuse emission. Uncertainties in the height of the diffusive
cosmic-ray halo, the distribution of the cosmic-ray sources in the Galaxy, the
cosmic-ray electron index of the injection spectrum and the column density of
the interstellar gas are taken into account using a profile likelihood
formalism, while the parameters governing the cosmic-ray propagation have been
derived from fits to local cosmic-ray data. The resulting limits impact the
range of particle masses over which dark matter thermal production in the early
Universe is possible, and challenge the interpretation of the PAMELA/Fermi-LAT
cosmic ray anomalies as annihilation of dark matter.
