A Tale of Tails: Dark Matter Interpretations of the Fermi GeV Excess in
  Light of Background Model Systematics
  Several groups have identified an extended excess of gamma rays over the
modeled foreground and background emissions towards the Galactic center (GC)
based on observations with the Fermi Large Area Telescope. This excess emission
is compatible in morphology and spectrum with a telltale sign from dark matter
(DM) annihilation. Here, we present a critical reassessment of DM
interpretations of the GC signal in light of the foreground and background
uncertainties that some of us recently outlaid in Calore et al. 2014. We find
that a much larger number of DM models fits the gamma-ray data than previously
noted. In particular: (1) In the case of DM annihilation into $\bar{b}b$, we
find that even large DM masses up to $m_\chi \simeq$ 74 GeV are allowed with a
$p$-value $> 0.05$. (2) Surprisingly, annihilation into non-relativistic hh
gives a good fit to the data. (3) The inverse Compton emission from
$\mu^+\mu^-$ with $m_\chi\sim$ 60-70 GeV can also account for the excess at
higher latitudes, $|b|>2^\circ$, both in its spectrum and morphology. We also
present novel constraints on a large number of mixed annihilation channels,
including cascade annihilation involving hidden sector mediators. Finally, we
show that the current limits from dwarf spheroidal observations are not in
tension with a DM interpretation when uncertainties on the DM halo profile are
accounted for.
