Implications of the Fermi-LAT Pass 8 Galactic Center Excess on
  Supersymmetric Dark Matter
  The Fermi Collaboration has recently updated their analysis of gamma rays
from the center of the Galaxy. They reconfirm the presence of an unexplained
emission feature which is most prominent in the region of $1-10$ GeV, known as
the Galactic Center GeV excess (GCE). Although the GCE is now firmly detected,
an interpretation of this emission as a signal of self-annihilating dark matter
(DM) particles is not unambiguously possible due to systematic effects in the
gamma-ray modeling estimated in the Galactic Plane. In this paper we build a
covariance matrix, collecting different systematic uncertainties investigated
in the Fermi Collaboration's paper that affect the GCE spectrum. We show that
models where part of the GCE is due to annihilating DM can still be consistent
with the new data. We also re-evaluate the parameter space regions of the
minimal supersymmetric Standard Model (MSSM) that can contribute dominantly to
the GCE via neutralino DM annihilation. All recent constraints from DM direct
detection experiments such as PICO, LUX, PandaX and Xenon1T, limits on the
annihilation cross section from dwarf spheroidal galaxies and Large Hadron
Collider limits are considered in this analysis. Due to a slight shift in the
energy spectrum of the GC excess with respect to the previous Fermi analysis,
and the recent limits from direct detection experiments, we find a slightly
shifted parameter region of the MSSM compared to our previous analysis that is
consistent with the GCE. Neutralinos with a mass between $85-220$ GeV can
describe the excess via annihilation into a pair of $W$-bosons or top quarks.
Remarkably, there are low fine-tuning models among the regions that we have
found. The complete set of solutions will be probed by upcoming direct
detection experiments and with dedicated searches in the upcoming data of the
Large Hadron Collider.
