A realistic assessment of the CTA sensitivity to dark matter
  annihilation
  We estimate the sensitivity of the upcoming CTA gamma-ray telescope to DM
annihilation at the Galactic centre, improving on previous analyses in a number
of significant ways. First, we perform a detailed analyses of all backgrounds,
including diffuse astrophysical emission for the first time in a study of this
type. Second, we present a statistical framework for including systematic
errors and estimate the consequent degradation in sensitivity. These errors may
come from e.g. event reconstruction, Monte Carlo determination of the effective
area or uncertainty in atmospheric conditions. Third, we show that performing
the analysis on a set of suitably optimised regions of interest makes it
possible to partially compensate for the degradation in sensitivity caused by
systematics and diffuse emission. To probe dark matter with the canonical
thermal annihilation cross-section, CTA systematics like non-uniform variations
in acceptance over a single field of view must be kept below the 0.3% level,
unless the dark matter density rises more steeply in the centre of the Galaxy
than predicted by a typical Navarro-Frenk-White or Einasto profile. For a
contracted $r^{-1.3}$ profile, and systematics at the 1% level, CTA can probe
annihilation to $b\bar{b}$ at the canonical thermal level for dark matter
masses between 100 GeV and 10 TeV.
