Dark Matter Direct Search Rates in Simulations of the Milky Way and
  Sagittarius Stream
  We analyze self-consistent N-body simulations of the Milky Way disk and the
ongoing disruption of the Sagittarius dwarf satellite to study the effect of
Sagittarius tidal debris on dark matter detection experiments. In agreement
with significant previous work, we reiterate that the standard halo model is
insufficient to describe the non-Maxwellian velocity distribution of the Milky
Way halo in our equilibrium halo-only and halo/galaxy models, and offer
suggestions for correcting for this discrepancy. More importantly, we emphasize
that the dark matter component of the leading tidal arm of the Sagittarius
dwarf is significantly more extended than the stellar component of the arm,
since the dark matter and stellar streams are not necessarily coaxial and may
be offset by several kpc at the point at which they impact the Galactic disk.
This suggests that the dark matter component of the Sagittarius debris is
likely to have a non-negligible influence on dark matter detection experiments
even when the stellar debris is centered several kpc from the solar
neighborhood. Relative to models without an infalling Sagittarius dwarf, the
Sagittarius dark matter debris in our models induces an energy-dependent
enhancement of direct search event rates of as much as ~20 - 45%, an
energy-dependent reduction in the amplitude of the annual modulation of the
event rate by as much as a factor of two, a shift in the phase of the annual
modulation by as much as ~20 days, and a shift in the recoil energy at which
the modulation reverses phase. These influences of Sagittarius are of general
interest in the interpretation of dark matter searches, but may be particularly
important in the case of relatively light (m_X < 20 GeV) dark matter because
the Sagittarius stream impacts the solar system at high speed compared to the
primary halo dark matter.
