Reconstructing WIMP Properties in Direct Detection Experiments Including
  Galactic Dark Matter Distribution Uncertainties
  We present a new method for determining Weakly Interacting Massive Particle
(WIMP) properties in future tonne scale direct detection experiments which
accounts for uncertainties in the Milky Way (MW) smooth dark matter
distribution. Using synthetic data on the kinematics of MW halo stars matching
present samples from the Sloan Digital Sky Survey, complemented by local escape
velocity constraints, we demonstrate that the local dark matter density can be
constrained to approximately 20% accuracy. For low mass WIMPs, we find that a
factor of two error in the assumed local dark matter density leads to a
severely biased reconstruction of the WIMP spin-independent cross section that
is incorrect at the 15-sigma level. We show that this bias may be overcome by
marginalizing over parameters that describe the MW potential, and use this
formalism to project the accuracy attainable on WIMP properties in future 1
tonne Xenon detectors. Our method can be readily applied to different detector
technologies and extended to more detailed MW halo models.
