Discrimination of anisotropy in dark matter velocity distribution with
  directional detectors
  Directional detection of dark matter has sensitivity for both recoil energy
and direction of nuclear recoil. It opens the way to measure local velocity
distribution of dark matter. In this paper, we study possibility to
discriminate isotropic distribution and anisotropic one suggested by a N-body
simulation with directional detector. Numerical simulation is performed for two
cases according to the detectors, one corresponds to angular histogram and the
other is energy-angular distribution of the signals. We reveal that the
anisotropy of velocity distribution can be discriminated at 90% C.L. with
chi-squared test if O($10^4$) signals are obtained.
