On Diurnal and Annual Variations of Directional Detection Rates of Dark
  Matter
  Direction sensitive direct detection of Weakly Interacting Massive Particles
(WIMPs) as dark matter would provide an unambiguous non-gravitational signature
of dark matter (DM). The diurnal variation of DM signal due to earth's rotation
around its own axis can be a significant signature for galactic WIMPs. Because
of particular orientation of earth's axis of rotation with respect to WIMP wind
direction, the apparent direction of WIMP wind as observed at a detector can
alter widely over a day. In this work we calculate the directional detection
rates with their daily and yearly modulations in earth-bound dark matter
experiments considering detailed features of the geometry and dynamics of the
earth-sun system along with the solar motion in galactic frame. A separate halo
model namely the dark disc model other than the usual standard halo model for
dark matter halo is also considered and the results for two models are
compared. We demonstrate the results for two types of gas detectors namely
DRIFT (target material CS2) and NEWAGE (target material CF4) that use Time
Projection Chamber techniques for measuring directionality of the recoil
nucleus. The WIMP mass and recoil energy dependence of the daily variation of
event rates are computed for specific detector and the sensitive ranges of mass
and recoil energies for the considered detector are probed.
