DIURNAL AND ANNUAL VARIATIONS OF DIRECTIONAL DETECTION RATES OF DARK MATTER

Abstract

Direction sensitive direct detection of Weakly Interacting Massive Particles\n(WIMPs) as dark matter would provide an unambiguous non-gravitational signature\nof dark matter (DM). The diurnal variation of DM signal due to earth's rotation\naround its own axis can be a significant signature for galactic WIMPs. Because\nof particular orientation of earth's axis of rotation with respect to WIMP wind\ndirection, the apparent direction of WIMP wind as observed at a detector can\nalter widely over a day. In this work we calculate the directional detection\nrates with their daily and yearly modulations in earth-bound dark matter\nexperiments considering detailed features of the geometry and dynamics of the\nearth-sun system along with the solar motion in galactic frame. A separate halo\nmodel namely the dark disc model other than the usual standard halo model for\ndark matter halo is also considered and the results for two models are\ncompared. We demonstrate the results for two types of gas detectors namely\nDRIFT (target material CS2) and NEWAGE (target material CF4) that use Time\nProjection Chamber techniques for measuring directionality of the recoil\nnucleus. The WIMP mass and recoil energy dependence of the daily variation of\nevent rates are computed for specific detector and the sensitive ranges of mass\nand recoil energies for the considered detector are probed.\n