Dependence of direct detection signals on the WIMP velocity distribution

Abstract

The signals expected in WIMP direct detection experiments depend on the ultra-local dark matter distribution. Observations probe the local density, circular speed and escape speed, while simulations find velocity distributions that deviate significantly from the standard Maxwellian distribution. We calculate the energy, time and direction dependence of the event rate for a range of velocity distributions motivated by recent observations and simulations, and also investigate the uncertainty in the determination of WIMP parameters. The dominant uncertainties are the systematic error in the local circular speed and whether or not the MW has a high density dark disc. In both cases there are substantial changes in the mean differential event rate and the annual modulation signal, and hence exclusion limits and determinations of the WIMP mass. The uncertainty in the shape of the halo velocity distribution is less important, however it leads to a ∼ 5% systematic error in the WIMP mass. The detailed direction dependence of the event rate is sensitive to the velocity distribution. However the numbers of events required to detect anisotropy and confirm the median recoil direction do not change substantially.

Daily modulation due to channeling in direct dark matter crystalline detectors

“…In this paper we take V GalRot either 220 km/s or 280 km/s, as reasonable low and high values (as done in Ref [12]), which correspond to V lab either 228.4 km/s or 288.3 km/s, respectively (see Appendix B for details). Ref.…”

“…We take V GalRot = 220 km/s or 280 km/s [12], V Solar = 18 km/s [26], V EarthRev = 29. We need to computeq · V lab , whereq is given in the crystal reference frame (q = q XX + q YŶ + q ZẐ ).…”

Probing dark matter streams with CoGeNT

“…Direct detection experiments are sensitive to the form of the local dark matter velocity distribution [3][4][5][6], and the results may be significantly modified if a cold stream of dark matter particles exists in the solar neighborhood. Tidal disruption of dwarf satellites is expected to produce * Electronic address: anat@andrew.cmu.edu † Electronic address: savage@fysik.su.se ‡ Electronic address: ktfreese@umich.edu such cold streams.…”

Dark matter in 3D

“…Previous studies in this domain have been carried out in [32][33][34][35][36] assuming specific parameterizations for the functional form of the velocity distribution. One important goal of this article is to investigate the dependence of the dark matter phase space distribution in different coordinates, such as integrals of motion.…”

“…Although the reconstruction of the dark matter distribution function from directional and non-directional detection signals has already been investigated for specific halo types [32][33][34][35][36], no model independent reconstruction study has been performed yet (see, however, halo independent proposals to interpret direct detection signals [59][60][61]). One of the main goals of this paper is to provide a parameterization of the DF that is as generic as possible.…”