On the use of the escape speed estimates in setting dark matter direct detection limits

The knowledge of the high velocity tail of the WIMP velocity distribution has a strong impact on the way direct detection (DD) may constrain or discover light WIMPs in the GeV mass range. Recently, there have been important observational efforts to estimate the so-called Galactic escape speed at the position of the Earth, for instance the analysis published in early 2014 by the RAVE Collaboration ' , which is of interest in the perspective of reducing the astrophysical uncertainties in DD. Nevertheless, these new estimates cannot be used blindly as they rely on assumptions in the dark halo modeling, which induce tight correlations between the escape speed and other local astrophysical parameters (e.g. the local circular speed and dark matter density). We make a self-consistent study of the implications of the RAVE results on DD assuming isotropic DM velocity distributions, both Maxwellian and ergodic. Taking as reference the experimental sensitivities currently achieved by LUX, CRESST2, and SuperCDMS, we show that the DD constraints on WIMPs (and associated uncertainties) are slightly stronger (moderate).