The impact of going beyond the Maxwell distribution in direct dark matter detection rates

We consider direct dark matter detection rates and investigate the difference between a standard Maxwell-Boltzmann velocity distribution and a ''realistic'' distribution like the ones extracted from numerical N-body simulations. Sizable differences are observed when such results are compared to the standard Maxwell-Boltzmann distribution. For a light target both the total rate and the annual modulation are reduced by {approx}25%. For a heavy target the total rate is virtually unchanged, whereas the annual modulation is modified by up to 50%, depending on the weakly interacting massive particle mass and detector energy threshold. We also consider the effect of a possible velocity anisotropy, and the effect is found to be largest for a light target. For the realistic velocity distribution the anisotropy may reduce the annual modulation, in contrast to the Maxwell-Boltzmann case.