On the annual modulation signal in dark matter direct detection
  We derive constraints on the annual modulation signal in Dark Matter (DM)
direct detection experiments in terms of the unmodulated event rate. A general
bound independent of the details of DM distribution follows from the assumption
that the motion of the earth around the sun is the only source of time
variation. The bound is valid for a very general class of particle physics
models and also holds in the presence of an unknown unmodulated background.
More stringent bounds are obtained, if modest assumptions on symmetry
properties of the DM halo are adopted. We illustrate the bounds by applying
them to the annual modulation signals reported by the DAMA and CoGeNT
experiments in the framework of spin-independent elastic scattering. While the
DAMA signal satisfies our bounds, severe restrictions on the DM mass can be set
for CoGeNT.
