Long-Range Forces in Direct Dark Matter Searches
  We discuss the positive indications of a possible dark matter signal in
direct detection experiments in terms of a mechanism of interaction between the
dark matter particle and the nuclei occurring via the exchange of a light
mediator, resulting in a long-range interaction. We analyze the annual
modulation results observed by the DAMA and CoGeNT experiments and the observed
excess of events of CRESST. In our analysis, we discuss the relevance of
uncertainties related to the velocity distribution of galactic dark matter and
to the channeling effect in NaI. We find that a long-range force is a viable
mechanism, which can provide full agreement between the reconstructed dark
matter properties from the various experimental data sets, especially for
masses of the light mediator in the 10-30 MeV range and a light dark matter
with a mass around 10 GeV. The relevant bounds on the light mediator mass and
scattering cross section are then derived, should the annual modulation effects
be due to this class of long-range forces.
