Luminous Dark Matter
  We propose a dark matter model in which the signal in direct detection
experiments arises from electromagnetic, not nuclear, energy deposition. This
can provide a novel explanation for DAMA while avoiding many direct detection
constraints. The dark matter state is taken nearly degenerate with another
state. These states are naturally connected by a dipole moment operator, which
can give both the dominant scattering and decay modes between the two states.
The signal at DAMA then arises from dark matter scattering in the Earth into
the excited state and decaying back to the ground state through emission of a
single photon in the detector. This model has unique signatures in direct
detection experiments. The density and chemical composition of the detector is
irrelevant, only the total volume affects the event rate. In addition, the
spectrum is a monoenergetic line, which can fit the DAMA signal well. This
model is readily testable at experiments such as CDMS and XENON100 if they
analyze their low-energy, electronic recoil events.
