Magnetic Inelastic Dark Matter: Directional Signals Without a
  Directional Detector
  The magnetic inelastic dark matter (MiDM) model, in which dark matter
inelastically scatters off nuclei through a magnetic dipole interaction, has
previously been shown to reconcile the DAMA/LIBRA annual modulation signal with
null results from other experiments. In this work, we explore the unique
directional detection signature of MiDM. After the dark matter scatters into
its excited state, it decays with a lifetime of order 1 microsecond and emits a
photon with energy ~100 keV. Both the nuclear recoil and the corresponding
emitted photon can be detected by studying delayed coincidence events. The
recoil track and velocity of the excited state can be reconstructed from the
nuclear interaction vertex and the photon decay vertex. The angular
distribution of the WIMP recoil tracks is sharply peaked and modulates daily.
It is therefore possible to observe the directional modulation of WIMP-nucleon
scattering without a large-volume gaseous directional detection experiment.
Furthermore, current experiments such as XENON100 can immediately measure this
directional modulation and constrain the MiDM parameter space with an exposure
of a few thousand kg day.
