Direct detection of self-interacting dark matter
  Self-interacting dark matter offers an interesting alternative to
collisionless dark matter because of its ability to preserve the large-scale
success of the cold dark matter model, while seemingly solving its challenges
on small scales. We present here the first study of the expected dark matter
detection signal taking into account different self-scattering models. We
demonstrate that models with constant and velocity dependent cross sections,
which are consistent with observational constraints, lead to distinct
signatures in the velocity distribution, because non-thermalised features found
in the cold dark matter distribution are thermalised through particle
scattering. Depending on the model, self-interaction can lead to a 10%
reduction of the recoil rates at high energies, corresponding to a minimum
speed that can cause recoil larger than 300 km/s, compared to the cold dark
matter case. At lower energies these differences are smaller than 5% for all
models. The amplitude of the annual modulation signal can increase by up to
25%, and the day of maximum amplitude can shift by about two weeks with respect
to the cold dark matter expectation. Furthermore, the exact day of phase
reversal of the modulation signal can also differ by about a week between the
different models. In general, models with velocity dependent cross sections
peaking at the typical velocities of dwarf galaxies lead only to minor changes
in the detection signals, whereas allowed constant cross section models lead to
significant changes. We conclude that different self-interacting dark matter
scenarios might be distinguished from each other through the details of direct
detection signals. Furthermore, detailed constraints on the intrinsic
properties of dark matter based on null detections, should take into account
the possibility of self-scattering and the resulting effects on the detector
signal.
