Shielding of a direct detection experiment and implications for the DAMA
  annual modulation signal
  Previous work has argued that, in the framework of plasma dark matter models,
the DAMA annual modulation signal can be consistently explained with electron
recoils. In the specific case of mirror dark matter, that explanation requires
an effective low velocity cutoff, $v_c \gtrsim 30,000$ km/s, for the halo
mirror electron distribution at the detector. We show here that this cutoff can
result from collisional shielding of the detector from the halo wind due to
Earth-bound dark matter. We also show that shielding effects can reconcile the
kinetic mixing parameter value inferred from direct detection experiments with
the value favoured from small scale structure considerations, $\epsilon \approx
2 \times 10^{-10}$.
