Form factor dark matter

We present a dynamical alternative to inelastic dark matter as a way of reconciling the modulating signal seen at DAMA with null results at other direct detection experiments. The essential ingredient is a new form factor which introduces momentum dependence in the interaction of dark matter with nuclei. The role of the form factor is to suppress events at low momentum transfer. We find that a form factor approach is most likely not viable in the context of the standard halo model, however it is consistent with halo models suggested by recent Via Lactea simulations. As an example of possible form factors, we present a class of models where the necessary momentum dependence arises from interference of GeV mass gauge bosons coupling the dark matter to nuclei. At energies relevant for direct detection experiments these models contain one or two additional parameters beyond the case of a standard WIMP.