Model-independent Analyses of Dark-Matter Particle Interactions
  A model-independent treatment of dark-matter particle elastic scattering has been developed, yielding the most general interaction for WIMP-nucleon low-energy scattering, and the resulting amplitude has been embedded in the nucleus, taking into account the selection rules imposed by parity and time-reversal. One finds that, in contrast to the usual spin-independent/spin-dependent (SI/SD) formulation, the resulting cross section contains six independent nuclear response functions, three of which are associated with possible velocity-dependent interactions. We find that current experiments are four orders of magnitude more sensitive to derivative couplings than is apparent in the standard SI/SD treatment, which necessarily associates such interactions with cross sections proportional to the square of the WIMP velocity relative to the nuclear center of mass. 
Nikhil Anand, A. Liam Fitzpatrick, and W. C. Haxton
nucl-th hep-ex hep-ph nucl-ex