  The search for weakly-interacting massive particle (WIMP) dark matter is
multi-pronged. Ultimately, the WIMP-dark-matter picture will only be confirmed
if different classes of experiments see consistent signals and infer the same
WIMP properties. In this work, we review the ideas, methods, and status of
direct-detection searches. We focus in particular on extracting WIMP physics
(WIMP interactions and phase-space distribution) from direct-detection data in
the early discovery days when multiple experiments see of order dozens to
hundreds of events. To demonstrate the essential complementarity of different
direct-detection experiments in this context, we create mock data intended to
represent the data from the near-future Generation 2 experiments. We consider
both conventional supersymmetry-inspired benchmark points (with
spin-independent and -dependent elastic cross sections just below current
limits), as well as benchmark points for other classes of models (inelastic and
effective-operator paradigms). We also investigate the effect on parameter
estimation of loosening or dropping the assumptions about the local WIMP
phase-space distribution. We arrive at two main conclusions. Firstly, teasing
out WIMP physics with experiments depends critically on having a wide set of
detector target materials, spanning a large range of target nuclear masses and
spin-dependent sensitivity. It is also highly desirable to obtain data from
low-threshold experiments. Secondly, a general reconstruction of the local WIMP
velocity distribution, which will only be achieved if there are multiple
experiments using different target materials, is critical to obtaining a robust
and unbiased estimate of the WIMP mass.
