  Weakly interacting massive particles (WIMPs) form a promising solution to the
dark matter problem and many experiments are now searching for these particles.
Using effective field theories to describe the interaction of the WIMP with the
Standard Model has proven successful in providing an easy way to compare the
different experimental results. In this work, we show how effective operators
can be formally derived from a UV-complete underlying theory, and we analyse
these operators in different experimental contexts. We put our main focus on
the expected sensitivity of the International Linear Collider (ILC) in
searching for WIMPs by looking at events with single photons in the final
state. Furthermore, we show explicit evaluations of the relic density
measurements from the Wilkinson Microwave Anisotropy Probe and the XENON Dark
Matter Project direct detection measurements to compare to the expected ILC
results. We find that the ILC serves as a unique tool to probe possible WIMP
interactions with the Standard Model for dark matter masses below 10 GeV. This
extends to masses up to 490 GeV in cases where the interaction is
spin-dependent or leptophilic.
