On the Validity of Effective Operators for WIMP searches in $t$-channel models

It is now clear that there are sever limitations to the validity of the effective operator description for dark matter interactions at the LHC. We extend recent analyses by investigating the case in which Dirac dark matter couples to standard model quarks via $t$-channel exchange of a scalar mediator. We measure the validity of the effective operator description of this model, at both $\sqrt{s}$ = 8 TeV and 14 TeV. We also point out the general trend that in the regions where the effective operator description is valid, the dark matter relic abundance is typically large