Contact interactions probe effective dark-matter models at the LHC

Effective field theories provide a simple framework for probing possible dark-matter (DM) models by re-parametrising full interactions into a reduced number of operators with smaller dimensionality in parameter space. In many cases these models have four particle vertices, e.g., q (q) over bar chi(chi) over bar, leading to the pair production of dark-matter particles, chi, at a hadron collider from initial state quarks, q. In this analysis we show that for many fundamental DM models with s-channel DM couplings to q (q) over bar pairs, these effective vertices must also produce quark contact interactions (CI) of the form q (q) over barq (q) over bar. The respective effective couplings are related by the common underlying theory which allows one to translate the upper limits from one coupling to the other. We show that at the LHC, the experimental limits on quark contact interactions give stronger translated limits on the DM coupling than the experimental searches for dark-matter pair production. Copyright (c) EPLA, 2013