Searching for dark matter in final states with two jets and missing transverse energy

We reemphasise the usefulness of angular correlations in LHC searches for missing transverse energy (E_T^miss) signatures that involve jet (j) pairs with large invariant mass. For the case of mono-jet production via gluon-fusion, we develop a realistic analysis strategy that allows to split the dark matter (DM) signal into distinct one jet-like and two jet-like event samples. By performing state-of-the-art Monte Carlo simulations of both the mono-jet signature and the standard model background, it is shown that the dijet azimuthal angle difference $\Delta {\varphi }_{j_1{j}_2}$ in 2j + E_T^miss production provides a powerful discriminant in realistic searches. Employing a shape fit to $\Delta {\varphi }_{j_1{j}_2}$, we then determine the LHC reach of the mono-jet channel in the context of spin-0 s-channel DM simplified models. The constraints obtained by the proposed $\Delta {\varphi }_{j_1{j}_2}$ shape fit turn out to be significantly more stringent than those that derive from standard E_T^miss shape analyses.