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

## TL;DR

This paper enhances dark matter searches at the LHC by using angular correlations, specifically the azimuthal angle difference between jets, to improve discrimination of signals in mono-jet plus missing energy events.

## Contribution

It introduces a novel analysis strategy utilizing the dijet azimuthal angle difference to better distinguish dark matter signals from background in mono-jet events at the LHC.

## Key findings

- Shape fit to $ riangle ilde{ ext{phi}}_{j_1 j_2}$ improves sensitivity.
- Constraints are more stringent than standard $E_T^{ ext{miss}}$ analyses.
- Effective in spin-0 $s$-channel dark matter models.

## Abstract

We reemphasise the usefulness of angular correlations in LHC searches for missing transverse energy ($E_T^{\mathrm{miss}}$) 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 $\Delta \phi_{j_1 j_2}$ in $2 j +E_T^{\mathrm{miss}}$ production provides a powerful discriminant in realistic searches. Employing a shape fit to $\Delta \phi_{j_1 j_2}$, 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 $\Delta \phi_{j_1 j_2}$ shape fit turn out to be significantly more stringent than those that derive from standard $E_T^{\mathrm{miss}}$ shape analyses.