Constraining the Strength and CP Structure of Dark Production at the LHC: the Associated Top-Pair Channel

TL;DR

This paper investigates how the azimuthal angle difference between leptons in top-quark pair decays can reveal the CP nature of mediators involved in dark matter production at the LHC, providing new constraints on model parameters.

Contribution

It introduces a novel method using dileptonic top decay angles to directly probe the CP properties of dark matter mediators at the LHC.

Findings

Constraints on the strength of dark matter production from LHC data

Sensitivity of azimuthal angle difference to CP-structure

Potential to distinguish scalar vs pseudoscalar mediators

Abstract

We consider the production of dark matter in association with a pair of top quarks, mediated by a scalar or pseudoscalar particle in a generic Simplified Model. We demonstrate that the difference of azimuthal angle between the two leptons $\Delta \phi_{ll}$, in the dileptonic top decay mode, can directly probe the CP-properties of the mediator. We estimate the constraints to strength and CP-structure of dark matter production for these well-motivated Simplified Models from the LHC Run II.