Determining the CP nature of spin-0 mediators in associated production of dark matter and $t \bar t$ pairs

TL;DR

This paper investigates how to determine the CP nature of spin-0 mediators in dark matter production associated with top quark pairs at the LHC, using dilepton final states and sensitivity analysis.

Contribution

It introduces a realistic analysis strategy to distinguish CP properties of mediators in dark matter models at the LHC, including sensitivity estimates and parameter space constraints.

Findings

Upper limits on mediator masses for CP discrimination.

Sensitivity projections for 300 fb^{-1} and 3 ab^{-1} luminosities.

Constraints on simplified dark matter models and extended Higgs sectors.

Abstract

In the framework of spin-0 $s$-channel simplified models, we explore the possibility of assessing the structure of dark matter interactions through the associate production of dark matter and $t\bar{t}$ pairs. To this purpose, final states with two leptons are considered and the kinematic properties of the dilepton system is studied. We develop a realistic analysis strategy and provide a detailed evaluation of the achievable sensitivity for the dark matter signal assuming integrated luminosities of $300 \, {\rm fb}^{-1}$ and $3 \, {\rm ab}^{-1}$ at the 14 TeV LHC. Furthermore, upper limits on the mediator masses for which the two different CP hypotheses can be distinguished are derived. The obtained limits on the signal strengths are finally translated into constraints on the parameter space of two spin-0 simplified models including a scenario with an extended Higgs sector.