# Simplified dark matter models with two Higgs doublets: I. Pseudoscalar mediators

## TL;DR

This paper introduces a new class of renormalisable dark matter models based on two Higgs doublets with a pseudoscalar mediator, offering rich phenomenology and stronger constraints from various collider and precision measurements.

## Contribution

It develops self-consistent, unitary simplified dark matter models with pseudoscalar mediators, expanding the theoretical framework beyond previous spin-0 models used in Run I analyses.

## Key findings

- Models provide diverse observables for constraints.
- Mono-Z and mono-Higgs channels outperform mono-jet in some regions.
- Multiple experimental bounds effectively test the models.

## Abstract

We study a new class of renormalisable simplified models for dark matter searches at the LHC that are based on two Higgs doublet models with an additional pseudoscalar mediator. In contrast to the spin-0 simplified models employed in analyses of Run I data these models are self-consistent, unitary and bounds from Higgs physics typically pose no constraints. Predictions for various missing transverse energy ($E_{T, \rm miss}$) searches are discussed and the reach of the 13 TeV LHC is explored. It is found that the proposed models provide a rich spectrum of complementary observables that lead to non-trivial constraints. We emphasise in this context the sensitivity of the $t\bar t + E_{T, \rm miss}$, mono-$Z$ and mono-Higgs channels, which yield stronger limits than mono-jet searches in large parts of the parameter space. Constraints from spin-0 resonance searches, electroweak precision measurements and flavour observables are also derived and shown to provide further important handles to constraint and to test the considered dark matter models.