The C2HDM revisited

TL;DR

This paper re-analyzes the complex two-Higgs doublet model (C2HDM), providing a new computational tool, reviewing its parameter space under current constraints, and exploring its potential for CP-violation discovery at the LHC.

Contribution

It introduces the C2HDM_HDECAY code, performs a detailed parameter space analysis, and discusses phenomenological implications for CP-violation detection at the LHC.

Findings

Large CP-odd couplings to fermions remain allowed.

Benchmark points for CP-violation scenarios are identified.

Correlations between CP-violation measures and observables are analyzed.

Abstract

The complex two-Higgs doublet model is one of the simplest ways to extend the scalar sector of the Standard Model to include a new source of CP-violation. The model has been used as a benchmark model to search for CP-violation at the LHC and as a possible explanation for the matter-antimatter asymmetry of the Universe. In this work, we re-analyse in full detail the softly broken $\mathbb{Z}_2$ symmetric complex two-Higgs doublet model (C2HDM). We provide the code C2HDM_HDECAY implementing the C2HDM in the well-known HDECAY program which calculates the decay widths including the state-of-the-art higher order QCD corrections and the relevant off-shell decays. Using C2HDM_HDECAY together with the most relevant theoretical and experimental constraints, including electric dipole moments (EDMs), we review the parameter space of the model and discuss its phenomenology. In particular, we find cases where large CP-odd couplings to fermions are still allowed and provide benchmark points for these scenarios. We examine the prospects of discovering CP-violation at the LHC and show how theoretically motivated measures of CP-violation correlate with observables.