H\to\gamma\gamma in the Complex Two Higgs Doublet Model

TL;DR

This paper investigates the complex Two Higgs Doublet Model with CP violation, analyzing its ability to explain the 125 GeV Higgs signals at the LHC, especially the diphoton excess, considering theoretical and experimental constraints.

Contribution

It provides a detailed parameter space analysis of the c2HDM with CP violation, demonstrating its potential to account for LHC Higgs signals and exploring CP-violating effects on observables.

Findings

The c2HDM can explain the LHC diphoton excess within certain parameter regions.

CP-violating phases influence polarization-based CP violation observables.

The model remains consistent with theoretical constraints like positivity, unitarity, and experimental data.

Abstract

We explore the parameter regions in the complex Two Higgs Doublet Model (c2HDM) with explicit CP violation that can describe current LHC hints for one or more Higgs boson signals at 125 GeV. Such a simple extension of the Standard model has three neutral Higgs bosons and a pair charged Higgs and leads to rich CP-violating sources including the CP-even CP-odd mixing of the neutral Higgs bosons. Within this model we present the production of light Higgs boson at the LHC followed by its decay into two photons. Our numerical study takes into account theoretical and experimental constraints on the Higgs potential like positivity, unitarity and perturbativity as well as $\rho$-parameter, $b\to s\gamma$ and $R_b$. These requirement together with the minimum conditions could explain the di-photon excess observed at the LHC. We also discuss the effects of the CP violating phases on the CP violation observable which is the difference between left-circular and right-circular polarization.