Light scalars within the $\mathcal{CP}$-conserving Aligned-two-Higgs-doublet model

TL;DR

This paper explores the existence of lighter neutral and charged scalars within the CP-conserving Aligned-two-Higgs-doublet model, using Bayesian global fits to current experimental constraints to identify viable parameter regions.

Contribution

It performs comprehensive Bayesian global fits of seven light-scalar scenarios in the A2HDM, incorporating diverse experimental constraints to identify viable parameter spaces.

Findings

Seven scenarios have sizeable compatible parameter regions.

Current data do not exclude the existence of lighter scalars.

Implications of (g-2)_μ are discussed but not included in the fits.

Abstract

In this article we study the possibility that neutral and charged scalars lighter than the 125 GeV Higgs boson might exist within the framework of the $\mathcal{CP}$-conserving Aligned-two-Higgs-doublet model. Depending on which new scalar (scalars) is (are) light, seven different scenarios may be considered. Using the open-source code HEPfit, which relies on Bayesian statistics, we perform global fits for all seven light-mass scenarios. The constraints arising from vacuum stability, perturbativity, electroweak precision observables, flavour observables, Higgs signal strengths, and direct-detection results at the LEP and the LHC are taken into account. Reinterpreted data from slepton searches are considered too. It turns out that the seven scenarios contain sizeable regions of their parameter space compatible with all current data. Although not included in the global fits, the possible implications of $(g-2)_\mu$ are also addressed.