Global fit of the Aligned Two-Higgs-Doublet Model

TL;DR

This paper performs a comprehensive Bayesian global fit of the aligned two-Higgs-doublet model (ATHDM), integrating theoretical constraints and experimental data to explore its parameter space under specific assumptions.

Contribution

It provides the first global Bayesian analysis of the ATHDM considering stability, perturbativity, and experimental constraints, assuming heavier additional scalars and no new CP violation sources.

Findings

Constraints on the scalar masses and couplings.

Allowed parameter space consistent with current data.

Implications for future collider searches.

Abstract

Though the Standard Model (SM) provides a very elegant description of the interactions among fundamental particles, there are ample evidences suggesting that new physics is needed. In particular, extending the scalar sector has enough motivation from vacuum stability, electroweak phase transition and various other sectors. Among different such extensions, the two-Higgs-doublet model (THDM) is the simplest one that preserves the electroweak $\rho$ parameter. Flavour-changing neutral currents (FCNC) are usually avoided by implementing additional discrete symmetries, but this type of models are subject to severe phenomenological constraints. In the more general framework of the aligned THDM (ATHDM) tree-level FCNCs are avoided by choosing the same flavour structure for the Yukawa couplings of the two scalar doublets, which results in weaker phenomenological constraints. Here, we present a global fit of the ATHDM, using the package HEPfit that performs a bayesian analysis on the parameter-space of this model with the help of stability and perturbativity bounds, experimental data for various flavour and electroweak precision observables, and constraints from Higgs searches at the LHC. This global fit has been performed assuming that all additional scalars are heavier than the SM Higgs and that there are no extra sources of CP violation beyond the CKM phase.