Cornering the Two Higgs Doublet Model Type II

TL;DR

This study thoroughly explores the parameter space of the Two Higgs Doublet Model Type II, combining experimental data and theoretical constraints, and finds it fits the data slightly better than the Standard Model, with implications for electroweak baryogenesis.

Contribution

It provides the first comprehensive bounds on 2HDM-II parameters using combined flavour, collider, and electroweak data, and assesses its viability for electroweak baryogenesis.

Findings

Best fit heavy Higgs masses around 2 TeV

Wrong-sign limit is strongly disfavoured

Parameter space discourages strong first order phase transition

Abstract

We perform a comprehensive study of the allowed parameter space of the Two Higgs Doublet Model of Type II (2HDM-II). Using the theoretical framework flavio we combine the most recent flavour, collider and electroweak precision observables with theoretical constraints to obtain bounds on the mass spectrum of the theory. In particular we find that the 2HDM-II fits the data slightly better than the Standard Model (SM) with best fit values of the heavy Higgs masses around 2 TeV and a value of $\tan \beta \approx 4$. Moreover, we conclude that the wrong-sign limit is disfavoured by Higgs signal strengths and excluded by the global fit by more than five standard deviations and potential deviations from the alignment limit can only be tiny. Finally we test the consequences of our study on electroweak baryogenesis via the program package BSMPT and we find that the allowed parameter space strongly discourages a strong first order phase transition within the 2HDM-II.