Charged Higgs Boson Mass Bounds in 2HDM-II: Impact of Vector-Like Quarks

TL;DR

This paper investigates how vector-like quarks affect the mass bounds of charged Higgs bosons in the 2HDM-II, showing that VLQs can relax existing experimental constraints by altering Higgs-quark couplings.

Contribution

It demonstrates that the inclusion of vector-like quarks modifies Higgs couplings, relaxing mass bounds on charged Higgs bosons in 2HDM-II, and analyzes the impact of VLQ mixing on electroweak precision observables.

Findings

VLQs relax $H^\pm$ mass constraints from $B$-physics.

Coupling modifications depend on VLQ representation.

Oblique parameters constrain VLQ mixing angles.

Abstract

We explore the phenomenology of charged Higgs bosons ($H^\pm$) and Vector-Like Quarks (VLQs), specifically the top-like $T$, within the Two Higgs Doublet Model Type-II (2HDM-II). We consider both a singlet VLQ $(T)$ and a doublet $(TB)$ scenario, demonstrating that the presence of VLQs influences the scalar sector, particularly by alleviating the stringent mass constraints on $H^\pm$ imposed by $B$-physics observables such as $B\to X_s\gamma$. This relaxation arises from modifications in the couplings between $H^\pm$ and Standard Model (SM) quarks, with the magnitude of the effect differing between the singlet and doublet cases. We further analyse the constraints from the oblique parameters $S$ and $T$ on VLQ mixing angles.