Muon Anomalous Magnetic Moment in Two Higgs Doublet Models with Vector-Like Leptons

TL;DR

Incorporating vector-like leptons into Two-Higgs Doublet Models expands the parameter space to explain the muon g-2 anomaly, accommodating heavier pseudoscalars and lower tan beta values while satisfying experimental constraints.

Contribution

This work demonstrates that adding vector-like leptons to 2HDMs significantly broadens the viable parameter space for explaining muon g-2, especially in Type-X and Type-II scenarios.

Findings

Vector-like leptons enable larger pseudoscalar masses (~1 TeV).

Allowed tan beta values can be as low as 10.

Parameter space is constrained by flavor observables in Type-II models.

Abstract

We show that inclusion of a single generation of vector-like leptons in the Two-Higgs Doublet Models significantly enlarges the allowed parameter space consistent with the muon anomalous magnetic moment, as well as with other theoretical and experimental constraints. While previously $(g -2)_\mu$ could only be resolved in Type-X scenario by requiring a light pseudoscalar Higgs boson and large $\tan \beta$, contributions of vector-like leptons via two-loop Barr Zee diagrams broaden the allowed parameter space, allowing $\tan \beta$ as low as 10 and pseudoscalar masses as large as $\cal{O}$(1 TeV) while fulfilling the stringent constraints from precision and flavor observable. Similar results are obtained for Type-II scenarios, but there the parameter space is more restricted by flavor observables.