One-loop corrections to the $Zb\bar{b}$ vertex in models with scalar doublets and singlets

TL;DR

This paper calculates one-loop corrections to the Zbar{b} vertex in models extending the Standard Model with multiple scalar doublets and singlets, providing general conditions for divergence cancellation and explicit finite expressions.

Contribution

It derives general conditions for divergence cancellation and provides finite expressions for the Zbar{b} vertex corrections in extended scalar models.

Findings

Conditions for divergence cancellation are satisfied in the studied models.

Neutral scalar diagrams significantly impact the vertex corrections.

Explicit finite expressions for the vertex are obtained.

Abstract

We study the one-loop corrections to the $Zb\bar{b}$ vertex in extensions of the Standard Model with arbitrary numbers of scalar doublets, neutral scalar singlets, and charged scalar singlets. Starting with a general parameterization of theories with neutral and singly-charged scalar particles, we derive the conditions that, in a renormalizable model, must be obeyed by the couplings in order for the divergent contributions to cancel. Then, we show that those conditions are indeed obeyed by the models that we are interested in, and we write down the full finite expression for the vertex in those models. We apply our results to some particular cases, highlighting the importance of the diagrams with neutral scalars.