Two-Loop Contributions to the Anomalous Chromomagnetic Dipole Moment of the Top Quark in Two-Higgs-Doublet Models

TL;DR

This paper calculates the two-loop contributions to the anomalous chromomagnetic dipole moment of the top quark within two-Higgs-doublet models, providing analytical results and numerical estimates relevant for high-energy physics.

Contribution

It offers the first analytical two-loop calculations of the top quark's chromomagnetic moment in two-Higgs-doublet models, including off-shell gluon effects.

Findings

Two-loop contributions are about 10^{-4}, smaller than one-loop.

One-loop and two-loop effects interfere destructively.

Overall contributions are around 10^{-3} with positive sign.

Abstract

We present the analytical results for the anomalous chromomagnetic moment of a quark at the one-loop and two-loop levels through model-independent parameterizations, considering the external gluon to be off-shell. Then, we consider different types of two-Higgs doublet models with the momentum transfer of the external gluon, $q^2 = \pm M_Z^2$, and $0$, for the numerical evaluations thereof for the top quark. We find that the contributions in the two-Higgs-doublet models are on the order of $\mathcal{O}(10^{-3})$ at the one-loop level and $\mathcal{O}(10^{-4})$ at the two-loop level, where the one-loop and two-loop contributions interfere destructively, resulting in the overall contributions being on the order of $\mathcal{O}(10^{-3})$ with a positive sign.