New-physics signals of a model with a vector-singlet up-type quark

TL;DR

This paper investigates a model extending the standard model with a vector-singlet up-type quark, analyzing flavor-physics data to constrain new physics signals and potential observable effects in top quark decays.

Contribution

It provides the first comprehensive fit of the full CKM matrix in the VuQ model, constraining new physics contributions and predicting possible enhancements in rare top decays.

Findings

No significant new physics signals detected in CKM matrix

VuQ contributions to flavor-changing processes are very small

Potential enhancements in t -> u Z and t -> c Z decays are below current detection limits

Abstract

The VuQ model involves the addition of a vector isosinglet up-type quark to the standard model. In this model the full CKM quark mixing matrix is 4 X 3. Using present flavor-physics data, we perform a fit to this full CKM matrix, looking for signals of new physics (NP). We find that the VuQ model is very strongly constrained. There are no hints of NP in the CKM matrix, and any VuQ contributions to loop-level flavor-changing b -> s, b -> d and s -> d transitions are very small. There can be significant enhancements of the branching ratios of the flavor-changing decays t -> u Z and t -> c Z, but these are still below present detection levels.