b -> s Decays in a model with Z-mediated flavor changing neutral current

TL;DR

This paper investigates Z-mediated flavor changing neutral currents in a model with an added vector-like down-type quark, fitting flavor physics data to constrain the new physics coupling and exploring potential signals in Bs decay observables.

Contribution

It provides the first detailed fit of the Zbs coupling in this model, constraining its magnitude and discussing implications for new physics signals.

Findings

The Zbs coupling is constrained to |U_{sb}| <= 3.40 x 10^{-4} at 3 sigma.

The model allows for possible new physics signals in semileptonic CP asymmetry in Bs decays.

The fit indicates the new physics coupling is small but potentially observable.

Abstract

In the scenario with Z mediated flavor changing neutral current occurring at the tree level due to the addition of a vector-like isosinglet down-type quark d' to the SM particle spectrum, we perform a chi square fit using the flavor physics data and obtain the best fit value along with errors of the tree level Zbs coupling, U_{sb}. The fit indicates that the new physics coupling is constrained to be small: we obtain |U_{sb}| <= 3.40 X 10^{-4} at 3 sigma. Still this does allow for the possibility of new physics signals in some of the observables such as semileptonic CP asymmetry in Bs decays.