Constraining top-quark couplings combining top-quark and $\boldsymbol{B}$ decay observables

TL;DR

This paper combines top-quark and B physics measurements within SMEFT to improve constraints on top-quark couplings, demonstrating the approach's feasibility and showing no significant deviations from the Standard Model.

Contribution

It introduces a novel combined analysis of top-quark and B physics data within SMEFT, enhancing the sensitivity to new physics in top-quark couplings.

Findings

Combined measurements improve constraints on Wilson coefficients.

No significant deviations from the Standard Model are observed.

The approach demonstrates the benefits of multi-scale observable combination.

Abstract

We present a first, consistent combination of measurements from top-quark and $B$ physics to constrain top-quark properties within the Standard Model Effective Field Theory (SMEFT). We demonstrate the feasibility and benefits of this approach and detail the ingredients required for a proper combination of observables from different energy scales. Specifically, we employ measurements of the $t\bar t\gamma$ cross section together with measurements of the $\bar B\rightarrow X_s\gamma$ branching fraction to test the Standard Model and look for new physics contributions to the couplings of the top quark to the gauge bosons within SMEFT. We perform fits of three Wilson coefficients of dimension-six operators considering only the individual observables as well as their combination to demonstrate how the complementarity between top-quark and $B$ physics observables allows to resolve ambiguities and significantly improves the constraints on the Wilson coefficients. No significant deviation from the Standard Model is found with present data.