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 tbar{t}gamma cross section together with measurements of the bar{B}rightarrow X_sgamma 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.

Highlights

  • The top quark plays a special role in Standard Model Effective Field Theory (SMEFT) analyses and a large number of precision measurements regarding topquark physics have been performed at the Large Hadron Collider (LHC)

  • 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)

  • The top quark plays a special role in SMEFT analyses and a large number of precision measurements regarding topquark physics have been performed at the LHC

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Summary

Introduction

As the top quark is the only fermion with an O(1) Yukawa coupling, it is of special interest in BSM scenarios explaining the origin of electroweak symmetry breaking (EWSB) For these reasons, numerous SMEFT analyses in the top-quark sector have been performed during the recent past, for example [4,5,6,7,8,9,10,11,12,13,14,15,16,17,18]. We consider ttγ cross sections and the B → Xsγ branching fraction to perform a first consistent fit of SMEFT Wilson coefficients using a combination of topquark and B physics observables that have a common set.

Effective field theories at different scales
Effective Lagrangian for ttγ production
Matching at one-loop level
RGE evolution in SMEFT
Matching SMEFT onto WET
RGE evolution in WET
Measurements of the ttγ cross section
Modeling observables
Constraining Wilson coefficients
B physics only
Top physics only
Combined analysis
Findings
Conclusions

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