Abstract
Recent measurements at the Large Hadron Collider allow for a robust and precise characterisation of the electro-weak interactions of the top quark. We present the results of a global analysis at next-to-leading order precision including LHC, LEP/SLD and Tevatron data in the framework of the Standard Model Effective Field Theory. We include a careful analysis of the impact of correlations among measurements, as well as of the uncertainties in the Effective Field Theory setup itself. We find remarkably robust global fit results, with central values in good agreement with the Standard Model prediction, and 95% probability bounds on Wilson coefficients that range from ±0.35 to ±8 TeV−2. This result represents a considerable improvement over previous studies, thanks to the addition of differential cross-section measurements in associated production processes of top quarks and neutral gauge bosons.
Highlights
We present the results of a global analysis at next-to-leading order precision including Large Hadron Collider (LHC), LEP/SLD and Tevatron data in the framework of the Standard Model Effective Field Theory
We find remarkably robust global fit results, with central values in good agreement with the Standard Model prediction, and 95% probability bounds on Wilson coefficients that range from ±0.35 to ±8 TeV−2
Compared to previous Effective Field Theory (EFT) analyses of the top quark sector [6–10], we extend the set of measurements considerably
Summary
Effects of new physics in the couplings of the top quarks can be described as effective interactions of SM particles at energies below a new physics matching scale Λ. Where the sum runs over a total of ten operators that involve top quarks, as described below, and which can be interpreted in terms of new physics mediators This EFT preserves the local and gauge symmetries of the SM, and operators with odd dimension are omitted since they will violate baryon or lepton number. The electro-weak dipole operators labeled OuW (OdW ) and OuZ (OdZ ) give rise to tensor couplings of the photon and Z boson to the up-type (down-type) quarks and induce an anomalous dipole moment. The Oφ3Q and OuW operators modify the charged-current interactions of the up-type quarks with a W boson and left-handed down-type quark, while. Four-fermion operators with two leptons and two heavy quarks ( QQ) are not included These can be constrained with carefully constructed measurements at the LHC [26] and through loop effects in B-factories [14, 15]. Very strong bounds can be derived at a future lepton collider [6]
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