Constraining four-heavy-quark operators with top-quark, Higgs, and electroweak precision data

We establish constraints on the dimension-six four-heavy-quark operators in the Standard Model Effective Field Theory (SMEFT) by synthesising LHC measurements of top-quark and single-Higgs production with electroweak precision observables. We scrutinise the choice of the ${\gamma }_5$ scheme in single-Higgs calculations, demonstrating its non-negligible impact on SMEFT fits.