Model-independent precision constraints on dimension-6 operators

TL;DR

This work develops a model-independent, basis-agnostic EFT framework to constrain dimension-6 operators using electroweak precision data and gauge-boson pair production. By organizing operator effects into oblique corrections, vertex corrections, and triple gauge couplings, the authors identify eight independent combinations constrained by Z/W pole observables and three by WW production, enabling straightforward transfer to any operator basis or UV scenario with heavy states. A global pole fit yields tight constraints on leptonic couplings ($\mathcal{O}(10^{-3})$) and smaller but meaningful bounds on quark couplings, while LEP-2 WW data constrain anomalous TGCs with notable blind directions that are lifted when quadratic terms are included. The framework links precision EW tests to Higgs phenomenology and provides practical, basis-independent constraints that can guide model-building and future collider analyses. It also outlines avenues for extending the analysis to flavor structures beyond flavor universality and to include 4-fermion operators.

Abstract

We discuss electroweak precision constraints on dimension-6 operators in the effective theory beyond the standard model. We identify the combinations of these operators that are constrained by the pole observables (the W and Z masses and on-shell decays) and by the W boson pair production. To this end, we define a set of effective couplings of W and Z bosons to fermions and to itself, which capture the effects of new physics corrections. This formalism clarifies which operators are constrained by which observable, independently of the adopted basis of operators. We obtain numerical constraints on the coefficients of dimension-6 operator in a form that can be easily adapted to any particular basis of operators, or any particular model with new heavy particles.