Model-independent precision constraints on dimension-6 operators

TL;DR

This paper analyzes how electroweak precision measurements constrain dimension-6 operators in the effective field theory beyond the standard model, providing a basis-independent framework and numerical bounds on operator coefficients.

Contribution

It introduces a basis-independent formalism linking electroweak observables to dimension-6 operators and provides adaptable numerical constraints on their coefficients.

Findings

Identifies operator combinations constrained by pole observables and W pair production.

Defines effective couplings capturing new physics effects.

Provides numerical bounds on operator coefficients adaptable to various models.

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.