A few words about Resonances in the Electroweak Effective Lagrangian

TL;DR

This paper demonstrates that strongly coupled electroweak models with a light Higgs and vector resonances are compatible with experimental constraints, using an effective Lagrangian and one-loop calculations of oblique parameters.

Contribution

It provides a novel analysis showing the viability of strongly-coupled electroweak models with resonances, constrained by short-distance and dispersive methods.

Findings

Strongly coupled models are compatible with S and T constraints.

Resonance parameters can be constrained using one-loop calculations.

Low energy constants can be estimated from resonance parameters.

Abstract

Contrary to a widely spread believe, we have demonstrated that strongly coupled electroweak models including both a light Higgs-like boson and massive spin-1 resonances are not in conflict with experimental constraints on the oblique S and T parameters. We use an effective Lagrangian implementing the chiral symmetry breaking SU(2)_L x SU(2)_R -> SU(2)_{L+R} that contains the Standard Model gauge bosons coupled to the electroweak Goldstones, one Higgs-like scalar state h with mass m_h=126 GeV and the lightest vector and axial-vector resonance multiplets V and A. We have considered the one-loop calculation of S and T in order to study the viability of these strongly-coupled scenarios, being short-distance constraints and dispersive relations the main ingredients of the calculation. Once we have constrained the resonance parameters, we do a first approach to the determination of the low energy constants of the electroweak effective theory at low energies (without resonances). We show this determination in the case of the purely Higgsless bosonic Lagrangian.