So far LHC has found only a relatively light Higgs boson with mass
mh=126 GeV and no beyond-SM particle has appeared yet below the TeV.
Likewise, there have been no significant deviations in the interaction
couplings with respect to the expected SM values. EW chiral
Lagrangians are found to be, therefore, a natural and systematic
approach for the study of this type of scenarios. However, due to the
tight constraints from LHC data, one needs to go beyond the leading
order approximation in order to disentangle possible new physics. This
is, full one-loop effects must be computed and handled in a systematic
way; tree-level phenomenological estimates are simply not accurate
enough and miss crucial contributions.
More specifically, I will discuss the one-loop calculation of the
photon-photon transition into longitudinal ZZ and W+W-, and related
observables like e.g. the oblique parameter S, at the one-loop level.
The renormalization and running of the relevant chiral couplings are
analyzed and a joined analysis of several observables (photon-photon
transitions, decay rates, oblique parameters and form-factors) is
proposed for the extraction of the corresponding EW Lagrangian parameters.
In the last part of the talk, I will look at the particular predictions
that arise in strongly-coupled models with resonances. Strongly coupled
EW models with massive resonances are found not in conflict with the
experimental S and T as far as the masses of the new vector and
axial-vector resonance lie above the TeV scale and the hWW coupling
remains close to the Standard Model one.
All through the talk we will employ usual QCD tools such as effective
chiral Lagrangians, Weinberg's EFT dimensional power counting and
dispersion relations.