Electroweak chiral Lagrangian with a light Higgs

Abstract

In this talk we discuss the structure of electroweak low-energy effective theories where the Higgs is non-linearly realized, typically in scenarios where the Higgs is a pseudo Nambu-Goldstone boson of some beyond Standard Model symmetry. The organization of the perturbative counting and the relevance of the various next-to-leading order contributions is studied. We discuss some new results on the structure of the one-loop ultraviolet divergences and the contribution from tree-level heavy resonance exchanges to the low-energy effective theory, which are applied to a couple of explicit examples in order to show how, in the non-linear effective theory -the electroweak chiral Lagrangian with a light Higgs (ECLh)-, one-loop corrections can be as important as the contribution from higher dimension operators.