The Higgs Sector in the Causal Approach

We consider the electro-weak sector of the standard model up to the second order of the perturbation theory (in the causal approach) and derive the most general form of the interaction Lagrangian for an arbitrary number of Higgs fields. The analysis is done in a purely quantum setting. If more than one Higgs field is considered, the values of the Weinberg is not fixed uniquely.