Resumen de Tests of the Electroweak model in the presence of two Higgs doublets
Despite the successful description of the observed phenomena given by the SM, it leaves many questions unanswered, a big part of them related with the flavour structure itself. The gauge and scalar sectors have 4 free parameters, \alpha_{em}, M_Z, G_F, which are very well determined, and the mass of the Higgs, M_h. Anyway, a model with only 4 degrees of freedom permits to make rather good predictions. However, the fermionic flavour sector introduces 13 more, with 9 fermion masses, 3 mixings and 1 phase. And moreover, if one takes into account that neutrinos are actually massive, 3 more masses need to be added, plus the corresponding mixing matrix for the lepton sector (other 4 parameters, plus 2 new phases if neutrinos are Majorana particles). The existence of all these degrees of freedom comes from the unknown Yukawa couplings, the origin and the structure of which conform an unresolved flavour puzzle. The scalar sector plays an important role in its structure, since the generation of masses is completely related with the electroweak SSB, the most obscure part of the SM Lagrangian. A CP violation mechanism is incorporated by the SM through a single phase in the V matrix. Although it explains (by now) all the observed CP violating phenomena in the laboratory, this mechanism is not enough to describe the matter-antimatter asymmetry of the Universe. Therefore, a fundamental explanation of the origin of CP violation is still absent. Neutrino oscillations are the first phenomenon towards the existence of new flavour physics; in this sense, lepton flavour violation opens a window to a new flavour dynamics lacking in the SM.
