Mecanismos de Seesaw para neutrinos.

Abstract

The neutrino was initially considered by Wolgang Pauli to explain the beta decay of the neutron, an uncharged particle with a supposedly vanishing mass, which stimulated the study of the theory of weak interactions, formulated by Enrico Fermi. Among all possi- bilities to explain the mass of light neutrinos, the most elegant is through the so-called seesaw mechanism. This can be presented in three different schemes, depending on the particle content that is added to the Standard Model. They all involve heavy particles of right-hand chirality. For types I and III hybridization it is necessary to include a singlet, NR, a fermionic triplet, TR, and a scalar triplet, Σ, all of them with vanishing hypercharge. In this work we study, at the introductory level, the fundamental aspects of the realization of this mechanism and the extension through the type IV minimal seesaw mechanism, where we analyze the possibility of generation of CP violation. The general hybridized case can significantly increase the amount of CP violation generated by the decay of heavy neutrinos. To understand these scheme it is necessary to understand the minimal case, where only fermion singlets are added to Standard Model particle content.