Leptonic CP Violation and Baryon Asymmetry
  The observation of neutrino masses leads to the possibility of leptonic mixing and CP violation. One of the simplest extensions of the Standard Model giving rise to neutrino masses consists of the introduction of one righthanded neutrino field per generation, singlet of SU(2). In the context of the seesaw mechanism this leads to three light and three heavy neutrinos. The charged current interactions couple the charged leptons to both the light and the heavy physical neutrinos and leptonic CP violation may occur at low energies as well as at high energies giving rise to the possibility of leptogenesis. There are special scenarios where it is possible to establish a connection between CP violation at the two different scales, an interesting example is included in this work. Furthermore, we describe how the conjecture that all phenomena of CP violation present in nature could have a common origin can be realized in the framework of a further minimal extension of the Standard Model with CP broken through the phase of the vacuum expectation value of a complex Higgs singlet. 
M. N. Rebelo