Thoughts on CP Violation

The necessary complex structures needed for CP violation are not easy to generate and, indeed, CP can be a symmetry in higher dimensional theories. In 4-dimensions CP violation argues for the existence of a scalar sector and, in its simplest manifestation, leads to the CKM model. Further CP violating phases, from an extended scalar sector, are constrained by the requirement of having no FCNC. Although new CP violating phases are expected in SUSY extensions of the SM, the good agreement of data with the CKM model only provides bounds on these phases. Baryogenesis via leptogenesis requires the presence of CP violating phases in the neutrino sector. However, the CP phases likely to be eventually meausured experimentally are not necessarily directly connected to the ones which drive the leptogenesis.