## CP Violation in the Leptonic Sector

Who: Gustavo Castelo-Branco (Lisbon, IST)
When: Monday, March 9, 2015 at 14:15
Where: The CP³ meeting room

We review CP violation in the Standard Model, with emphasis on the leptonic sector. A method to study CP violation is described, including the derivation of weak-basis invariants relevant to both Dirac-type and Majorana-type CP violation. Furthermore, we propose that the observed large leptonic mixing may just reflect a quasi-degeneracy of three Majorana neutrinos. The limit of exact degeneracy of Majorana neutrinos is not trivial, as leptonic mixing and even CP violation may occur. We conjecture that the smallness of |U13|, when compared to the other elements of UPMNS, may be related to the fact that, in the limit of exact mass degeneracy, the leptonic mixing matrix necessarily has a vanishing element. We show that the lifting of the mass degeneracy can lead to the measured value of |U13| while at the same time accommodating the observed solar and atmospheric mixing angles.

#### Media

Slides from the talk