Leptonic CP Violation Phases, Quark-Lepton Similarity and Seesaw Mechanism

Understand

We explore generic features of the leptonic CP violation in the framework of the seesaw type I mechanism with similarity of the Dirac lepton and quarks mass matrices $m_D$.

• For this, we elaborate on the standard parametrization conditions which allow to simultaneously obtain the Dirac and Majorana phases.
• If the only origin of CP violation is the left-handed (LH) transformation which diagonalizes $m_D$ (similar to quarks), the leptonic CP violation is suppressed and the Dirac phase is close to $\pi$ or to $0$ with $\sin \delta_{CP} \approx (\sin \theta_{13}^q /\sin \theta_{13}) \cos \theta_{23} \sin \delta_q \sim \lambda^2 \sin \delta_q$.
• Here $\lambda \sim \theta_C$, is the Cabibbo mixing angle, and $\theta_{13}^q$ and $\theta_{13}$ are the 1-3 mixing angles of quarks and leptons respectively.