Universality of Quark-Lepton Mass Matrix

Abstract

The recently observed lepton mixing angle $\theta_{13}$ of the MNS mixing matrix is well incorporated in a universal mixing hypothesis between quark and lepton sectors. This hypothesis asserts that, in the charged lepton diagonal base, all other mass matrices for up- and down-type quarks and light neutrinos are diagonalized by the same unitary matrix except for the phase elements. It is expressed as $V_{CKM}= U_{MNS}(\delta^\prime)^\dagger P U_{MNS}(\delta)$ for quark mixing matrix $V_{CKM}$ and lepton mixing matrix $U_{MNS}(\delta)$ in the phenomenological level. Here $P$ is a diagonal phase mass matrix. $\delta^\prime$ is a slightly different phase parameter from the Dirac CP violating phase $\delta=1.1\pi$ (best fit) in the MNS lepton mixing matrix.