A new Wolfenstein-like expansion of lepton flavor mixing towards understanding its fine structure

Taking the tri-bimaximal flavor mixing pattern as a particular basis, we propose a new way to expand the 3×3 unitary Pontecorvo-Maki-Nakagawa-Sakata (PMNS) lepton flavor mixing matrix U in powers of the magnitude of its smallest element ξ≡|Ue3|≃0.149. Such a Wolfenstein-like parametrization of U allows us to easily describe the salient features and fine structures of flavor mixing and CP violation, both in vacuum and in matter.