Quark-Lepton Complementarity; a Review

Abstract

It has been recognized recently that there is a remarkable empirical relation between lepton and quark mixing angles, theta_{12} + theta_C \approx pi/4. If not accidental, it should testify for yet uncovered new relationship between the fundamental twin particles in nature which only differ in their ability to feel color. The nontrivial structure which is presumed to exist behind the empirical relation is named as ``quark-lepton complementarity''. In this talk, I review the idea at the kind request of the organizer. Starting from pedagogical discussions of bimaximal mixing, which likely to be involved in the whole picture, I try to give a flavor of the new field which is still in rapid development. Toward the more balanced knowledges of flavor mixing in lepton and quark sectors, I describe a promising way for precision measurement of theta_{12} which utilizes solar and reactor neutrinos.