Xing, ZZ (reprint author), Chinese Acad Sci, Inst High Energy Phys, Beijing 100049, Peoples R China.
Article; Proceedings Paper
I argue that the observed flavor structures of leptons and quarks might imply the existence of certain flavor symmetries. The latter should be a good starting point to build realistic models towards deeper understanding of the fermion mass spectra and flavor mixing patterns. The mu-tau permutation symmetry serves for such an example to interpret the almost maximal atmospheric neutrino mixing angle (theta(23) similar to 45 degrees) and the strongly suppressed CHOOZ neutrino mixing angle (theta(13) < 10 degrees). In this talk I like to highlight a new kind of flavor symmetry, the Friedberg-Lee symmetry, for the effective Majorana neutrino mass operator. Luo and I have shown that this symmetry can be broken in an oblique way, such that the lightest neutrino remains massless but an experimentally-favored neutrino mixing pattern is achievable. We get a novel prediction for 013 in the CP-conserving case: sin theta(13) = tan theta(12)vertical bar(1 - tan theta(23))/(1 + tan theta(23))vertical bar. Our scenario can simply be generalized to accommodate CP violation and be combined with the seesaw mechanism. Finally I stress the importance of probing possible effects of mu-tau symmetry breaking either in terrestrial neutrino oscillation experiments or with ultrahigh-energy cosmic neutrino telescopes.