  Arguments coming from Quantum Field Theory are supplemented with a 1-loop
perturbative calculation to settle the non-unitarity of mixing matrices linking
renormalized mass eigenstates to bare flavor states for non-degenerate coupled
fermions. We simultaneously diagonalize the kinetic and mass terms and
counterterms in the renormalized Lagrangian. SU(2)_L gauge invariance
constrains the mixing matrix in charged currents of renormalized mass states,
for example the Cabibbo matrix, to stay unitary. Leaving aside CP violation, we
observe that the mixing angles exhibit, within experimental uncertainty, a very
simple breaking pattern of SU(2)_f horizontal symmetry linked to the algebra of
weak neutral currents, the origin of which presumably lies beyond the Standard
Model. It concerns: on one hand, the three quark mixing angles; on the other
hand, a neutrino-like pattern in which theta_{23} is maximal and tan(2
theta_{12})=2. The Cabibbo angle fulfills the condition tan (2 theta_c)=1/2 and
theta_{12} for neutrinos satisfies accordingly the "quark-lepton
complementarity condition" theta_c + theta_{12}= \pi/4. theta_{13} = +- 5.7
10^{-3} are the only values obtained for the third neutrino mixing angle that
lie within present experimental bounds. Flavor symmetries, their breaking by a
non-degenerate mass spectrum, and their entanglement with the gauge symmetry,
are scrutinized; the special role of flavor rotations as a very mildly
brokensymmetry of the Standard Model is outlined.
