Family unification in SU(6)L x U(1)Y

Electroweak and horizontal interactions are unified with the group SU(6)LxU(1)Y for three generations. The horizontal gauge group suggested from low energy phenomenology is SU(2)H. This model does not contain exotic quarks, but exotix leptons are needed in order to make it anomaly-free. The breaking of the symmetry gives, in a natrual way, heavy masses for exotic leptons and a BCS mass matrix for the up quarks, which implies that at tree level only the top quark gets a mass of order MW. The see-saw mechanism generates tiny masses for the three known neutrinos. The remaining of the known fermion masses are light, because they can be generated only as radiative corrections. (orig.)