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Simple Non-Abelian Finite Flavor Groups and Fermion Masses

The use of nonabelian discrete groups G as family symmetries is discussed in detail. Out of all such groups up to order g = 31, the most appealing candidates are two subgroups of SU(2): the dicyclic [double dihedral] group G = $Q_6 ={ }^{(d)}D_3$ ( g = 12 ) and the double tetrahedral group $^{(d)}T = Q_4\tilde{\times}Z_3$ ( g = 24 ). Both can allow a hierarchy $t > b, τ> c > s, μ> u, d, e$. The top quark is uniquely allowed to have a G symmetric mass. Sequential breaking of G and radiative corrections give the smaller masses. Anomaly freedom for gauging $G \subset SU(2)$ is a strong constraint in assignment of fermions to representations of G.