Treating Top Differently from Charm and Up

Abstract

It now appears phenomenologically that the third family may be essentially different from the first two. Particularly the high value of the top quark mass suggests a special role. In the standard model all three families are treated similarly [becoming exactly the same at asymptotically high energies] so I need to extend the model to accommodate the goal of a really different third family. In this article I describe not one but two such viable extensions, quite different one from another. The first is the 331 model which predicts dileptonic gauge bosons. In the second, using as a flavor symmetry a finite nonabelian dicyclic $Q_{2N}$ group, I show how to derive quark mass matrices with two arrangements of symmetric texture zeros which are phenomenologically viable. Three other such acceptable textures in the recent literature are unattainable in this approach and hence disfavored. I assume massive vector-like fermions and Higgs singlets transforming as judiciously-chosen $Q_{2N}$ doublets and use the tree-level mass generation mechanism of Froggatt and Nielsen.