Quark-Lepton Flavor Democracy and the Non-Existence of the Fourth Generation

Abstract

In the Standard Model with two Higgs doublets (type II), which has a consistent trend to a flavor gauge theory and its related flavor democracy in the quark and the leptonic sectors (unlike the minimal Standard Model) when the energy of the probes increases, we impose the mixed quark-lepton flavor democracy at high ``transition'' energy and assume the usual see-saw mechanism, and consequently find out that the existence of the fourth generation of fermions in this framework is practically ruled out.