Underlying SU(3) Symmetry of the Standard Model of Electroweak Interactions

The Standard Model for electroweak interactions derives four vector gauge boson from an SU(2)xU(1) symmetry. A doublet of complex scalar (Higgs) bosons is added to generate masses by spontaneous symmetry breaking. Both, the four vector bosons and four scalar bosons corresponding to the Higgs bosons of the Standard Model are shown to emerge as gauge bosons from an underlying SU(3) symmetry of electroweak lepton interactions. For the known leptons, the latter symmetry implies purely axial coupling of the Z boson to charged leptons, if the photon is required to have purely vector coupling. The corresponding Weinberg angle is determined by sin{\theta} = 1/2. The same SU(3) symmetry holds for quarks as well, if the observed fractional electric quark charges are averages of integer charges, according to the Han-Nambu scheme.