Violations of universality in a vectorlike extension of the standard model

Abstract

Violations of universality of couplings in a vectorlike extension of the standard model with three heavy mirror fermion families are considered. The recently observed discrepancies between experiments and the standard model in the hadronic branching fractions $R_b$ and $R_c$ of the Z-boson are explained by the mixing of fermions with their mirror fermion partners.

Comments: latex2e, 11 pages