Radiatively Generated Quarks and Lepton Masses in Extended Gauge Theories

The hierarchical structure of fermion masses and mixings is a major unsolved problem in the Standard model. Fermion masses as radiative corrections emerge as one of the reliable explanations for this problem. We propose a framework based on a class of abelian gauge symmetries in which the masses of only the third generation quarks and leptons arise at the tree level, and the lighter generations masses are induced radiatively with new gauge bosons in the loops. We have shown that this class of abelian symmetries are flavour non-universal in nature. We construct an explicit renormalizable model based on two U(1)s which reproduces the observed fermion mass spectrum of the Standard Model, and discuss some phenomenological aspects of the flavourful new physics.