Radiatively Generated Fermion Masses In $SU(4)\times SU(2{)}_L\times SU(2{)}_R$

Abstract

We propose a model based on the gauge group $SU(4)\times SU(2{)}_L\times SU(2{)}_R$ where the Dirac masses of all the known fermions are generated as one-loop radiative corrections. We are able to generate realistic quark and lepton masses and mixings without a large hierarchy of Yukawa couplings or extra symmetries. The neutrino masses, which are see-saw suppressed, lie in the mass range favored to solve the solar neutrino problem. The importance of threshold corrections to tree-level mass relations in certain non-supersymmetric GUTs is demonstrated.

Comments: 23 pages, Latex. 3 figures submitted as a uuencoded file. One figure contributing to neutrino mass added changing neutrino mass results. Minor mistakes and typos corrected; numerical example changed to reflect corrections