Heavy top quark from Fritzsch mass matrices

It is shown, contrary to common belief, that the Fritzsch Ansatz for the quark mass matrices admits a heavy top quark. With the Ansatz prescribed at the supersymmetric grand unified theory (GUT) scale, one finds that the top quark may be as heavy as 145 GeV, provided that $tan\beta$ (the ratio of the vacuum expectation values of the two Higgs doublets) ≫1. Within a nonsupersymmetric GUT framework with two (one) light Higgs doublets, the corresponding approximate upper bound on the top mass is 120 (90) GeV. Our results are based on a general one-loop renormalization group analysis of the quark masses and mixing angles and are readily applied to alternative mass matrix Ansätze.