YUKAWA UNIFICATION

We present a complete one-loop calculation of the top- and bottom-quark and the tau lepton masses in two classes of unified supersymmetric models with minimal (SSM) and non-minimal (EVSSM) matter content. In the EVSSM heavy extra vector-like fields are added with masses chosen to hit the string unification scale of O(10(18) GeV), while keeping the successful value of sin(2)theta(w) almost-equal-to 0.233. We examine both SU(5)-type (lambda(b) = lambda(tau)) and SO(10)-type (lambda(tau) = lambda(b) = lambda(tau)) Yukawa coupling relations for both models. Our results show that in both models the SU(5)-type Yukawa relation predicts values of m(b) in terms of tan-beta, m(t), and alpha(3), which include the range m(b) = 4.2-5.0 GeV. The SO(10)-type Yukawa relation predicts m(t) and tan-beta in terms of alpha(3) and m(b), with m(t) almost-equal-to 90-160 GeV (SSM) and m(t) almost-equal-to 140-170 GeV (EVSSM) for alpha(3) = 0.113 +/- 0.004 and m(b) = 4.2-5.0 GeV. We also show that most of the SU(5)-type and some of the SO(10)-type allowed values of m(t) and tan-beta in the SSM satisfy the constraints from radiative electroweak symmetry breaking.