Coupling Constant and Yukawa Coupling Unifications: Uncertainties and Constraints

Abstract

The status of coupling constant unification (with and without a unification of Yukawa couplings) is discussed. Uncertainties associated with the input coupling constants, $m_b$ and $m_t$, threshold corrections at the low and high scale, and possible nonrenormalizable operators are described and a discrepancy between effective and physical scales is pointed out. Theoretical uncertainties in the predictions of ${\alpha }_s(M_Z)$, $m_b$, and the unification scale, $M_G$, are discussed and estimated. Constraints on the super-partner spectrum are found to be weak if uncertainties associated with the high-scale are included. However, requiring $h_b=h_{\tau }$ at $M_G$ excludes $3<\tan \beta <40$ (for $m_t<200$ GeV).

(talk presented at the SUSY-93 Workshop), 7 pages + 2 figures (figures are available upon request), LaTex, UPR-0571T