We discuss a recent analysis of $t\bar{ t}$ threshold effects and its implications for the determination of electroweak parameters. We show that the new formulation, when applied to the $\rho$ parameter for $m_t\approx158$~GeV, gives a result of similar magnitude to those previously obtained. In fact, it is quite close to our ``resonance'' calculation. We also present a simple estimate of the size of the threshold effects based on an elementary Bohr-atom model of $t\bar{ t}$ resonances.
Categories: hep-ph