On the Interpretation of the Electroweak Precision Data

Abstract

The recent precision electroweak data on ${\Gamma }^l,{\bar{s}}_W^2$ and $M_W/M_Z$ are compared with the tree-level and the dominant-fermion-loop as well as the full one-loop standard-model predictions. While the tree-level predictions are ruled out, the dominant-fermion-loop predictions, defined by using $\alpha (M_Z^2)\cong 1/128.9$ in the tree-level formulae, as well as the full one-loop predictions are consistent with the experimental data. Deviations from the dominant-fermion-loop predictions are quantified in terms of an effective Lagrangian containing three additional parameters which have a simple meaning in terms of $SU(2)$ symmetry violation. The effective Lagrangian yields the standard one-loop predictions for specific values of these parameters, which are determined by $m_t$ and $m_H$.

Preprint BI-TP 93/46 (September 1993), to be published in Phys. Lett. B, LaTeX, 10 pages, (figures are not included)