Refined Analysis of the Electroweak Precision Data

We refine our recent analysis of the electroweak precision data at the \PZO\ pole by including the hadronic decay modes of the \PZO. Within the framework of an effective Lagrangian we parametrize $SU(2)$ violation by the additional process-specific parameters $\De y_\nu$, $\De\yh$, and $\De\yb$ (for the $\PZO\nu\bar\nu$, $\PZO\Pq\bar\Pq$, and $\PZO\Pb\bar\Pb$ vertices) together with the previously introduced parameters $\De x$, $\De y$, and $\eps$. We find that a six-parameter analysis of the experimental data is indeed feasible, and it is carried out in addition to a four-parameter fit for $\De x$, $\De y$, $\eps$, and $\De\yb$ only. We reemphasize that the experimental data have become sensitive to the (combined) magnitude of the vertex corrections at the $\PWp\Pl\bar\nu$ ($\PWm\nu\bar\Pl$) and $\PZO\Pl\bar\Pl$ vertices, $\De y$, which is insensitive to the notion of the Higgs mechanism but dependent on the non-Abelian, trilinear vector-boson coupling. Full explicit analytical results for the standard one-loop predictions for the above-mentioned parameters are given, and the leading two-loop top-quark effects are included. The analytic formluae for the analysis of the experimental data in terms of the parameters $\De x$, $\De y$ etc.\ are presented in order to encourage experimentalists to persue such an analysis by themselves with future data.