189 GeV Data Sample

A summary of the composition of the expected data sample after selection and kinematical fits is shown in table 5.8.

After selection and reconstruction of the OPAL data events at 189 GeV, there were 1246 ${\rm W}^{+}{\rm W}^{-}\rightarrow{\rm q}\bar{\rm q}\ell\bar{\nu}_{\ell}$ events selected. After the kinematic fits were applied this number reduced to 1075 events. Of these 1075 events, 368 were ${\rm q}\bar{\rm q}{\rm e}\bar{\nu}_{\rm e}$, 387 were ${\rm q}\bar{\rm q}\mu\bar{\nu}_{\mu}$ and 320 were ${\rm q}\bar{\rm q}\tau\bar{\nu}_{\tau}$. The angular distributions of these events can be seen in figure 5.9. Also shown on the plots are the expected distributions for the Standard Model as well as for some non-standard cases. The expected background contribution is indicated by the hatched histogram.

Table 5.8: The expected number of selected events from each of the different processes after the corresponding kinematic fits have been performed. Also shown is the number of actual events selected at 189 GeV.

Selected as	${\rm W}^{+}{\rm W}^{-}\rightarrow{\rm q}\bar{\rm q}\ell\bar{\nu}_{\ell}$
Efficiency [%]	78.7 $\pm$ 1.1
Signal events	1053 $\pm$25
4-fermion, TGC-dep.	11 $\pm$ 3
4-fermion, TGC-indep.	16 $\pm$ 3
Z $^{0}/\gamma\rightarrow{\rm f}\bar{\rm f}$	27 $\pm$ 4
Two-photon	1 $\pm$ 1
Total Background	55 $\pm$ 6
Total expected	1108 $\pm$ 27
Observed	1075

Figure 5.9: Distributions of the kinematic variables $\cos\theta_{\rm W}$, $\cos\theta^{*}_{l}$, $\cos\theta^{*}_{\rm jet}$, $\phi^{*}_{l}$ and $\phi^{*}_{\rm jet}$, as obtained from the ${\rm q}\bar{\rm q}\ell\bar{\nu}_{\ell}$ events. The points represent the data. The histograms show the expectation of the Standard Model and the cases $\Delta g^{z}_{1} = \pm0.5$. The shaded histogram shows the non- ${\rm q}\bar{\rm q}\ell\bar{\nu}_{\ell}$ background. In the case of the W$^{+}$ decaying to the lepton, the value of $\phi^{*}_{l}$ is shifted by $\pi$ in order to overlay the W$^{+}$ and W$^{-}$ distributions.