Measurement of the $WWγ$ and $WWZ$ Couplings at LEP200: The Benefits of Higher Energy?

Abstract

We performed a detailed analysis of the process $e^+e^-\to \ell νq\bar{q}'$ to determine its sensitivity to anomalous trilinear gauge boson couplings of the $WWγ$ and $WWZ$ vertices and how the sensitivity varies with energy and integrated luminosity. We included all tree level Feynman diagrams that contribute to this final state and used a maximum likelihood analysis of a five dimensional differential cross-section based on the $W$ and $W$ decay product angular distributions. For constant luminosity, increasing $\sqrt{s}$ from 175~GeV to 192~GeV (220~GeV) improves the measurement sensitivity by a factor of 1.5 to 2 (2 to 3) depending on the parameter measured. However, the lower luminosity expected at higher $\sqrt{s}$ will reduce these improvements. In any case, the sensitivities for $\sqrt{s}$=175~GeV and L=500~pb$^{-1}$ of $δg_1^Z = \pm 0.22$, $δκ_Z = \pm 0.20$, $δκ_γ=\pm 0.27$, $δL_{9L}= \pm 55$, and $δL_{9R}= ^{+330}_{-230}$ are likely to be at least an order of magnitude too big to see the effects of new physics.