On Theoretical Uncertainties of the W Angular Distribution in W-Pair Production at LEP2 Energies

Abstract

We discuss theoretical uncertainties of the distribution in the cosine of the W polar angle projected into a measurement of the anomalous triple gauge-boson coupling \lambda=\lambda_{\gamma}=\lambda_Z at LEP2 energies for the tandem of the Monte Carlo event generators KoralW and YFSWW3 and for the Monte Carlo event generator RacoonWW. Exploiting numerical results of these programs and cross-checks with experimental fitting procedures, we estimate that the theoretical uncertainty of the value of \lambda due to electroweak corrections, as obtained at LEP2 with the help of these programs, is ~0.005, about half of the expected experimental error for the combined LEP2 experiments (~0.010). We use certain idealized event selections; however, we argue that these results are valid for realistic LEP2 measurements.