Measurement of triple-gauge-boson couplings of the W boson at LEP

Abstract

The CP-conserving triple-gauge-boson couplings, g₁^Z, κ_γ, λ_γ, g₅^Z, κ_Z and λ_Z are measured using hadronic and semi-leptonic W-pair events selected in 629 pb^-1 of data collected at LEP with the L3 detector at centre-of-mass energies between 189 and 209 GeV. The results are combined with previous L3 measurements based on data collected at lower centre-of-mass energies and with the results from single-W production and from events with a single-photon and missing energy. Imposing the constraints κ_Z=g₁^Z-tan²θ_W(κ _γ-1) and λ_Z=λ_γ, we obtain for the C and P conserving couplings the results: g₁^Z=0.966±0.033(stat)±0.015(syst), κ _γ=1.013±0.066(stat) ±0.026(syst),λ_γ=-0.021±0.035(stat)±0.017(syst).Results from the analysis of fully leptonic W-pair decays are also given. All results are in agreement with the Standard Model expectations and confirm the existence of self-couplings among electroweak gauge bosons.