Measurement of Triple-Gauge-Boson Couplings of the W Boson at LEP

TL;DR

This paper measures the triple-gauge-boson couplings of the W boson at LEP, confirming Standard Model predictions and providing precise constraints on these couplings through analysis of W-pair events.

Contribution

It presents the first comprehensive measurement of multiple W boson couplings at LEP, combining various datasets and decay channels for improved precision.

Findings

Results are consistent with Standard Model predictions.

Precise values for g1Z, kappa_gamma, and lambda_gamma couplings.

Confirmation of electroweak gauge boson self-couplings.

Abstract

The CP-conserving triple-gauge-boson couplings, g1Z, kappa_gamma, lambda_gamma, g5Z, kappa_Z and lambda_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 kappa_Z = g1Z - tan^2(theta_W) (kappa_gamma-1) and lambda_Z = lambda_gamma, we obtain for the C and P conserving couplings the results: g1Z = 0.966 +/- 0.033 (stat.) +/- 0.015 (syst.) kappa_gamma = 1.013 +/-0.066 (stat.) +/- 0.026 (syst.) lambda_gamma = -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.