W+W- production and triple gauge boson couplings at LEP energies up to 183 GeV

TL;DR

This paper reports on W-pair production and triple gauge boson couplings at LEP energies up to 183 GeV, confirming consistency with the Standard Model through cross-section, branching fractions, and polarization measurements.

Contribution

It provides the first measurement of W-pair production cross-section and triple gauge couplings at 183 GeV, with combined analysis from multiple energies and decay channels.

Findings

W-pair production cross-section measured as 15.43 pb

W branching fraction to hadrons is 67.9%

W bosons' longitudinal polarization fraction is 0.242

Abstract

A study of W-pair production in e+e- annihilations at Lep2 is presented, based on 877 W+W- candidates corresponding to an integrated luminosity of 57 pb-1 at sqrt(s) = 183 GeV. Assuming that the angular distributions of the W-pair production and decay, as well as their branching fractions, are described by the Standard Model, the W-pair production cross-section is measured to be 15.43 +- 0.61 (stat.) +- 0.26 (syst.) pb. Assuming lepton universality and combining with our results from lower centre-of-mass energies, the W branching fraction to hadrons is determined to be 67.9 +- 1.2 (stat.) +- 0.5 (syst.)%. The number of W-pair candidates and the angular distributions for each final state (qqlnu,qqqq,lnulnu) are used to determine the triple gauge boson couplings. After combining these values with our results from lower centre-of-mass energies we obtain D(kappa_g)=0.11+0.52-0.37, D(g^z_1)=0.01+0.13-0.12 and lambda=-0.10+0.13-0.12, where the errors include both statistical and systematic uncertainties and each coupling is determined setting the other two couplings to the Standard Model value. The fraction of W bosons produced with a longitudinal polarisation is measured to be 0.242+-0.091(stat.)+-0.023(syst.). All these measurements are consistent with the Standard Model expectations.