Measurement of the Cross Section of W-boson pair production at LEP

TL;DR

This paper reports a precise measurement of the W-boson pair-production cross section at LEP, confirming Standard Model predictions and providing detailed decay and angular distribution data.

Contribution

First precise measurement of W-boson pair-production cross section at LEP energies, confirming Standard Model predictions and measuring decay branching fractions and angular distributions.

Findings

Total cross section measured with 1.4% precision

Branching fraction for hadronic W decays: 67.50%

Differential cross sections as a function of W production angle

Abstract

The cross section of W-boson pair-production is measured with the L3 detector at LEP. In a data sample corresponding to a total luminosity of 629.4/pb, collected at centre-of-mass energies ranging from 189 to 209 GeV, 9834 four-fermion events with W bosons decaying into hadrons or leptons are selected. The total cross section is measured with a precision of 1.4 % and agrees with the Standard Model expectation. Assuming charged-lepton universality, the branching fraction for hadronic W-boson decays is measured to be: Br(W-->hadrons) = 67.50 +- 0.42 (stat.) +- 0.30(syst.) %, in agreement with the Standard Model. Differential cross sections as a function of the W- production angle are also measured for the semi-leptonic channels qqev and qqmv.