Measurement of W-pair cross sections in e+e− interactions at s=183GeV and W-decay branching fractions

We report on the measurement of W-boson pair-production with the L3 detector at LEP. In a data sample corresponding to a total luminosity of 55.47 pb−1 collected at an average centre-of-mass energy of 182.68GeV, we select 824 four-fermion events with pairs of hadronic jets or pairs of leptons with high invariant masses. Branching fractions of W decays into different fermion-antifermion pairs are determined. Assuming charged-current lepton universality, the branching fraction for hadronic W decays is measured to be: B(W→hadrons)=70.1±1.3(stat.)±0.4(syst.)%. Combining all final states the total cross section for W-pair production is measured to be: σWW=16.53±0.67(stat.)±0.26(syst.) pb.