A Study Of W Boson Properties With Four-jet $W^{+}w^{-}$ Events At Lep

In this thesis I present a study of W pair production in e+e- annihilation using fully hadronic W+W- events. Data collected by the L3 detector at LEP in 1996-1998, at collision center-of-mass energies between 161 and 189 GeV, was used in my analysis. Analysis of the total and differential W+W- cross sections with the resulting sample of 1,932 W+W- → qqqq event candidates allowed me to make precision measurements of a number of properties of the W boson. I combined my measurements with those using other W+W- final states to obtain stringent constraints on the W boson's couplings to fermions, other gauge bosons, and scalar Higgs field by measuring the total e+e- → W+W- cross section and its energy dependence σ(e+e- → W+W-) = {2.68+0.98-0.67(stat.)± 0.14(syst.) pb, √s = 161.34 GeV {12.04+1.38-1.29(stat.)± 0.23(syst.) pb, √s = 172.13 GeV {16.45 ± 0.67(stat.) ± 0.26(syst.) pb, √s = 182.68 GeV {16.28 ± 0.38(stat.) ± 0.26(syst.) pb, √s = 188.64 GeV the fraction of W bosons decaying into hadrons BR(W →qq') = 68.72 ± 0.69(stat.) ± 0.38(syst.) %, invisible non-SM width of the W boson ΓinvisibleW less than MeV at 95% C.L., the mass of the W boson MW = 80.44 ± 0.08(stat.)± 0.06(syst.) GeV, the total width of the W boson ΓW = 2.18 ± 0.20(stat.)± 0.11(syst.) GeV, the anomalous triple gauge boson couplings of the W ΔgZ1 = 0.16+0.13-0.20(stat.) ± 0.11(syst.) Δkγ = 0.26+0.24-0.33(stat.) ± 0.16(syst.) λγ = 0.18+0.13-0.20(stat.) ± 0.11(syst.) No significant deviations from Standard Model predictions were found in any of the measurements.