| Since 1996, the Large Electron-Positron collider (LEP) at CERN has run at energies sufficiently high for the pair production of electroweak gauge bosons. This permits stringent new tests of the Standard Model of particle physics, which makes very precise predictions of the force and nature of the couplings between these bosons. Two of the possible production processes for W+W-- pairs are e+e -- → Z0/gamma → W+W --, which involve W+W--Z 0 and W+W--gamma couplings. A detailed study of W+W-- events can be used to verify the non-Abelian nature of electroweak interactions, and also, eventually, to probe for phenomena arising from physics beyond the Standard Model. The existence of certain new heavy particles, for example, might result in anomalous couplings.;We measure the W+W--Z0 and W+W--gamma couplings directly, from the rate of W+W-- production in the OPAL detector and from characteristics of the decay product distributions of these events. There are three possible final states for W+W -- decays: (i) two oppositely charged leptons and missing energy (W+W-- → ℓ -- n&d1; ℓ+ n ); (ii) one charged lepton, two jets and missing energy (W+W-- → qq¯ℓ n&d1; ); or (iii) four hadronic jets (W+W -- → qq¯qq¯). This thesis principally describes the four-jet decays. This is a complicated final state to reconstruct, as the kinematics of the event must be used to determine which of three possible jet pairings corresponds to the true W+ and W-- , and in order to increase the sensitivity to anomalous couplings, it is also necessary to use the charges and momenta of the hadrons in the jets to reconstruct the charge of each W. The angular distributions of the W+/- and of their decay products are directly related to the helicities of the Ws, and provide an insight into the nature of the gauge boson couplings. |
