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

A study of W-pair production in e(+)e(-) annihilations at LEP is presented, based on 877 W+W- candidates corresponding to an integrated luminosity of 57 pb(-1) at root 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 (q<(ql)over bar>v(l), q (q) over bar q (q) over bar,<(lv)over bar>(l)l'(v) over bar(l')) are used to determine the triple gauge boson couplings. After combining these values with our results from lower centre-of-mass energies we obtain Delta kappa(gamma), = 0.11(-0.37)(+0.52), Delta g(1)(z) = 0.01(-0.12)+(0.13) and lambda = -0.10(-0.12)(+0.13), where the errors include both statistical and systematic uncertainties and each coupling is determined by 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.