W+W- production cross section and W branching fractions in e+e- collisions at 189 GeV

From a data sample of 183 pb(-1) recorded at a center-of-mass energy of roots=189 GeV with the OPAL detector at LEP, 3068 W-pair candidate events are selected. Assuming Standard Model W boson decay branching fractions, the W-pair production cross section is measured to be sigma (WW) = 16.30 +/- 0.34(stat.) +/- 0.18(syst.) pb. When combined with previous OPAL measurements, the W boson branching fraction to hadrons is determined to be 68.32 +/- 0.61(stat.) +/- 0.28(syst.)% assuming lepton universality. These results are consistent with Standard Model expectations. (C) 2000 Published by Elsevier Science B.V.