Barate, R (reprint author), CNRS, LAPP, IN2P3, F-74019 Annecy Le Vieux, France.
The production of W+W- pairs is analysed in a data sample collected by ALEPH at a mean centre-of-mass energy of 182.7 GeV, corresponding to an integrated luminosity of 57 pb(-1). Cross sections are given for different topologies of W decays into leptons or hadrons. Under Standard Model assumptions for the W-pair production and decay, the W-pair cross section is measured to be 15.57 +/- 0.62 (stat.) +/- 0.29 (syst.) ph. Using also the W-pair data samples collected by ALEPH at lower centre-of-mass energies, the decay branching ratio of the W boson into hadrons is measured to be B(W --> hadrons) = 68.93 +/- 1.21 (stat.) +/- 0.51 (syst.)%, allowing a determination of the CKM matrix element /V-cs/ = 1.043 +/- 0.058 (stat.) +/- 0.026 (syst.). The agreement of the cross sections with the Standard Model prediction allows a limit to be set on the W decay rate to undetectable final states. (C) 1999 Published by Elsevier Science B.V. All rights reserved.