The inclusive charm production rate in W decays is measured from a study of the properties of final state particles. The sample of W pairs is selected from 67.7 pb(-1) collected by ALEPH in 1996 and 1997 at centre-of-mass energies near 172 and 183 GeV in the channels W+W- --> 4q and W+W- --> l . The branching fraction of hadronic W decays to a final state containing a c quark, R-c(W) = Gamma(W --> hadrons), is measured to be 0.51 +/- 0.05(stat) +/- 0.03(syst). This allows a direct determination of the CKM matrix element V-cs = 1.00 +/- 0.11(stat) +/- 0.07(syst). (C) 1999 Published by Elsevier Science B.V. All rights reserved.
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