Using a data sample of 57 pb(-1) recorded at a centre-of-mass energy of 183
GeV with the OPAL detector at LEP, 282 W+W- --> q (q) over bar q (q) over
bar and 300 W+W- --> q (q) over bar l<(nu)over bar>(l) candidate events are
used to obtain a measurement of the mass of the W boson, M-W = 80.39 +/- 0
.13 (stat.) +/- 0.05 (syst.) GeV, assuming the Standard Model relation betw
een M-W and Gamma(W). A second fit provides a direct measure of the width o
f the W boson and gives Gamma(W) = 1.96 +/- 0.34 (stat.) +/- 0.20 (syst.) G
eV. These results are combined with previous OPAL results to obtain M-W = 8
0.38 +/- 0.12 (stat.) +/- 0.05 (syst.) GeV and Gamma(W) = 1.84 +/- 0.32 (st
at.) +/- 0.20 (syst.) GeV. (C) 1999 Published by Elsevier Science B.V. All
rights reserved.