Using about 3.9 million hadronic Z decays from e(+)e(-) collisions recorded
by the OPAL detector at LEP at centre-of-mass energies,roots approximate t
o M-Z, the branching ratio for the decay D-s(-)--> tau (-)(v) over bar (tau
) has been measured to be BR(D-s(-) --> tau (-)(v)over bar>) = (7.0 +/- 2.1
(stat) +/- 2.0(syst))%. This result can be used to derive the decay constan
t of the D-s(-) meson: f(Ds) = (286 +/- 44(stat) +/- 41 (syst)) MeV. (C) 20
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