The magnitude of the CKM matrix element /V-ub/ is determined by measuring t
he inclusive charmless semileptonic branching fraction of beauty hadrons at
OPAL based on b --> X(u)l nu event topology and kinematics. This analysis
uses OPAL data collected between 1991 and 1995, which correspond to about f
our million hadronic Z decays. We measure Br(b --> X(u)l nu) to be (1.63 +/
-0.53 (+0.15)(-0.62)) X 10(-3). The first uncertainty is the statistical er
ror and the second is the systematic error. From this analysis,. /V-ub/ is
determined to be:
/Vub/ = (4.00 +/-0.65(stat)(-0.76)(+0.67) (sys) +/- 0.19(HQE)) X 10(-3).
The last error represents the theoretical uncertainties related to the extr
action of /V-ub/ from Br(b --> X(u)l nu) using the Heavy Quark Expansion.