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The Monte Carlo program for the OPAL experiment at the LEP e + e collider is described.This program is based on the GEANT simulation package. The general organization of the program is outlined, and a description is given of the techniques used for simulating the various subdetectors of OPAL. The performance of the program is illustrated by comparisons with recent data recorded by O P AL at LEP.

We obtain an expression for the anomaly of a general representation of SU(N).

The strong coupling constant, s , has been determined in hadronic decays of the Z 0 resonance, using measurements of seven observables relating to global event shapes, energy correlations and jet rates. The data have been compared with resummed QCD calculations, which are combined with the O(2 s) theory. The seven measurements agree to about 10%, and the nal result, based on a weighted average, is: s (M Z 0) = 0 : 120 0:006 ; where the error includes both experimental and theoretical uncertainties. This value corresponds to renormalization scale = M Z 0 and the error includes the uncertainty in this choice of scale. The present measurement complements previous determinations using the O(2 s) QCD matrix elements alone, and yields a compatible result, with comparable errors.

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