The event selection efficiency and background contamination were estimated using Monte Carlo. The production of tau-pair events at the resonance was simulated using the KORALZ 3.8 Monte Carlo generator. The same program was used to generate muon-pair events, while wide-angle Bhabha scattering, two-photon interactions, and final states were produced using the generators described in Refs. , , and , respectively. All these Monte Carlo data samples were subjected to the SLD detector simulation based on the GEANT 3.15 program and to the above event selection. The SLD trigger was also simulated in the Monte Carlo.
We determine a tau-pair event selection efficiency of , where the largest loss is due to the solid angle coverage of the CDC. The trigger efficiency is found to be , and the result is an overall selection efficiency of . Based on these estimates, the measured integrated luminosity, and the branching fraction, we expect a final tau sample of events, including backgrounds. This is consistent with the 1671 tau-pair candidate events selected in the data. From the fraction of Monte Carlo background events which survive the selection requirements, the purity of the tau sample is estimated to be . The accuracy of these estimates was checked by comparing data and Monte Carlo distributions for various quantities used in the event selection.