Measurement of Electroweak Parameters Using the Muon Pair Charge Asymmetry at OPAL

The forward backward charge asymmetry of the reaction e e is studied at energies close to the Z peak using the OPAL detector at LEP This analysis goes beyond the usual published analyses by taking into account estimates of initial state radiation By using a maximum likelihood t that includes the initial state radiation energy of each event an improved determination of the Z couplings is made The results obtained are g v and g a where the rst error on g a is statistical and the second is systematic These findings are in good agreement with the Standard Model predictions In addition the muon pair trigger efficiency is investigated The trigger is found to be robust and reliable for triggering muon pairs and an efficiency of was determined.