Measurement of Neutral-Current Four-Fermion Production at LEP2
  Four-fermion final states qqbar e+e- and qqbar mu+mu- from neutral-current interactions in e+e- collisions are studied in the OPAL detector at LEP at centre-of-mass energies from 183 GeV to 209 GeV. The data analysed correspond to a total integrated luminosity of about 650 pb-1 recorded from 1997 to 2000. Corresponding to the acceptance of the OPAL detector, a signal definition is applied requiring both leptons to have a scattering angle satisfying cos0 <0.95. Further requirements are made on the invariant masses of the fermion pairs. The extracted cross-sections for the processes e+e- -> qqbar e+e- and e+e- qqbar mu+mu- are consistent with the expectations from the Standard Model. 
The OPAL collaboration