A test of higher order electroweak theory in Z0 decays to two leptons with an associated pair of charged particles

The OPAL detector at LEP was used to study the reactions e+e− → e+e−V, e+e− → μ+μ−V and e+e− → τ+τ−V, where V represents an additional pair of oppositely charged tracks coming directly from the event vertex. Rates for these processes were determined using selection criteria similar to those described in a recent publication by the ALEPH Collaboration in which a possible excess in the τ+τ−V channel was reported. In the OPAL data no discrepancy …