Selection Criteria

Tau-pair candidates are required to have at least two but fewer than seven tracks. Each event is divided into hemispheres by the plane normal to the track with the highest momentum. Tracks in each hemisphere must fall within of the net momentum vector in the hemisphere, and the jet invariant mass[9] in each hemisphere is required to be less than 2.3 GeV/c. Furthermore, the jet axes in the two hemispheres must be back-to-back within . These criteria discriminate strongly against background from multi-hadron final states. The polar angle of the missing momentum[9] in each event is required to satisfy to discriminate against two-photon interactions and Bhabha events. Two-prong events are required to have a minimum acolinearity of 10 mrad. The scalar sum of the momenta of the two stiffest tracks in any event must be less than 65 GeV/c. These cuts primarily reject Bhabha events and muon-pair final states.

The total visible energy[9] in an event is required to be at least 12%of the center-of-mass energy () to reject two-photon interactions. To discriminate against Bhabha events, the total energy deposited in the electromagnetic section of the calorimeter is required to be less than , and the most energetic EM cluster must be less than . In addition, the total calorimeter energy not included in identified jets[9] is required to be less than 5 GeV, and there must be fewer than six energy clusters not included in jets.

These criteria resulted in a sample of 1671 tau-pair candidates selected from the 1992 and 1993 data. Further requirements were imposed in each individual lifetime analysis.