e+e- -> W+W- -> mu+ + tau- -> pi- + pi+ + pi-
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This is an event where a W+W- pair is formed in this collision, one of which then decays to a muon (red) and a neutrino, and the other to a tau and a neutrino. The tau itself decays into three hadrons (green) and a neutrino. All the neutrinos escape from the detector without being detected.

Particle Physics Education CD-ROM 1999 CERN