Event Display Pictures : Tau-Pair Production
The tau lepton is, like the muon, an even heavier version of an electron,
but the picture of tau pair events (
)
is different from the two cases of lighter leptons (
)
discussed above. The tau particle is so massive that it has a very short
lifetime and will decay almost right away inside the vertex detector.
(Compare this with muons that live long
enough to fly all the way through the detector before they decay. Electrons
are the lightest charged particles and they can never decay, but they
become trapped in the inner calorimeter.)
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Event 11568_1227_500_z_tau |
 Event 27893_1929_600_z_tau |
There are various possible tau decays -- to a muon plus a unseen neutrinos, to an electron plus unseen neutrinos, or to a few hadrons plus a single unseen neutrino. Because the tau was fast-moving, the hadrons are tightly bunched together forming what is called a "jet."
Use your knowledge of track types to figure out how the two taus in the event pictured above must have decayed. (Answer)
