In particle physics, the tau is the third generation lepton. It's very massive and thus requires very high-energy collisions to create. The process of creating taus usually involves colliding beams of electrons and positrons (antielectrons). At high enough energies, this results in the production of tau and antitau, which decay almost instantly (in the range of 10-13 seconds).

The tau's corresponding neutrino (the tau neutrino) was recently discovered at Fermilab in Illinois, providing experimental verification for its prediction in the Standard Model.