Tauons

Tauons, or tau leptons, are elementary particles belonging to the third generation of leptons. They are the charged cousins of the electron and muon with electric charge -1. The tau is much heavier, with a mass of about 1.776 GeV/c^2, and a spin of 1/2. Like other leptons, tauons interact via the electromagnetic and weak forces but do not participate in the strong interaction. Each tauon has a corresponding neutrino, the tau neutrino ντ.

Tauons are unstable and decay through the weak interaction. The mean lifetime is about 2.9×10^-13 seconds. They decay to leptons (electron or muon) plus neutrinos, or to hadrons plus a neutrino. Approximately 35% of decays are leptonic (roughly half to e νe ντ and half to μ νμ ντ), and about 65% are hadronic, typically involving one or more pions plus a ντ.

Tauons are produced in high-energy processes, such as electron-positron annihilation at high energies where Z bosons decay to τ+τ−, hadron collider processes, and in decays of heavier particles like W bosons or heavy flavor mesons. The tau neutrino was confirmed experimentally in 2000.

History: The tau lepton was discovered in 1975 by Martin Perl and collaborators at the SLAC SPEAR facility. The particle’s existence completed the third generation of charged leptons and provided a crucial test bed for lepton universality and the structure of weak interactions.

Notes: The study of tauons continues to inform precision tests of the Standard Model and searches for new physics, including rare decays and potential lepton-flavor-violating processes.