Tauoni

Tauoni, also known in English as tauons, are elementary particles in the Standard Model. They are the heaviest charged leptons, forming the third generation of leptons alongside the electron and muon. They carry electric charge −1 and have spin 1/2. Like other leptons, tauoni do not carry color charge and interact via the weak and electromagnetic forces, as well as gravity, but not via the strong interaction.

The tauoni have a rest mass of about 1776.86 MeV/c^2 and a very short mean lifetime of roughly 2.9×10−13 seconds. They decay to lighter particles through the weak interaction. About 65% of tauoni decays are hadronic, producing one or more hadrons plus a tau neutrino; the remaining decays are leptonic, yielding an electron or muon together with corresponding neutrinos.

Representative decay modes include tau → e νe ντ, tau → μ νμ ντ, and hadronic channels such as tau → π− ντ, tau → ρ− ντ, and tau → a1− ντ, among others. The hadronic decays proceed through transitions to up-down quark pairs mediated by the W− boson. Tauoni can be produced in high-energy processes such as electron–positron annihilation to tau+tau− pairs, hadron collisions producing tau pairs, and decays of heavier particles like the Z boson.

The tauoni were discovered in 1975 by Martin Perl and colleagues at the SLAC Stanford Linear Accelerator Center. The discovery confirmed a third-generation charged lepton and contributed to the development of the Standard Model. The tau neutrino, the corresponding neutrino, was confirmed later.

Nomenclature varies by language; the term tauon is traditional, with tauoni used as a plural in some contexts. In modern English usage, tauons is common, while tauon remains standard in some other languages or older literature.