The tauon , also τ-lepton , tau-lepton or τ-particle , is the heaviest of the three charged leptons of the standard model of elementary particles . Its mass is 1777 MeV / c 2 and thus about 3500 times the mass of its light sister particle, the electron . Its mean lifespan is about 0.29 picoseconds, making it significantly more unstable than a muon .
Name and discovery
The name Tauon , or the letter τ , was chosen after the Greek word for third (τρίτον, tríton ), because the τ lepton is the third charged electron-like particle. It was discovered in 1975 by Martin L. Perl and his colleagues at SLAC during electron-positron collisions in the SPEAR ring. For this discovery in particular, Perl received the Nobel Prize in Physics in 1995 .
Decay
Feynman diagram of the most common decay channels, which applies
The τ-lepton can decay into the lighter leptons
as well as in different hadrons , e.g. B. pions or kaons . Here is a selection of the numerous decay channels:
The quark composition of the most commonly involved mesons is:
These mesons are pseudoscalar mesons with total spin 0 and odd parity . It can also vector meson with total spin 1 and odd parity arise, such. B. this :
^ Martin L. Perl: Evidence for, and properties of, the new charged heavy lepton. In: Tran Thanh Van (ed.): Proceedings of the XII Rencontre de Moriond. 1977. (SLAC-PUB-1923, PDF ).