Composition | Elementary particle |
---|---|
Statistics | Fermionic |
Generation | Third |
Interactions | Gravity, Electromagnetic, Weak |
Symbol | τ− |
Antiparticle | Antitau ( τ+ ) |
Discovered | Martin Lewis Perl et al. (1975) |
Mass | 776.82±0.16 MeV/c2 1 |
Mean lifetime | ×10−13 s 2.906(10) |
Electric charge | −1 e |
Color charge | None |
Spin | 1/2 |
Weak isospin | LH: −1/2, RH: 0 |
Weak hypercharge | LH: -1, RH: −2 |
The tau (τ), also called the tau lepton, tau particle, or tauon, is an elementary particle similar to the electron, with negative electric charge and a spin of 1/2. Together with the electron, the muon, and the three neutrinos, it is a lepton. Like all elementary particles with half-integer spin, the tau has a corresponding antiparticle of opposite charge but equal mass and spin, which in the tau's case is the antitau (also called the positive tau). Tau particles are denoted by
τ−
and the antitau by
τ+
.
Tau leptons have a lifetime of ×10−13 s and a 2.9mass of 776.82 MeV/c2 (compared to 1 for muons and 105.7 MeV/c2 for electrons). Since their interactions are very similar to those of the electron, a tau can be thought of as a much heavier version of the electron. Because of their greater mass, tau particles do not emit as much 0.511 MeV/c2bremsstrahlung radiation as electrons; consequently they are potentially highly penetrating, much more so than electrons. However, because of their short lifetime, the range of the tau is mainly set by their decay length, which is too small for bremsstrahlung to be noticeable: their penetrating power appears only at ultra high energy (above PeV energies).