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PARTICLE CLASSIFICATION

ELEMENTARY PARTICLES Particle Anti- Rest mass Lifetime Category name Symbol particle (MeV/c^2) (s) -------- ----------------- --------- --------- --------- -------- Photon Photon gamma -- 0 stable

Leptons Electron e- e+ 0.511 stable Electron neutrino nu|e _nu|e 0 * stable Muon mu- mu+ 105.7 2.20e-6 Muon neutrino nu|mu _nu|mu 0 * stable Tau tau- tau+ 1784 < 4e-13 Tau neutrino nu|tau _nu|tau 0 * stable

Hadrons: Mesons Pion pi+ pi- 139.6 2.60e-8 pi0 -- 135.0 0.83e-16 Kaon K+ K- 493.7 1.24e-8 K0|S _K0|S 497.7 0.89e-10 K0|L _K0|L 497.7 5.2e-8 Eta eta0 -- 548.8 < 1e-18 D D+ D- 1869 9e-13 D0 _D0 1865 5e-13 F F+ F- 2021 ~ 2e-13 J/psi J/psi -- 3097 ~ 1e-20 Psi' psi' -- 3686 ~ 3e-20 Upsilon upsilon -- 9460 ~ 1e-20 B B+ B- 5271 ~ 1e-13 B0 _B0 5274 ~ 1e-13

Baryons Proton p _p 938.3 stable ** Neutron n _n 939.6 920 Lambda lambda0 _lambda0 1115.6 2.6e-10 Sigma sigma+ _sigma- 1189.4 0.80e-10 sigma0 _sigma0 1192.5 6e-20 sigma- _sigma+ 1197.3 1.5e-10 Xi xi0 _xi0 1315 2.9e-10 xi- xi+ 1321 1.64e-10 Omega omega- omega+ 1672 0.82e-10 Lambda|C lambda+|C lambda-|C 2280 1e-13

FUNDAMENTAL PARTICLES Class Name Symbol Charge Mass (MeV/c^2) Discovered ------- ----------------- ------ ------ -------------- ---------- Quarks Up u 2/3 ~ 100 1963 Down d -1/3 ~ 100 1963 Charm c 2/3 ~ 4000 1974 Strange s -1/3 ~ 500 1964 Top t 2/3 3-5000 ? *** Bottom b -1/3 ~ 5000 1977

Leptons Electron neutrino nu|e 0 0 * 1955 Electron e -1 0.511 1898 Muon neutrino nu|mu 0 0 * 1962 Muon mu -1 106 1936 Tau neutrino nu|tau 0 0 * *** Tau lepton tau -1 1784 1975

Field Photon gamma 0 0 1905 quanta (electromagnetic) Intermediate W+/- 0 80 800 1983 vector bosons Z0 0 92 600 1984 (weak) Gluon (strong) -- 0 ? *** Graviton -- 0 0 *** (gravity)

* Physicists have not decisively shown whether or not neutrinos have mass.

** Grand unified theories predict that protons are unstable and decay; but experiments have shown that, should this be true, the decay rate can be no shorter than 2e32 yr.

*** No discovery date; the named particle has been theorized, but has not yet been experimentally found.

NOTES: On particle symbology: A letter (or Greek letter name) is the name of the particle; a +, -, or 0 after the particle indicates a superscripted charge; a | followed by a letter indicates a subscript; and a _ before indicates a bar on top of the particle. For instance, e- indicates an electron, or

- e

while _K0|S indicates __ 0 K S

-)(-