Up
Electric charge: +2/3
Mass: 2.3 MeV
Constituent of ordinary matter; two up quarks, plus a down, make up a proton.
X
Charm
Electric charge: +2/3
Mass: 1.28 GeV*
Unstable heavier cousin of the up; constituent of the J/ψ particle, which helped physicists develop the Standard Model.
*GeV: giga-electron-volts
X
Top
Electric charge: +2/3
Mass: 173.5 GeV*
Heaviest known particle, comparable in mass to an atom of osmium. Very short-lived.
*GeV: giga-electron-volts
X
Down
Electric charge: –1/3
Mass: 4.8 MeV
Constituent of ordinary matter; two down quarks, plus an up, compose a neutron.
X
Strange
Electric charge: –1/3
Mass: 95 MeV
Unstable heavier cousin
of the down; constituent of the much studied kaon particle.
X
Bottom
Electric charge: –1/3
Mass: 4.18 GeV*
Unstable and still heavier
copy of the down; constituent
of the much studied B-meson particle.
*GeV: giga-electron-volts
X
Electron Neutrino
Electric charge: 0
Immune to both electromagnetism and the strong force, it barely interacts
at all but is essential to radioactivity.
X
Muon Neutrino
Electric charge: 0
Appears in weak reactions involving the muon.
X
Tau Neutrino
Electric charge: 0
Appears in weak reactions involving the tau lepton.
X
Electron
Electric charge: –1
Mass: 0.511 MeV
The lightest charged particle, familiar as the carrier of electric currents and the particles orbiting atomic nuclei.
X
Muon
Electric charge: –1
Mass: 105.7 MeV
A heavier version of the electron, with a lifetime of 2.2 microseconds; discovered as a component of cosmic-ray showers.
X
Tau
Electric charge: –1
Mass: 1.78 GeV*
Another unstable and still heavier version of the electron, with a lifetime of 0.3 picosecond.
*GeV: giga-electron-volts
X
Photon (electromagnetism)
Electric charge: 0
Mass: 0
Carrier of electromagnetism, the quantum of light acts on electrically charged particles. It acts over unlimited distances.
Particle Type: Boson
At the quantum level, each force of nature is transmitted by a dedicated particle or set of particles.
X
Gluon (strong force)
Electric charge: 0
Mass: 0
Eight species of gluons carry the strong interaction, acting on quarks and on other gluons. They do not feel electromagnetic or weak interactions.
X
z (weak force)
Electric charge: 0
Mass: 91.2 GeV*
Mediator of weak reactions that do not change the identity of particles. Its range is only about 10–18 meter.
*GeV: giga-electron-volts
X
W (weak force)
Electric charge: +1 or –1
Mass: 80.4 GeV*
Mediators of weak reactions that change particle flavor and charge. Their range is only about 10–18 meter.
*GeV: giga-electron-volts
X
Higgs
Electric charge: 0
Mass: ~125 GeV*
Believed to endow W and Z bosons, quarks and leptons with mass.
*GeV: giga-electron-volts
X