Electric charge: +2/3
Mass: 2.3 MeV
Constituent of ordinary matter; two up quarks, plus a down, make up a proton.
Mass: 1.28 GeV*
Unstable heavier cousin of the up; constituent of the J/ψ particle, which helped physicists develop the Standard Model.
Mass: 173.5 GeV*
Heaviest known particle, comparable in mass to an atom of osmium. Very short-lived.
Electric charge: –1/3
Mass: 4.8 MeV
Constituent of ordinary matter; two down quarks, plus an up, compose a neutron.
Mass: 95 MeV
Unstable heavier cousin
of the down; constituent of the much studied kaon particle.
Mass: 4.18 GeV*
Unstable and still heavier
copy of the down; constituent
of the much studied B-meson particle.
Electric charge: 0
Immune to both electromagnetism and the strong force, it barely interacts
at all but is essential to radioactivity.
Appears in weak reactions involving the muon.
Appears in weak reactions involving the tau lepton.
Electric charge: –1
Mass: 0.511 MeV
The lightest charged particle, familiar as the carrier of electric currents and the particles orbiting atomic nuclei.
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.
Mass: 1.78 GeV*
Another unstable and still heavier version of the electron, with a lifetime of 0.3 picosecond.
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.
Eight species of gluons carry the strong interaction, acting on quarks and on other gluons. They do not feel electromagnetic or weak interactions.
Mass: 91.2 GeV*
Mediator of weak reactions that do not change the identity of particles. Its range is only about 10–18 meter.
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.
Mass: ~125 GeV*
Believed to endow W and Z bosons, quarks and leptons with mass.