Gauge boson certain atoms. The Standard Model of particle physics recognizes four kinds of gauge bosons: photons, which carry the electromagnetic interaction; W and Z bosons, which carry the weak interaction; and gluons, which carry the strong interaction. Isolated gluons do not occur because they are color-charged and subject to color confinement. In a quantized gauge theory, gauge bosons are quanta of the gauge fields. Consequently, there are as many gauge bosons as there are generators of the gauge field. In quantum electrodynamics, the gauge group is "U"(1); in this simple case, there is only one gauge boson. In quantum chromodynamics, the
Elementary particle Elementary particle In particle physics, an elementary particle or fundamental particle is a with no substructure, thus not composed of other particles. Particles currently thought to be elementary include the fundamental fermions (quarks, leptons, antiquarks, and antileptons), which generally are "matter particles" and "antimatter particles", as well as the fundamental bosons (gauge bosons and the Higgs boson), which generally are "force particles" that mediate interactions among fermions. A particle containing two or more elementary particles is a "composite particle". Everyday matter is composed of atoms, once presumed to be matter's elementary particles—"atom" meaning "unable to cut" in Greek—although the atom's