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Fundamental interactions and mediator fields

The Standard Model describes three nongravitational fundamental interactions through quantum fields.

Electromagnetism acts on electric charge and is mediated by the photon. It is long-ranged because the photon is massless.

The strong interaction acts on color charge. Its gauge bosons are eight gluons, which themselves carry color and interact with one another. At short distances the interaction becomes weaker, while at ordinary hadronic scales quarks and gluons are confined into color-neutral hadrons.

The weak interaction changes particle flavor and is mediated by the massive $W^+$, $W^-$ and $Z^0$ bosons. Its short range is associated with the large mediator masses. Beta decay is a low-energy manifestation of the weak interaction.

Gravity is fundamental but is not included in the Standard Model quantum field theory. At particle scales its direct strength is normally negligible compared with the other interactions.

Interaction diagrams often depict exchange of mediator particles, but a mediator should not be imagined as a classical projectile literally shuttling a force back and forth. In quantum field theory, particles are excitations of fields and interaction amplitudes are calculated from allowed couplings among those fields.

The interaction a particle experiences is determined by its charges and quantum numbers: neutrinos feel the weak interaction but not electromagnetism or the strong interaction; quarks participate in all three Standard Model interactions.