standard model

In physics, modern theory of elementary particles and their interactions. According to the standard model, elementary particles are classified as leptons (light particles, such as electrons), hadrons (particles, such as neutrons and protons, that are formed from quarks), and gauge bosons. Leptons and hadrons interact by exchanging gauge bosons, each of which is responsible for a different fundamental force: photons mediate the electromagnetic force, which affects all charged particles; gluons mediate the strong nuclear force, which affects quarks; gravitons mediate the force of gravity; and the intermediate vector bosons mediate the weak nuclear force. See also forces, fundamental, quantum electrodynamics, and quantum chromodynamics.