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Standard Model of Elementary Particles and Forces

Physics experiments of the past hundred years have revealed the atom's structure, with its nucleus and orbiting electrons. Today's experiments use powerful particle accelerators to explore the deepest substructure of matter, the particles and forces inside the proton and neutron of the atom's nucleus. Decades of research have now given us a remarkably simple theoretical model of the elementary particles and forces of matter.

The discovery of the top quark at Fermilab in March, 1995, provided strong evidence for the Standard Model, the prevailing theory that describes the elementary particles and forces. These particles are the matter particles called leptons and quarks; and the force-carrying particles called bosons.

  • The six leptons include the electron, the muon, and the tau; and three neutral particles postulated to be massless --the electron neutrino, the muon neutrino, and the tau neutrino.

  • The six quarks include the up and down quarks that make up the proton and neutron, as well as the strange, charm, bottom, and top quarks that were present at the birth of the universe and that we now produce in particle collisions.

  • The gauge bosons include the gluon that transmits the strong force that holds quarks together in the nucleus; the W and Z bosons that transmit the weak nuclear force responsible for radioactive decay; and the photon that transmits electromagnetic force.

  • Chart of the Standard Model
  • Beyond the Standard Model
  • More information on the Standard Model


  • last modified 07/18/2000   email Fermilab