The Standard Model of Elementary Particles

The theoretical picture that describes how the elementary particles are organized and how they interact with one another via the forces is called the Standard Model.

Elementary Particles

The table at right shows the three generations of elementary particles known today. Included are six quarks (up, down, strange, charm, bottom, top), six leptons (electron, muon, tau, and a neutrino associated with each of the three), and four types of force-carrying particles, the bosons (photon, gluons, Z, W). Only the quarks feel the effects of the strong nuclear force. The quarks and the leptons are subject to the weak nuclear force. All particles that have electric charge, including the W+ and W-, feel the electromagnetic force.

Composite Particles

The baryons and mesons are made up of quarks bound together by gluons. Baryons range from the proton and neutron, which are constituents of the atomic nucleus, to ever-growing families of "hyperons" and "resonances" at higher energies. Mesons have a quark and an antiquark bound in an "atom-like" system. Some of the more exciting baryons and mesons have at least one heavy quark such as a charm or bottom quark. Certain pairs of mesons like the Ko and anti-Ko are used to study the breaking of the symmetries of the Standard Model, as seen in CP violation.

 

Back to the dictionary