Force carrier
In particle physics, the quantum field theory called the Standard Model describes the strong, weak and electromagnetic fundamental forces. In such theories, each type of interaction has a characteristic set of force, or field carrier particles associated with quantum excitation of the force field related to that interaction. These kinds of particles are always exchanged between matter.
The carrier particles either appear in intermediate stages or are produced during all particle processes involving that type of interaction. Forces between particles can be described in terms of static force fields and exchanges of force carrier particles between the affected particles.
The force carriers of the Standard Model are bosons, known as gauge bosons:
- Gluons mediating the strong interactions
- Photons mediating the electromagnetic interactions
- W and Z bosons mediating the weak interactions
The name for the carrier particle of gravitational interactions is the graviton. The status of this particle is still tentative, because the theory is incomplete and there has been no good experimental evidence that they exist (though this does not demonstrate that they do not in fact exist). Gravitons are not considered to be a part of the Standard Model.
In the Standard Model the hypothetical Higgs boson, which is needed to account for the masses of fundamental particles, interacts via the weak interaction and Yukawa interactions but is not a force carrier.
Overview
All elementary particles are either bosons or fermions (depending on their spin). The spin-statistics theorem identifies the resulting quantum statistics that differentiate fermions and bosons.
Interaction of virtual bosons with real fermions are called fundamental interactions. Momentum conservation in these interactions mathematically results in all forces we know. The bosons involved in these interactions are called gauge bosons - such as the W vector bosons of the weak force, the gluons of the strong force, the photons of the electromagnetic force, and (in theory, unconfirmed) the graviton of the gravitational force.
History
The concept of messenger particles dates back to the 18th century when French Physicist Charles Coulomb showed that the electrostatic force between electrically charged objects follows a law similar to Newton's law of gravitation. In time, this relation became known as Coulomb's law. By 1862, Hermann von Helmholtz had described a ray of light as the “quickest of all the messengers”. In 1905, Albert Einstein proposed the existence of a light-particle in answer to the question: “what are light quanta?” In 1923, through the work of Arthur Compton at Washington University in St. Louis, Einstein’s light-particle idea was made undeniably plain to physicists. Lastly, in 1926, one year before the theory of quantum mechanics was completed, Gilbert N. Lewis introduced the term “photon”, which subsequently became the name for Einstein’s light particle. From here the concept of messenger particles developed further.
See also
External links
- Messenger Particles - Cern Interactive Slide Show