In particle physics, a gauge boson is a force carrier, a bosonic particle that carries any of the fundamental interactions of nature, commonly called forces.[1][2] Elementary particles, whose interactions are described by a gauge theory, interact with each other by the exchange of gauge bosons—usually as virtual particles.

All known gauge bosons have a spin of 1; for comparison, the Higgs boson has spin zero. Therefore, all known gauge bosons are vector bosons.

Gauge bosons are different from the other kinds of bosons: first, fundamental scalar bosons (the Higgs boson); second, mesons, which are composite bosons, made of quarks; third, larger composite, non-force-carrying bosons, such as certain atoms.

Gauge bosons in the Standard Model

The Standard Model of particle physics recognizes four kinds of gauge bosons: photons, which carry the electromagnetic interaction; W and Z bosons, which carry the weak interaction; and gluons, which carry the strong interaction.[3]

Isolated gluons do not occur because they are colour-charged and subject to colour confinement.

Multiplicity of gauge bosons

In a quantized gauge theory, gauge bosons are quanta of the gauge fields. Consequently, there are as many gauge bosons as there are generators of the gauge field. In quantum electrodynamics, the gauge group is U(1); in this simple case, there is only one gauge boson, the photon. In quantum chromodynamics, the more complicated group SU(3) has eight generators, corresponding to the eight gluons. The three W and Z bosons correspond (roughly) to the three generators of SU(2) in GWS theory.

Massive gauge bosons

For technical reasons[which?] involving gauge invariance, gauge bosons are described mathematically by field equations for massless particles. Therefore, at a naïve theoretical level, all gauge bosons are required to be massless, and the forces that they describe are required to be long-ranged. The conflict between this idea and experimental evidence that the weak and strong interactions have a very short range requires further theoretical insight.

According to the Standard Model, the W and Z bosons gain mass via the Higgs mechanism. In the Higgs mechanism, the four gauge bosons (of SU(2)×U(1) symmetry) of the unified electroweak interaction couple to a Higgs field. This field undergoes spontaneous symmetry breaking due to the shape of its interaction potential. As a result, the universe is permeated by a nonzero Higgs vacuum expectation value (VEV). This VEV couples to three of the electroweak gauge bosons (the Ws and Z), giving them mass; the remaining gauge boson remains massless (the photon). This theory also predicts the existence of a scalar Higgs boson, which has been observed in experiments at the LHC.[4]

Beyond the Standard Model

Grand unification theories

The Georgi–Glashow model predicts additional gauge bosons named X and Y bosons. The hypothetical X and Y bosons mediate interactions between quarks and leptons, hence violating conservation of baryon number and causing proton decay. Such bosons would be even more massive than W and Z bosons due to symmetry breaking. Analysis of data collected from such sources as the Super-Kamiokande neutrino detector has yielded no evidence of X and Y bosons.

Gravitons

The fourth fundamental interaction, gravity, may also be carried by a boson, called the graviton. In the absence of experimental evidence and a mathematically coherent theory of quantum gravity, it is unknown whether this would be a gauge boson or not. The role of gauge invariance in general relativity is played by a similar symmetry: diffeomorphism invariance.

W' and Z' bosons

Main article: W' and Z' bosons

W' and Z' bosons refer to hypothetical new gauge bosons (named in analogy with the Standard Model W and Z bosons).

See also

1964 PRL symmetry breaking papers

Boson

Glueball

Quantum chromodynamics

Quantum electrodynamics

References

Gribbin, John (2015). Q is for Quantum – An Encyclopedia of Particle Physics. Simon & Schuster. ISBN 0-684-85578-X.

Clark, John, E.O. (2004). The Essential Dictionary of Science. Barnes & Noble. ISBN 0-7607-4616-8.

Veltman, Martinus (2003). Facts and Mysteries in Elementary Particle Physics. World Scientific. ISBN 981-238-149-X.

"CERN and the Higgs boson". CERN. Archived from the original on 23 November 2016. Retrieved 23 November 2016.

External links

Explanation of gauge boson and gauge fields by Christopher T. Hill

vte

Particles in physics

Elementary

Fermions

Quarks

Up (quark antiquark) Down (quark antiquark) Charm (quark antiquark) Strange (quark antiquark) Top (quark antiquark) Bottom (quark antiquark)

Leptons

Electron Positron Muon Antimuon Tau Antitau Electron neutrino Electron antineutrino Muon neutrino Muon antineutrino Tau neutrino Tau antineutrino

Bosons

Gauge

Scalar

Hypothetical

Superpartners

Gauginos

Others

Axino Chargino Higgsino Neutralino Sfermion (Stop squark)

Others

Axion Curvaton Dilaton Dual graviton Graviphoton Graviton Inflaton Leptoquark Magnetic monopole Majoron Majorana fermion Dark photon Planck particle Preon Sterile neutrino Tachyon W′ and Z′ bosons X and Y bosons

Nucleon

Proton Antiproton Neutron Antineutron Delta baryon Lambda baryon Sigma baryon Xi baryon Omega baryon

Mesons

Pion Rho meson Eta and eta prime mesons Phi meson J/psi meson Omega meson Upsilon meson Kaon B meson D meson Quarkonium

Exotic hadrons

Others

Atomic nuclei Atoms Exotic atoms

Positronium Muonium Tauonium Onia Pionium Superatoms Molecules

Hypothetical

Baryons

Hexaquark Heptaquark Skyrmion

Mesons

Others

Mesonic molecule Pomeron Diquark R-hadron

Anyon Davydov soliton Dropleton Exciton Hole Magnon Phonon Plasmaron Plasmon Polariton Polaron Roton Trion

Lists

Baryons Mesons Particles Quasiparticles Timeline of particle discoveries

Related

History of subatomic physics

timeline Standard Model

mathematical formulation Subatomic particles Particles Antiparticles Nuclear physics Eightfold way

Quark model Exotic matter Massless particle Relativistic particle Virtual particle Wave–particle duality Particle chauvinism

Wikipedia books

Hadronic Matter Particles of the Standard Model Leptons Quarks

vte

Standard Model

Background

Particle physics

Fermions Gauge boson Higgs boson Quantum field theory Gauge theory Strong interaction

Color charge Quantum chromodynamics Quark model Electroweak interaction

Weak interaction Quantum electrodynamics Fermi's interaction Weak hypercharge Weak isospin

Constituents

CKM matrix Spontaneous symmetry breaking Higgs mechanism Mathematical formulation of the Standard Model

Beyond the

Standard Model

Evidence

Hierarchy problem Dark matter Cosmological constant problem Strong CP problem Neutrino oscillation

Theories

Technicolor Kaluza–Klein theory Grand Unified Theory Theory of everything

MSSM Superstring theory Supergravity

String theory Loop quantum gravity Causal dynamical triangulation Canonical quantum gravity Superfluid vacuum theory Twistor theory

Experiments

Gran Sasso INO LHC SNO Super-K Tevatron

Hellenica World - Scientific Library

Retrieved from "http://en.wikipedia.org/"

All text is available under the terms of the GNU Free Documentation License