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Gauge boson
 
 
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In particle physics
Particle physics

Particle physics is a branch of physics that studies the elementary particle constituents of matter and radiation, and the interactions between them....
, gauge bosons are boson
Boson

In particle physics, bosons are subatomic particle which obey Bose-Einstein statistics; they are named after Satyendra Nath Bose and Albert Einstein....
ic particles that act as carriers of the fundamental force
Fundamental interaction

In physics, a fundamental interaction or fundamental force is a process by which elementary particles interact with each other. An interaction is often described as a field , and is mediated by the exchange of gauge bosons between particles....
s of nature. More specifically, elementary particle
Elementary particle

In particle physics, an elementary particle or fundamental particle is a wiktionary:particle not known to have substructure; that is, it is not known to be made up of smaller particles....
s whose interaction
Interaction

Interaction is a kind of action that occurs as two or more objects have an effect upon one another. The idea of a two-way effect is essential in the concept of interaction, as opposed to a one-way causal effect....
s are described by gauge theory
Gauge theory

In physics, gauge theory is a quantum field theory where the Lagrangian is invariant under certain transformations.The transformations form a Lie group which is referred to as the symmetry group or the gauge group of the theory....
 exert forces on each other by the exchange of gauge bosons, usually as virtual particle
Virtual particle

In physics, a virtual particle is a particle that exists for a limited time and space, introducing uncertainty in their energy and momentum due to the Heisenberg Uncertainty Principle....
s.

he Standard Model
Standard Model

The Standard Model of particle physics is a theory of three of the four known fundamental interactions and the elementary particles that take part in these interactions....
, there are three kinds of gauge bosons:
  1. photons,
  2. W and Z bosons
    W and Z bosons

    The W and Z bosons are the elementary particles that mediate the weak force. Their discovery has been heralded as a major success for the Standard Model of particle physics....
    , and
  3. gluon
    Gluon

    Gluons are elementary particles that cause quarks to interact, and are indirectly responsible for the binding of protons and neutrons together in atomic nuclei....
    s.
Each corresponds to one of the three Standard Model interactions: photons are gauge bosons of the electromagnetic interaction, W and Z bosons carry the weak interaction
Weak interaction

The weak interaction is one of the four fundamental interactions of nature. In the Standard Model of particle physics, it is due to the exchange of the heavy W and Z bosons....
, and the gluons carry the strong interaction
Strong interaction

In particle physics, the strong interaction, or strong force, or color force, holds quarks and gluons together to form protons, neutrons and other particles....
.






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Encyclopedia


In particle physics
Particle physics

Particle physics is a branch of physics that studies the elementary particle constituents of matter and radiation, and the interactions between them....
, gauge bosons are boson
Boson

In particle physics, bosons are subatomic particle which obey Bose-Einstein statistics; they are named after Satyendra Nath Bose and Albert Einstein....
ic particles that act as carriers of the fundamental force
Fundamental interaction

In physics, a fundamental interaction or fundamental force is a process by which elementary particles interact with each other. An interaction is often described as a field , and is mediated by the exchange of gauge bosons between particles....
s of nature. More specifically, elementary particle
Elementary particle

In particle physics, an elementary particle or fundamental particle is a wiktionary:particle not known to have substructure; that is, it is not known to be made up of smaller particles....
s whose interaction
Interaction

Interaction is a kind of action that occurs as two or more objects have an effect upon one another. The idea of a two-way effect is essential in the concept of interaction, as opposed to a one-way causal effect....
s are described by gauge theory
Gauge theory

In physics, gauge theory is a quantum field theory where the Lagrangian is invariant under certain transformations.The transformations form a Lie group which is referred to as the symmetry group or the gauge group of the theory....
 exert forces on each other by the exchange of gauge bosons, usually as virtual particle
Virtual particle

In physics, a virtual particle is a particle that exists for a limited time and space, introducing uncertainty in their energy and momentum due to the Heisenberg Uncertainty Principle....
s.

Standard Model gauge bosons

In the Standard Model
Standard Model

The Standard Model of particle physics is a theory of three of the four known fundamental interactions and the elementary particles that take part in these interactions....
, there are three kinds of gauge bosons:
  1. photons,
  2. W and Z bosons
    W and Z bosons

    The W and Z bosons are the elementary particles that mediate the weak force. Their discovery has been heralded as a major success for the Standard Model of particle physics....
    , and
  3. gluon
    Gluon

    Gluons are elementary particles that cause quarks to interact, and are indirectly responsible for the binding of protons and neutrons together in atomic nuclei....
    s.
Each corresponds to one of the three Standard Model interactions: photons are gauge bosons of the electromagnetic interaction, W and Z bosons carry the weak interaction
Weak interaction

The weak interaction is one of the four fundamental interactions of nature. In the Standard Model of particle physics, it is due to the exchange of the heavy W and Z bosons....
, and the gluons carry the strong interaction
Strong interaction

In particle physics, the strong interaction, or strong force, or color force, holds quarks and gluons together to form protons, neutrons and other particles....
. Due to color confinement, isolated gluons do not occur at low energies. What could result instead are massive glueball
Glueball

In particle physics, a glueball is a hypothetical composite subatomic particle. It solely consists of gluon particles, without valence quarks. Such a state is possible because gluons carry color charge and experience the strong interaction....
s (these are not widely confirmed experimentally).

Multiplicity of gauge bosons

In a quantize
Quantization

Quantization is the procedure of constraining something from a continuous set of values to a discrete set . Quantization in specific domains is discussed in:...
d gauge theory
Gauge theory

In physics, gauge theory is a quantum field theory where the Lagrangian is invariant under certain transformations.The transformations form a Lie group which is referred to as the symmetry group or the gauge group of the theory....
, gauge bosons are quanta
Quantum

In physics, a quantum is an indivisible entity of a quantity that has the same units as the Planck constant and is related to both energy and momentum of elementary particles of matter and of photons and other bosons....
 of the gauge field
Gauge theory

In physics, gauge theory is a quantum field theory where the Lagrangian is invariant under certain transformations.The transformations form a Lie group which is referred to as the symmetry group or the gauge group of the theory....
s. Consequently, there are as many gauge bosons as there are generators of the gauge field. In quantum electrodynamics
Quantum electrodynamics

Quantum electrodynamics is a relativity theory quantum field theory of electrodynamics. QED was developed by a number of physicists, beginning in the late 1920s....
, the gauge group is U(1); in this simple case, there is only one gauge boson. In quantum chromodynamics
Quantum chromodynamics

Quantum chromodynamics is a theory of the strong interaction , a fundamental force describing the interactions of the quarks and gluons making up hadrons ....
, 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 involving gauge invariance, gauge bosons are described mathematically by field
Field (physics)

In physics, a field is a physical quantity associated to each point of spacetime. A field can be classified as a scalar field, a vector field, or a tensor field, according to whether the value of the field at each point is a scalar , a vector , or, more generally, a tensor, respectively....
 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 interaction has a very short range requires further theoretical insight.

According to the Standard Model
Standard Model

The Standard Model of particle physics is a theory of three of the four known fundamental interactions and the elementary particles that take part in these interactions....
, the W and Z bosons
W and Z bosons

The W and Z bosons are the elementary particles that mediate the weak force. Their discovery has been heralded as a major success for the Standard Model of particle physics....
 gain mass via the Higgs mechanism
Higgs mechanism

In quantum field theory, the Higgs mechanism is a way that the massless gauge bosons in a gauge theory get a mass by interacting with a background Higgs field....
. In the Higgs mechanism, the four gauge bosons (of SU(2)×U(1) symmetry) of the unified electroweak interaction
Electroweak interaction

In particle physics, the electroweak interaction is the unified description of two of the four fundamental interactions of nature: electromagnetism and the weak interaction....
 couple to a Higgs field. This field undergoes spontaneous symmetry breaking
Spontaneous symmetry breaking

In physics, spontaneous symmetry breaking occurs when a system that is symmetry in physics with respect to some symmetry group goes into a vacuum state that is not symmetric....
 due to the shape of its interaction potential. As a result, the universe is permeated by a nonzero Higgs vacuum expectation value
Vacuum expectation value

In quantum field theory the vacuum expectation value of an Operator is its average, expected value in the Vacuum#The quantum-mechanical vacuum....
. 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
Higgs boson

In particle physics, the Higgs boson is a massive Scalar field theory elementary particle predicted to exist by the Standard Model.The Higgs boson is the only Standard Model particle that has not yet been observed....
, which has not yet been observed.

Beyond the Standard Model


Grand unification theories

In grand unified theories (GUTs), additional gauge bosons called X and Y bosons
X and Y bosons

In particle physics, the X and Y bosons are hypothetical elementary particles analogous to the W and Z bosons, but corresponding to a new type of force, such as the forces predicted by grand unified theory....
 would exist. These would direct interactions between quark
Quark

Quarks are a type of elementary particle and major constituents of matter. They are the only particles in the Standard Model to experience all four fundamental interaction, which are also known as fundamental interactions....
s and lepton
Lepton

Leptons are a family of elementary particles, alongside quarks and gauge bosons . Like quarks, leptons are fermions and are subject to the electromagnetic force, the gravitational force, and weak interaction....
s, violating conservation of baryon number
Baryon number

In particle physics, the baryon number is an conservation laws quantum number of a system. It is defined as:whereWhy one third? According to the laws of strong interaction there cannot be any bare color charge, i.e....
 and causing proton decay
Proton decay

In particle physics, proton decay is a Hypothesis form of radioactive decay in which the proton decays into lighter subatomic particles, usually a neutral pion and a positron....
. These bosons would be extremely massive (even more so than the W and Z bosons
W and Z bosons

The W and Z bosons are the elementary particles that mediate the weak force. Their discovery has been heralded as a major success for the Standard Model of particle physics....
) due to symmetry breaking. No evidence of such bosons (for example, due to proton decays seen in Super-Kamiokande
Super-Kamiokande

Super-Kamiokande, or Super-K for short, is a Neutrino detector in the city of Hida, Gifu, Gifu Prefecture, Japan. The observatory was designed to search for proton decay, study solar neutrino and Neutrino#Atmospheric neutrinoss, and keep watch for supernovas in the Milky Way Galaxy....
) has ever been seen.

Gravitons

The fourth fundamental interaction, gravity, may also be carried by a boson, called the graviton
Graviton

In physics, the graviton is a hypothetical elementary particle that mediates the force of gravity in the framework of quantum field theory. If it exists, the graviton must be Mass in special relativity and must have a spin of 2 ....
. In the absence of experimental evidence and a mathematically coherent theory of quantum gravity
Quantum gravity

Quantum gravity is the field of theoretical physics attempting to unify quantum mechanics, which describes three of the Fundamental interaction , with general relativity, the theory of the fourth fundamental force: Gravitation....
, it is unknown whether this would be a gauge boson or not. The role of gauge invariance in general relativity
General relativity

General relativity or the general theory of relativity is the Geometry Theoretical physics of gravitation published by Albert Einstein in 1916....
 is played by a similar symmetry: diffeomorphism invariance.

Z' boson

A Z' boson refers to a hypothetical new neutral gauge boson (named in analogy with the Standard Model
Standard Model

The Standard Model of particle physics is a theory of three of the four known fundamental interactions and the elementary particles that take part in these interactions....
 Z boson).

See also


  • Boson
    Boson

    In particle physics, bosons are subatomic particle which obey Bose-Einstein statistics; they are named after Satyendra Nath Bose and Albert Einstein....
  • Electroweak interaction
    Electroweak interaction

    In particle physics, the electroweak interaction is the unified description of two of the four fundamental interactions of nature: electromagnetism and the weak interaction....
  • Fundamental interaction
    Fundamental interaction

    In physics, a fundamental interaction or fundamental force is a process by which elementary particles interact with each other. An interaction is often described as a field , and is mediated by the exchange of gauge bosons between particles....
  • Quantum chromodynamics
    Quantum chromodynamics

    Quantum chromodynamics is a theory of the strong interaction , a fundamental force describing the interactions of the quarks and gluons making up hadrons ....
  • Quantum electrodynamics
    Quantum electrodynamics

    Quantum electrodynamics is a relativity theory quantum field theory of electrodynamics. QED was developed by a number of physicists, beginning in the late 1920s....


External links

  • by Christopher T. Hill
    Christopher T. Hill

    Christopher T. Hill is a theoretical physicist at the Fermi National Accelerator Laboratory. He did undegraduate work in physics at M.I.T. , and graduate work at Caltech ....