# Gauge boson

Gauge bosons, and field quanta are in elementary particle physics, the particles that mediate the fundamental forces. This is done by bosons are emitted from a particle and received from another. Therefore, they are also referred to as exchange particles, messenger particles, carrier particles, force particles or interaction particles.

- 2.1 Grand Unified Theory
- 2.2 gravitational
- 2.3 W ' and Z' bosons
- 2.4 Supersymmetric partners

## Standard Model

One demands of a field theory that their effect should be independent of a local calibration, an additional gauge field may need to be introduced so that the Lagrangian of the theory satisfies this condition. During quantization, so the transition to a quantum field theory, the gauge bosons correspond to the field quanta of the gauge field. Have in common is that they have integer spin, therefore the specification bosons. The spin of all gauge bosons of the standard model has the first amount you are so vector particle.

The photon is the best known gauge boson. It mediates the electromagnetic interaction. The other gauge bosons of the Standard Model are the eight gluons of the strong interaction and the W - and Z bosons of the weak nuclear force.

### Multiplicity

In a quantized gauge theory gauge bosons are quanta of the gauge fields. There are so many gauge bosons as generators of the gauge group. In quantum electrodynamics the gauge group U (1) is one-dimensional, so there is only one gauge boson. The gauge group of quantum chromodynamics, SU (3) has eight generators, accordingly, there are eight gluons. The unified theory of electroweak interactions ( GSW ) is the group SU (2) × U (1) basis, this ultimately leads to the four gauge bosons photon, W -, W - and Z 0 boson.

Gauge bosons are adjoint representations of the underlying symmetry group. For the SU (N ) groups of the standard model, this representation - dimensonal. Therefore, there are 8 gluons and 4 ( = 3 1) gauge bosons of the electroweak theory.

### Mass

The gauge invariance condition requires that all gauge bosons are massless, since a mass term in the Lagrangian is not gauge invariant. The W - and Z bosons, however, have mass. This is an effect of the Higgs mechanism in which the SU (2) × U (1 ) symmetry of the electroweak interaction is spontaneously broken. Be measured not the original SU (2) × U (1) gauge bosons, but linear combinations thereof. The Higgs particle associated is the only experimentally unconfirmed particles of the Standard Model of elementary particle physics. Experimental evidence is a principal object of the Large Hadron Collider (LHC ). On 4 July 2012, the discovery of a boson with a mass of about 125 GeV / c ² was announced by CERN, in which it could be either the Higgs particle.

## Beyond the Standard Model

Many theories beyond the Standard Model of elementary particle physics, introduce new interactions and thus also new gauge bosons. However, to date none of these particles was measured in one experiment. In fact, even the graviton is a hypothetical particle, since no quantum gravity theory has been confirmed by experiments.

### Grand Unified Theory

In Grand Unified Theories ( GUTs ) predict additional gauge bosons as X and Y. This would convey interactions between quarks and leptons, so that the conservation of baryon number violating and could thus cause a proton decay. These bosons would by symmetry breaking extremely massive ( even heavier than the W and Z bosons ), their spins 0 or 1

### Gravity

The gravitational interaction is not an object of the standard model, as well as the hypothetical carrier, the graviton in contrast to the other. This is also why an exception because it is a Tensorboson as a spin- 2 particles, which is in agreement with the attractive interaction between masses (called " gravitational charge ").

### W ' and Z' bosons

W 'and Z' (read: W -prime and Z prime ) are hypothetical gauge bosons, the virtue of the fermions of the standard model coupled to their isospin. Your spin is 1

By extending the standard model to include at least one additional U (1) gauge group a Z ' boson can be produced, but no W' boson. Another way of enlargement, n SU (2 ) gauge groups to adopt, one of which produces the usual W and Z bosons, the other n - 1, the W ' and Z' bosons.

### Supersymmetric partners

The hypothetical supersymmetric partners of gauge fields are the following gaugino fields:

- Eight gluinos as superpartners of the gluons.
- The electroweak gaugino fields mix after the minimal supersymmetric standard model ( MSSM ) with the Higgsino fields to two pairs of electrically charged charginos and four electrically neutral neutralino hypothetically observable particles. The Higgsinos are the superpartners of the hypothetical Higgs fields, of which there are others in the MSSM.
- A gravitino as the supersymmetric partner of the graviton on the theory of supergravity ( SUGRA ) - as the graviton is not a part of the SM not part of the MSSM.