Are Gluons Real Particles or Just Mathematical Constructs?

[Morberticus]

I have been told that the gluon, unlike the photon, is an artefact of the mathematical technique used (perturbation theory), and that the only massless particle in the standard model is the photon.

Is this true?

 

[element4]

It is true that the photon is the only massless gauge boson in the standard model, but the gluon is as physical and not an artifact of perturbation theory. The thing is that the gluon is massive because of the Higgs mechanism (Higgs boson).

 

[Vanadium 50]

The gluon is not massive because of the Higgs boson.

The gluon is massless. However, it does not exist as a free particle.

 

[bcrowell]

The gluon is not massive because of the Higgs boson.

The gluon is massless. However, it does not exist as a free particle.

My knowledge of high-energy physics is virtually nonexistent, so please forgive my ignorance, but I'd be grateful for an answer that uses crayons to the following question.

AFAIK the Higgs mechanism gives mass to the following particles: W+, W-, Z, the Higgs itself, and the quarks. Does it not give mass to the leptons? Why not? What about the neutrinos? Why does it not give mass to other particles in the standard model, such as the gluon?

 

[Parlyne]

My knowledge of high-energy physics is virtually nonexistent, so please forgive my ignorance, but I'd be grateful for an answer that uses crayons to the following question.

AFAIK the Higgs mechanism gives mass to the following particles: W+, W-, Z, the Higgs itself, and the quarks. Does it not give mass to the leptons? Why not? What about the neutrinos? Why does it not give mass to other particles in the standard model, such as the gluon?

Strictly, what one should say is that interactions with the (symmetry breaking) vacuum of the Higgs field gives mass to the W, the Z, the quarks, and the charged leptons. (Whether it is strictly correct to say this about the Higgs boson is complicated by the fact that the Higgs mechanism requires that the Higgs field have a mass term to begin with.) It is unknown whether the mass generation mechanism for neutrinos relies in any way on the Higgs vacuum.

This Higgs does not given mass to the gluon because (as the Higgs carries no color charge) there is no way to write a gauge invariant interaction between the gluon and the Higgs field.

 

[tom.stoer]

It is true that the photon is the only massless gauge boson in the standard model, but the gluon is as physical and not an artifact of perturbation theory. The thing is that the gluon is massive because of the Higgs mechanism (Higgs boson).

As said the gluon doe not get acquire mass due to the Higgs effect.

The gluon does not exist as a free particle that can travel macroscopic distances therefore it is not equally "real" as the photon".

According to the underlying physical theories the gluons is as real as the photon. The defining equations of QED and QCD are structurally similar. The QCD equations are more complicated and seem to rule out the existence of free gluons at low energies relevant for our macroscopic world. But if you could sit on a quark and go round in circles at the LHC both photons and gluons would be equally "real"