I Why are gluons considered to be elementary particles?

[Sophrosyne]

Gluons are often depicted as fundamental particles in the Standard Model. But in looking at their mechanism, it seems they are not really fundamental particles in the sense that they are fundamental, indivisible, building blocks. They are mesons- a composite quark-antiquark pair, where their spin adds up to zero and therefore they act as gauge bosons.

And speaking of that, it seems even the weak force, the W bosons, can also be depicted equivalently as mesons, can't they?

Am I misunderstanding this somehow?

 

[mfb]

They are mesons- a composite quark-antiquark pair

They are not. Mesons have mass, mesons are color-neutral, mesons have excited states, and various other properties that differ from gluons.

And speaking of that, it seems even the weak force, the W bosons, can also be depicted equivalently as mesons, can't they?

It cannot.

 

[ChrisVer]

They are mesons- a composite quark-antiquark pair, where their spin adds up to zero and therefore they act as gauge bosons.

where did you get that information?
The Standard Model particles are the following:
Vector Bosons (Spin=1) : W/Z-bosons [W/Z], photons [γ], gluons [g]
Scalar Boson (Spin = 0) : Higgs [H]
Fermions (Spin=1/2):
__leptons don't interact via strong interactions:
electron (e), muon (μ), tau (τ) and the respective neutrinos (ν_e,μ,τ)
__quarks do interact via strong interactions:
up (u), down (d), charm (c), strange (s) , top (t) , bottom (b)

 

[Sophrosyne]

I see. I guess I was seeing the use of mesons as force carriers for the inter-hadron interactions, and I also saw that gluons carry color charge in eight different types even for the inter-quark interactions, represented by the "color octet" states. These are represented in a quark-antiquark representation, and thought that was the same thing as a meson. But that just seems to be the quantum state of the gluon, not a meson.

 

[Orodruin]

The quark-antiquark colour representation is a 9-dimensional representation (since it is the product of two 3-dimensional ones). It can be split into a colour singlet, which is the colourless trivial representation of mesons, and a colour octet - the same representation that the gluons transform according to.