Cody Livengood said:
I'm one class away from being halfway done with my physics degree
Must be a very good university that teaches QFT already then (usually a year 4 course) and is failing misarable at explaining the scientific method and not making their students threw out their own non-scientific theories.
Anyway
vanhees71 said:
The "running coupling" of QCD can be measured and agrees pretty well with the predictions of the theory:
https://pdg.lbl.gov/2022/web/viewer.html?file=../reviews/rpp2022-rev-qcd.pdf#chapter.9
You should read chapter 9.4
Dale said:
the main experimental observation that leads us to believe that the color force grows with distance is the absence of free quarks.
and results from deep inelastic scattering, showing that at high energy scales (small distances), quarks are basically free particles. So combing these two results, we can infer that the strength of the interaction between quarks goes like this
(from that PDG article)
Running of coupling constant is a general QFT phenomena, that the strength of the interaction varies with distance (energy scale) is not only for QCD.
For the electromagnetic force (QED), the behaviour is different. There the strength of the interaction becomes larger and larger for smaller distances (higher energy scales) and weaker at larger distances (Coulombs law). Are you familiar with electric screening of the nuclei in atomic physics? In an atom, the electrons in the outer "shells" is subjected to a weaker electric force than the inner shell electrons. Not only because they are farther out, but also because the inner electrons are "screening" the electric charge of the nucleus.
Here is an heuristic analogy of that in QFTs. All particles are surronded by a "cloud" of virtual particles, which in some sense is working like the electron shells around a nuclei in an atom. At higher energies (shorter distances) you get closer to the "real" particle. For QCD, it actually turns out that because the gluons can interact with themselves (and the fact that there are just the right amount of quarks, the formula can be found here
https://en.wikipedia.org/wiki/Beta_function_(physics) ) the sign of this screening effect is opposite that of QED.
Of course, what I wrote above are just fancy words. One have to do the actual QFT calculations. And a result of such calculations is that coupling constants vary with the energy scale of the interaction (Nobel prize 2004). You mentioned that you were quite familiar with QFT in another thread, so it should be within your reach to perform and understand such calculations yourself.
What one does experimentally is to observe and measure the rate of certain events, like number of jets. Then you compare the experimentally measured rate with what your model would yield as a theoretical rate with
a) constant interaction strength and
b) varying interaction strength .
And it turns out that a) sucks at explaining data and that b) is what describe data best. Furthermore, if you insert precisely the energy scale dependence of the interaction strength as it is
predicted by QCD, you get an
extremely good fit. Now there are of course some subtleties here, otherwise it would not require hundreds of particle physicists with a phd to make these experiements and calculations (though the basics are accesible to master students). But roughly speaking, this is what you do, i.e. the scientific method.
