Do Alternative Explanations for Gluons Exist and How Can We Test Them?

[Cody Livengood]

TL;DR Summary

I understand how the existence of quarks is inferred from the three particle-emitting cones or jets and by the quarks’ ability to deflect particles passing through the composite particle, but I don’t see how the existence of gluons is conclusively demonstrated by this rather than just being an interpretation of the observation.

I understand how the existence of quarks is inferred from the three particle-emitting cones or jets and by the quarks’ ability to deflect particles passing through the composite particle, but I don’t see how the existence of gluons is conclusively demonstrated by this rather than just being an interpretation of the observation. How do we know that two of the jets were produced by quark-antiquark pairs that fragmented into hadrons and the third was produced by a gluon that fragmented into hadrons? How can we tell the difference?

 

[malawi_glenn]

It fit the preductions of the QCD model, in which there are gluons.

The existence of all subatomic particle are "interpolation of the observation"

Same as say the Higgs boson, we think it exists due to the observation matches the models prediction to a very high statistical certainty.

 

[vanhees71]

https://home.cern/news/news/physics... 1979,particles known collectively as hadrons.

 

[Cody Livengood]

https://home.cern/news/news/physics/four-decades-gluons#:~:text=Forty years ago, in 1979,particles known collectively as hadrons.

I already read that article, but I'm not sure it really answers the question I asked.

 

[Cody Livengood]

It fit the preductions of the QCD model, in which there are gluons.

The existence of all subatomic particle are "interpolation of the observation"

Same as say the Higgs boson, we think it exists due to the observation matches the models prediction to a very high statistical certainty.

Sooo... you're saying that we don't have any actual proof that gluons exist?

 

[Vanadium 50]

If there were no gluon, the number of events that look like the following is roughly zero.

 

[Cody Livengood]

If there were no gluon, the number of events tghat look like the following is roughly zero.

View attachment 312756

I thought that experiment was used to verify the existence of quarks. The explanation is that two of the jets were produced by quark-antiquark pairs that fragmented into hadrons. I don't see how we know that one of them was caused by a gluon.

 

[malawi_glenn]

Sooo... you're saying that we don't have any actual proof that gluons exist?

What is an actual proof?
Think about it for a while.
Do we prove things in natural sciences?

 

[Cody Livengood]

What is an actual proof?
Think about it for a while.

I suppose it would be an observation that we, for the time being, have no other explanation for. That still doesn't really answer my question though. I'm not asking this for fun. I'm working on a serious project. If we have no real reason to believe that they exist other than "it fits the theory," then it's okay to say so.

 

[Dale]

I suppose it would be an observation that we, for the time being, have no other explanation for. That still doesn't really answer my question though. I'm not asking this for fun. I'm working on a serious project. If we have no real reason to believe that they exist other than "it fits the theory," then it's okay to say so.

Of course it is ok to say so, that is the only reason we ever have to believe anything in science. That is how the scientific method works.

Did you think that science ever let's us know something in a different way?

 

[Cody Livengood]

Of course it is ok to say so, that is the only reason we ever have to believe anything in science. That is how the scientific method works.

Did you think that science ever let's us know something in a different way?

*rolls eyes* I think you're taking my statement a little too far and ignoring the actual question at hand. Not helping.

 

[Ibix]

I suppose it would be an observation that we, for the time being, have no other explanation for.

Then see #6.

*rolls eyes* I think you're taking my statement a little too far and ignoring the actual question at hand. Not helping.

Actually, the problem is that you don't seem to be making clear what you want. If you wanted "an observation that we, for the time being, have no other explanation for" then there's already one in post #6. If you want something that couldn't possibly be anything other than a gluon then you have a fundamental misunderstanding of how science works. If you want something else, what do you want?

 

[Cody Livengood]

Then see #6.

Actually, the problem is that you don't seem to be making clear what you want. If you wanted "an observation that we, for the time being, have no other explanation for" then there's already one in post #6. If you want something that couldn't possibly be anything other than a gluon then you have a fundamental misunderstanding of how science works. If you want something else, what do you want?

I want to know how we know it was produced by a gluon and not the third quark in the nucleus or by three quantum vortexes linked in a ring or anything else. What's the proof?

 

[vanhees71]

I thought that experiment was used to verify the existence of quarks. The explanation is that two of the jets were produced by quark-antiquark pairs that fragmented into hadrons. I don't see how we know that one of them was caused by a gluon.

No, the three-jet events are clear indications for gluons!

 

[Ibix]

I want to know how we know it was produced by a gluon and not the third quark in the nucleus or by three quantum vortexes linked in a ring or anything else. What's the proof?

Come up with a detailed mathematical model of how those operate and make predictions for ratios of different collision products based on that model. If those don't match experiment then it's not a possibility. If they do match experiment it's a possibility, and we'd have to find some prediction your model makes that differs from the standard model and try that experiment.

Models that include gluons currently predict experimental outcomes as precisely as we can measure, and no other model does (as far as I'm aware). But all knowledge is subject to revision if new evidence not matching current models comes along.

 

[malawi_glenn]

That still doesn't really answer my question though

It does, the cross section (probability) of 3, 4, 5, ..jet events is best explained by the model of QCD.

There are also processes whos cross sections that depends on the gluon parton distribution functions, which fit the model of QCD more or less perfectly.

No, the three-jet events are clear indications for gluons!

It is not only their existence, but also the rate of which 3-jet events are produced in comparison with 2 jet events.

Gluon is a spin one particle, so you get a certain angle distribution of the jets, which you can measure and compare with data. This is of course also been done.

I want to know how we know it was produced by a gluon and not the third quark in the nucleus or by three quantum vortexes linked in a ring or anything else. What's the proof?

There are no proofs in natural sciences.

But in a positron-electron collision, where is the "third quark in the nucleus"?
In order to undestand why the three jet events from electron-positron collisions, you need to know something about the models available to explain the experimental outcome.
And, it turns out that QCD is the model that BY FAR, explains all that data which has to do with hadron jets.

Quantum vorticies? I thought you were studying particle physics and not condensed matter physics?

I understand that this is some kind of school project for you.
Could you mention the name of the course, what level it is and syllabus, perhaps also the instructions for the project?

 

[Drakkith]

I want to know how we know it was produced by a gluon and not the third quark in the nucleus or by three quantum vortexes linked in a ring or anything else. What's the proof?

There is no proof. There is only evidence that supports or doesn't support the framework, model, or theory that you're using. In this case the evidence supports the idea that the tracks originate from the decay of a gluon and not something else.

 

[Dale]

*rolls eyes* I think you're taking my statement a little too far and ignoring the actual question at hand. Not helping.

It does help. The issue isn't the evidence for gluons, the issue is that you don't understand how the scientific method works.

I understand how the existence of quarks is inferred from the three particle-emitting cones or jets and by the quarks’ ability to deflect particles passing through the composite particle, but I don’t see how the existence of gluons is conclusively demonstrated by this rather than just being an interpretation of the observation.

Sooo... you're saying that we don't have any actual proof that gluons exist?

The standard that you are rejecting here is the same standard by which we know anything scientifically. Insofar as you reject this evidence as "actual proof" then there is no such thing as "actual proof" anywhere in science.

As a refresher, in science we ideally start with a theory. From that theory we make a prediction about the outcome of an experiment we could run, this prediction is called a hypothesis. We then run the experiment and compare the actual observation to the hypothesis. If the observation is consistent with the hypothesis then we interpret that as being experimental validation of the theory. That is simply how science works.

So, the question is, why do you think that a different standard of scientific evidence should apply for gluons? Or equivalently why do you think that the usual scientific method should not apply to gluons?

 

[malawi_glenn]

One should also note that the QCD model can explain and predict a pletora of phenomena.
If one model can explain and predict 50 different things, or if you need 50 models to explain those things. The "one" model is preferred.

 

[Cody Livengood]

There is no proof. There is only evidence that supports or doesn't support the framework, model, or theory that you're using. In this case the evidence supports the idea that the tracks originate from the decay of a gluon and not something else.

How so? How does it support that idea? I could say that it supports the idea that it was produced by three quantum vortexes linked in a ring or that the three jets were produced just by the three quarks and I could say that the experiment "supports the idea." Where is the proof (or whatever you want to call it) that it was produced by gluons?

 

[malawi_glenn]

I could say that it supports the idea that it was produced by three quantum vortexes linked in a ring or that the three jets were produced just by the three quarks and I could say that the experiment "supports the idea." Where is the proof (or whatever you want to call it) that it was produced by gluons?

you need to do the calculations.

It is quite an easy task to calculate the cross section and angular distribution of $e^+ + e^- \to jjj$
We did that in my first QFT course, it was a problem in Peskin and Schroeder QFT book

Physical models are mathematical models, you can not just mash fancy words together, you have to do the calculations. You should know this is if you are taking a physics class.

 

[Motore]

I could say that it supports the idea that it was produced by three quantum vortexes linked in a ring or that the three jets were produced just by the three quarks and I could say that the experiment "supports the idea."

Then you can show us the calculations using this theory you are proposing and also show that they match the observational data.

 

[malawi_glenn]

Then you can show us the calculations using this theory you are proposing and also show that they match the observational data.

And predict other, not yet observed, phenomena, so that the theory is falsifiable.
in other words, the scientific method.

 

[Cody Livengood]

you need to do the calculations.

It is quite an easy task to calculate the cross section and angular distribution of $e^+ + e^- \to jjj$

Physical models are mathematical models, you can not just mash fancy words together.

Could you translate into words what the proof is? Explain the evidence using words that actually mean something physical, like "Because two of the jets went straight and the third spiraled" or something like that. Otherwise, I still don't see the observation as proof for one model rather than another.

 

[malawi_glenn]

Could you translate into words what the proof is?

The language of physics is math.

 

[Ibix]

Where is the proof (or whatever you want to call it) that it was produced by gluons?

See @malawi_glenn's post #16. Basically, if we posit gluons then the maths describing them leads to accurate predictions of particle collisions. If you want to posit something else you need to come up with maths describing that something else and show that it makes the same predictions.

Note that the key thing here is the maths. The words are more or less irrelevant. So just saying "quantum vortexes did it" is useless without a mathematical description of what quantum vortexes are and how they interact to produce the observed collision products.

We do not have any mathematical models that make correct predictions and do not include gluons.

 

[Ibix]

Could you translate into words what the proof is?

Not really. That's why we use maths for the job.

Again, the reason we believe gluons exist is the same reason we believe anything exists: mathematical models including them make accurate predictions.

 

[Cody Livengood]

Not really. That's why we use maths for the job.

Again, the reason we believe gluons exist is the same reason we believe anything exists: mathematical models including them make accurate predictions.

That's honestly not good enough for me. I want to understand what is physically going on.

 

[malawi_glenn]

That's honestly not good enough for me.

Well learn Quantum Field Theory then.

 

[berkeman]

Thread closed temporarily for Moderation...

 

[berkeman]

After some Moderation chores, the thread is reopened.

 

[Motore]

That's honestly not good enough for me. I want to understand what is physically going on.

Start with these:
https://arxiv.org/pdf/1012.2288.pdf
https://arxiv.org/pdf/1501.04794.pdf
https://pdg.lbl.gov/2011/reviews/rpp2011-rev-qcd.pdf

Then come back with the acquired knowledge and let us know what you don't understand or it's hard for you to grasp.

 

[Ibix]

That's honestly not good enough for me. I want to understand what is physically going on.

Then you need to learn enough maths to understand QFT. Please don't confuse "I personally don't understand the models" with "the models don't explain anything".

All physical models are mathematical. It should be unsurprising that language developed for one ape to be able to tell another ape where the tasty fruit is doesn't really cut it for describing the basic structure of the universe. We use maths to describe physics because it seems to be the best tool for the job.

You may also need to read a bit on positivism, since "all knowledge is conditional, and people use the models that best predict reality" seems to have come as a nasty shock to you.

Posting this because I wrote it before the thread closure and it was still in draft. I think I've said all I'm going to say on this topic.

 

[Dale]

We do not have any mathematical models that make correct predictions and do not include gluons.

This is really the bottom line.

@Cody Livengood I think that you still need to look into your own understanding of science. You are already aware of the evidence. But for some reason you want to hold this specific piece of evidence to a different standard. To me, that indicates that you have a problem with the scientific method, or you have some difficulty applying it consistently.

 

[PeterDonis]

I could say that it supports the idea that it was produced by three quantum vortexes linked in a ring or that the three jets were produced just by the three quarks and I could say that the experiment "supports the idea."

No, you can't just say these things. You have to demonstrate these things, by showing your theoretical model and calculating what it predicts. That's what the scientists who developed QCD have done. They didn't just "say" that the experiments show gluon events. They calculated, in numerical detail to many decimal places, the exact predictions of their model and compared them with the experimental results. All of this has been in published peer-reviewed papers for decades, and in textbooks for almost as long. It's accessible to anyone who is willing to do the work of reading and understanding. Either you are willing to do that work, or you aren't. And if you aren't, then asking for an "explanation" is simply out of line; it's like a person who says they want to be a concert pianist, but who doesn't want to practice. There are no shortcuts.