What would a hypothetical quark-quark collision yield?

[Auxirius]

TL;DR Summary

I understand that individual quarks are incredibly hard if not impossible to have 'exist' in places like particle accelerators since they will usually undergo hydronization from the products of the collision. However, say that hypothetically, we are able to keep hydronization from occurring, and are somehow able to make two or three quarks collide. What would happen?

As seen in the summary, my question is purely hypothetical and I understand that it would most likely be impossible to happen (or I just haven't read enough). The concept that quarks and leptons are the fundamental particles of the universe has existed for a while now - therefore we know that they are what makes up particles like neutrons and protons that make up nuclei of atoms, etc.

Given that this concept hasn't been 'broken' yet, I suppose it is believable that quarks and leptons cannot be made up of anything further - they are quite literally THE fundamental particles. So as I was thinking about these concepts, I thought 'What would occur during a quark on quark collision in an accelerator, similar to particle collisions in particle accelerators with particles like protons?'

Again, as explained in the summary, I understand that hadronization tends to occur practically instantly for the products of subatomic particle collisions, so executing an experiment like this would be incredibly hard. However, say we somehow can do this experiment. What would happen?

I have a general idea of what could happen but it may be a rather stupid one.
In order to make sure we form a baryon (since they're stabler than mesons), we'd collide 3 quarks in total. Say we try to form a proton, 2 ups and 1 down quark. For the sake of this hypothetical experiment, say we have a singular point in the accelerator where we can collide all three at the same time, with a high energy from acceleration. I almost want to say that we could see some form of hadronisation occurring - where all of the quarks would try to join together and form a singular subatomic particle (our proton). However, my issue with this idea is where the gluons come from and where the energy goes?

Obviously gluons are a very hard thing to 'detect', they were, after all, found with the three-jet-event idea from electron-positron annihilation, and even then gluons aren't something we can see because they are a boson, and hence massless. So I suppose this poses another question - where do gluons occur? We know they are the mediators of the strong force between quarks but could they exist by themselves in a sense? Is there a place where they come from or are formed? Could gluons somehow tie in with forces of collisions? Also, during the three-quark collision, what would happen to the Kinetic Energy? I remember reading something that the quarks and gluons within protons all contribute to the total momentum of the proton itself, which is how we had the first circumstantial evidence for the existence of gluons in protons. Would this occur here, where all of the Kinetic Energy of said quarks 'merge' into a total Kinetic energy for the proton?

I know this is a lengthy thread and I probably said some things which are outright wrong, which I do apologise for as I am not an expert on this field and only know certain principles and rules. I suppose in the very end, this all whittles down to 2 or 3 questions:

Can a three-quark-collision cause hadronisation?
If yes, where do the gluons come from?
What would happen to the Kinetic Energy? Would it all sum up to be the Kinetic Energy of the new particle?

Thank you in advance for any replies.

 

[Orodruin]

Summary:: I understand that individual quarks are incredibly hard if not impossible to have 'exist' in places like particle accelerators since they will usually undergo hydronization from the products of the collision. However, say that hypothetically, we are able to keep hydronization from occurring, and are somehow able to make two or three quarks collide. What would happen?

What would occur during a quark on quark collision in an accelerator, similar to particle collisions in particle accelerators with particles like protons?

Proton collisions at high energy (such as at the LHC) are effectively collisions of individual partons due to the asymptotic freedom of the strong interactions.

 

[ohwilleke]

Can a three-quark-collision cause hadronisation?

First off, quark-quark annihilation is not a thing, but quark-antiquark annihilation is a thing.

Second, three point connections are considered in Standard Model calculations using Feynman diagrams. They are considered possibilities that are factored into the probabilities of particular end results which is the result of every conceivable way something can happen including indirect and goofy ways as well as straightforward and obvious ways.

Third, quarks form hadrons because their gluon fields bind them to each other, not because they actually collide. So hadrons and three point collisions don't have anything to do with each other.

When it comes time to make hadrons, quarks basically just don't touch each other. They just trade gluons (and if you need to get really precise, also photons and weak force bosons) with each other. A "contact-like" annihilation interaction causes a hadron to cease to be.

If yes, where do the gluons come from?

At a nuts and bolts level, fundamental particles that have strong force color charge (i.e. quarks and gluons) have a probability of emitting gluons and a probability of absorbing gluons. These probabilities are identical and are quantified by the strong force coupling constant that is usually called α_s (i.e. alpha with subscript s for the strong force), which has a dimensionless value of about 0.118 at the energy scale of the W boson mass.

This is perfectly analogous (except for the fact that electromagnetic charges come in only positive and negative, while there are three kinds of quark color charges, three kinds of antiquark color charges and eight kinds of gluon color charges), to the way that a charged particle like the electron has a probability of emitting or absorbing a photon, which is quantified by the electromagnetic coupling constant, usually reported as the "fine coupling constant" and denoted with the symbol α_EM in the limit of a zero energy scale, which is a dimensionless number of about 1/137 and has a value at the comparable energy scale of the W boson mass that I used before of about 1/125 (i.e. much smaller, which is why we call the strong force the strong force).

What would happen to the Kinetic Energy? Would it all sum up to be the Kinetic Energy of the new particle?

The rule is that mass-energy is conserved.

To every so slightly oversimplify, you figure out the mass of all of the particles you start with and convert them to energy with E=mc², then you figure out the mass of all of the particles that you end with and convert those to energy. Then, you figure out the difference.

For any given kind of fundamental particle, the mass-energy of that particle is always identical. They are interchangeable in that respect. So, you can just work it out one and put it in a table for each particle, if you want to.

If the ending particles have less mass than the particles you start with, the difference gets converted into energy, generally speaking, kinetic energy. If the ending particles have more mass than the particles you start with, the difference is, generally speaking, sucked out of the kinetic energy and turned into mass.

It is a bit trickier than that because mass-energy isn't the only thing you have to conserve when you are looking at what is possible. You have to conserve electromagnetic charge. You have to conserve color charge. You have to conserve baryon number. You have to conserve lepton number. You have to conserve linear momentum. You have to conserve angular momentum. There is a lot of accounting involve that limits the range of possibilities.

It is also a bit tricky because the mass-energy at the beginning needs to equal the mass-energy at the end, but in between Nature allows us to "borrow" mass-energy for an intermediate step, so long as we return it when we're done in a final state (subject to rules that make bigger borrowings less probable than smaller ones). When we employ this little "cheat" that Nature actually allows under its own house rules, we call the intermediate particles that violate mass-energy conservation but never become observable because we only observe the beginning and the end of the process "virtual particles."

 

[artis]

It is a bit trickier than that because mass-energy isn't the only thing you have to conserve when you are looking at what is possible. You have to conserve electromagnetic charge. You have to conserve color charge. You have to conserve baryon number. You have to conserve lepton number. You have to conserve linear momentum. You have to conserve angular momentum. There is a lot of accounting involve that limits the range of possibilities.

It is also a bit tricky because the mass-energy at the beginning needs to equal the mass-energy at the end, but in between Nature allows us to "borrow" mass-energy for an intermediate step, so long as we return it when we're done in a final state (subject to rules that make bigger borrowings less probable than smaller ones). When we employ this little "cheat" that Nature actually allows under its own house rules, we call the intermediate particles that violate mass-energy conservation but never become observable because we only observe the beginning and the end of the process "virtual particles."

The way this is written simply seems like the atomic scale version of IRS tax reform - "add this, subtract that , and God forbid you forget to account for something in the end!"
Nuclear bookkeeping is what it is.
Overall I salute you @ohwilleke for making it sound so interesting.


Speaking of this

When we employ this little "cheat" that Nature actually allows under its own house rules, we call the intermediate particles that violate mass-energy conservation but never become observable because we only observe the beginning and the end of the process "virtual particles."

Hmm , so virtual photons forming Coulomb charge for charged particles like protons and making up a static E field are also constantly violating mass-energy? Or is this the same reason why single electrons for example cannot exist as they would radiate away energy and they only acquire charge once another electron is present as then they can exchange virtual photons, so the middle step is "borrowed energy" but the end and beginning is fine, anyway please elaborate.

 

[ohwilleke]

The way this is written simply seems like the atomic scale version of IRS tax reform - "add this, subtract that , and God forbid you forget to account for something in the end!"
Nuclear bookkeeping is what it is.
Overall I salute you @ohwilleke for making it sound so interesting.

What can I say? Many days each month I'm a tax lawyer. What could be more interesting that accounting?

Speaking of this

Hmm , so virtual photons forming Coulomb charge for charged particles like protons and making up a static E field are also constantly violating mass-energy?

No. When a particle emits a photon it loses a little energy. When a particle absorbs a photon it gains a little energy. Particles are usually immersed in a photon sea and migrate towards points of equilibrium.

When you have out of equilibrium exchanges of photons you get motion. Scale this up enough, and this is why, for example, you can use electric power to make a Tesla sedan zip down the road.

Or is this the same reason why single electrons for example cannot exist as they would radiate away energy and they only acquire charge once another electron is present as then they can exchange virtual photons, so the middle step is "borrowed energy" but the end and beginning is fine, anyway please elaborate.

Single electrons can and do exist and are stable. You are misinformed.