What Happens to Very Energetic Protons After Collision?

[Sphere]

Hello, i was wondering, during the pair creation caused by the collision between a very energetic proton and a target (atomic nucleus) in a particle accelerator, what happens to the very energetic proton after the collision? Is it destroyed, intact, split into quarks or something else?

Thank you!

 

[Vanadium 50]

Is it destroyed, intact, split into quarks or something else?

Any of these can happen.

 

[malawi_glenn]

The pair creation of what?

 

[Vanadium 50]

Does it really matter?

 

[mfb]

Any of these (pairs) can happen with sufficient energy.

 

[malawi_glenn]

Does it really matter?

still leaves my sleepless at night, not knowing what pair was created :(

 

[Sphere]

So, if I understand correctly, depending on the speed at which the proton strikes the target and therefore on the type of pair of particles created, one of these situations can occur (intact, destroyed, split into quarks).

For a proton-antiproton pair created by the collision of a very energetic proton with a target, what would happen to the energetic proton after the collision?

 

[malawi_glenn]

Who said it depends on the speed? It is quantum mechanics so there is cross sections involved. Also it depends on the interaction, was it electromagnetic or strong force involved?

But yes, now we have an example of a process and an interaction $p + p \to p + p + p + \bar{p}$

Protons are identical particles, how are you going to label them?

 

[mfb]

At low energies (few GeV) $p + p \to p + p + p + \bar{p}$ is the most likely reaction that produces an antiproton. Go to higher energies and you get tons of different reactions with relevant probabilities.

 

[snorkack]

Any of these can happen.

Is "split into quarks" a realistic option?
The target was specified as "nucleus". Is "captured into a nucleus" one of the options?

 

[PeroK]

So, if I understand correctly, depending on the speed at which the proton strikes the target and therefore on the type of pair of particles created, one of these situations can occur (intact, destroyed, split into quarks).

For a proton-antiproton pair created by the collision of a very energetic proton with a target, what would happen to the energetic proton after the collision?

What QM tells you is the possible outcomes and the probability of measuring each outcome of an interaction -in this case an interaction between two protons. There's no sense in which you can say what happens to the original particles, other than they took part in the interaction.

A proton is a bound state of three quarks, and (as others have pointed out) there is no way to label a proton with a serial number. Practically and theoretically, therefore, all protons are indistinguishable and all you can say is that two protons interacted and three protons and an antiproton were the result of that interaction. In particular, you cannot identify the original protons with two of the resulting three and say in any meaningful way which proton was created.

In that sense, you are thinking too classically rather than quantum mechanically about pair production.

 

[snorkack]

At low energies (few GeV) $p + p \to p + p + p + \bar{p}$ is the most likely reaction that produces an antiproton. Go to higher energies and you get tons of different reactions with relevant probabilities.

Already in "few GeV"
You already will have a reaction with at least slightly lower threshold:
$p + d \to 3-He + p + \bar{p}$
Low cross-section, probably.
And what precisely is a pair?
Higher energies, but still a few GeV, and you will have plenty of reactions like
p = n+π⁺
That is one obvious way to "destroy" any, or possibly all, protons involved - have a reaction whose inputs include protons but outputs neither include not contain protons.

 

[Vanadium 50]

Please don't hijack this thread. Especially with misinformation.

Yes, kinematically, p + bowling ball → p + bowling ball + p + pbar has a lower threshold than p + p → 3 p + pbar. And my cart's name is Mittens. Both are facts, and neither fact is relevant to the OP's question.

Further, using large nuclear targets doesn't actually help in real life. The proton beam energy is several GeV, and nuclear binding per nucleon is a few MeV per nucleon (for the deuteron it's 1.1). The system does not look like a single body to the proton - it looks like multiple nuceons close together. Further, the wavelength of a proton at these energies is smaller than a proton: again, the system does not look like a single body to the proton - it looks like multiple nuceons close together. (indeed, some proton structure will start to be visible)

I don't want to get into an endless loop of arguing "this doesn't happen" "yeahbut it could!" "but it doesn't" "how about once in a trillion attempts?" and would hope that this diversion can be put behind us.

 

[snorkack]

Which of the outcomes would you classify as "split into quarks" in a meaningful sense? Quark confinement holds at all known energy scales and is reasonably expected to apply at the unknown scales, too.

 

[Vanadium 50]

Which of the outcomes would you classify as "split into quarks"

Production of jets, which arise from a quark ejected from the system.

 

[artis]

There's no sense in which you can say what happens to the original particles, other than they took part in the interaction.

A proton is a bound state of three quarks, and (as others have pointed out) there is no way to label a proton with a serial number.

So the mentioned case where the proton is preserved as intact, how would one know this based on that we can't differentiate between individual like particles?
Only by their energy?

So that would be in the case of scattering both elastic and inelastic?

 

[Drakkith]

So the mentioned case where the proton is preserved as intact, how would one know this based on that we can't differentiate between individual like particles?
Only by their energy?

If you're talking about high-energy collisions where you start with a proton and end up with many other particles including a proton, then you don't really know what happened to the original proton at all. All you know is that a proton and some energy went into an interaction and out of that interaction comes a proton with some energy and some other stuff.