What happens to free quarks in particle accelerators?


by Uchuujin_7
Tags: accelerators, free, particle, quarks
Uchuujin_7
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#1
Jun7-05, 01:04 PM
P: 4
I'm new to quantium physics but taking an interesting and trying to read more every day.

I have a bit of a silly questions - in particle accelerators when collisions with protons or neutrons free quarks, what is the ultimate fate of the free quarks? It's my understanding that a quark isn't content to just exist alone and there isn't really an abundance of free quarks for it to join with. Does it decay into other elementry particles like photons?
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James Jackson
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#2
Jun7-05, 01:41 PM
P: 166
They undergo a process termed hadronisation. Basically, you're not going to get a singular quark produced, as this would defy basic conservation laws. If we look at a general case where a quark and an anti-quark pair are moving away from each other (in the center of mass frame), due to the strong force increasing with distance, a potential exists between the pair of quarks. We can think of this 'flux tube' as consisting of lots of gluons. When the potential energy of the flux tube (gained from the kinetic energy of the moving particles) is great enough to create another pair of particles, this happens, the orginal quark pairing up with an antiquark, and the original antiquark pairing up with a quark.

This is a simplified description, but I hope it makes sense.
Uchuujin_7
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#3
Jun7-05, 02:04 PM
P: 4
Thanks for the answer. What you are saying makes some sense to me.

When particles collide and free quarks go flying - are they quarks from the anti-/protons or neutrons that collided, or were they created in the energies of the collision?

One of the reasons I'm asking about this is I recently saw some bubble chamber images then went and read about how old bubble chambers worked and I realized that the particles tended to leave a trail and vanish at some point (when their energies decreased enough to not leave a trail anymore.) I wondered what became of them at this point.

Bubble chambers are old though, I'm not sure if at that time they were working with energies high enough for quarks or what the particles were creating the bubble trails.

James Jackson
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#4
Jun7-05, 06:16 PM
P: 166

What happens to free quarks in particle accelerators?


When you talk about particle collisions creating quarks that's completely different to neutron research...

Anyway, the quarks which then hadronise and whose products we see are created 'out of' the energy from the initial matter-antimatter collisions.

Coming to your bubble chamber question, all hadrons are made of quarks, so when we look at tracks due to hadrons interacting / decaying we are looking at particles made of quarks. i.e. http://rd11.web.cern.ch/RD11/rkb/PH14pp/node17.html Shows 8 incoming particles (K mesons), one of which strikes a proton and decays, as can be seen by the branching of the tracks in a number of places.

You are made of up and down quarks, just because you're not accelerated to speeds close to the speed of light doesn't mean there aren't quarks there...

When particles stop leaving a trail, that doesn't mean stuff still isn't going to happen to them. Particles will continue to decay until they reach a final stable state; just about everything ends up as photons (most things decay to pions, which then usually decay to photon pairs).

What you should realise is that there is no such thing as a realisable free quark - they've never been observed at the energies we can produce.
Haelfix
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#5
Jun8-05, 09:58 PM
Sci Advisor
P: 1,663
Not to mention fundamentally experimentally impossible. They would react with nuclei in the detector/vacuum long before it could be ever detected, even if you could wrench them apart for long enough (say with a Planckian accelerator the size of our galaxy).
James Jackson
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#6
Jun11-05, 09:08 AM
P: 166
Quote Quote by Haelfix
(say with a Planckian accelerator the size of our galaxy).
Now that is an accelerator I'd like to see...


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