Can quarks be separated from a proton/neutron?

[P. Brien]

As we know that a proton and a neutron is comes from an interaction of three quarks that inside of it. I think about
1. "Can we separated them from a proton or a neutron?"
2. "What will be happen if we can do that?"
3. "Is it will result a big explosion like nuclear fusion/fission?"

 

[tom.stoer]

Regarding 1: due to confinement this is impossible at low energies; think about two quarks bound by a string of gluons; seperating the quarks will eventualy break the string with new quark - antiquark pairs (= e.g. pions); you will never see free quarks; at high energies (and pressure) it is possible to dissolve protons and neutrons completely; this is called quarks-gluon-plasma but again you don't see individual quarks.

 

[phyzguy]

One simple way to think of it is the following. Suppose you try to pull one of the u quarks out of a proton. The strong force is so strong that as the distance between the u quark and the other two (u and d) quarks increases, the amount of energy you have to put in increases rapidly. It quickly becomes energetically more favorable to create a new quark-antiquark pair out of the vacuum than to increase the distance further. So this is what happens - a pair (say u - ubar for example) is created and you now have a proton (u-u-d) and a pi-0 meson (u-ubar). Exactly which pair gets created is random - you could create a d-dbar pair and be left with a neutron and a pi+, or many other possibilities. This is whay collisions in colliders like the LHC produce 'showers' or 'jets' of hadrons.

 

[Trenton]

Can anyone recommend any books or papers on the definitive proof quarks and gluons actually exist. Even better, have protons/neutrons been observed at different stages of separation in particle accelerators?

 

[tom.stoer]

Typically experimental results from deep inelastic scattering (DIS) experiments are regarded as proof for quarks and gluons. There is a so-called scaling regime where an electron scatters with a single quasi-free quark (fractional charge; reasoning similar to Rutherford scattering); certain sum rules indicate that there are three such objects within a nucleon; other results (e.g. three-jet) indicate the existence of gluons. In general both low-energy / nucleon physics as well as high-energy scattering is explained using QCD which is the dynamical theory of quarks and gluons.

Literature: books about elementary particle physics

 

[Trenton]

Thanks for that Tom. I just looked up some stuff of this on google and will settle down for a good read.

What I am specifically looking for though, is something that squares particles (including quarks) with their mass/energy and size. In just the same way as photons with a smaller wavelength have higher energy, the electron orbitals are spatially larger than the orbitals of nucleons which have more than 1800 times the mass/energy. I am wondering if quark orbitals are larger than those of protons or neutons - particularly since it seems most of the energy of the proton is binding energy (gluons) rathen than quarks.

I am also wondering how the strong force/gluons, which get stronger with distance, might behave under severe compression as in neutron stars. Might the insistance of quarks on a manage-a-trois also work against merging as hard as it works against separation and thereby thwart the collapse to a point that is supossedly the fate of nuetron stars of more than 3 solar masses?

 

[daschaich]

Literature: books about elementary particle physics

For non-technical audiences, I tend to recommend The Quantum Quark by Andrew Watson, though it's now been more than five years since I read it, and I'm beginning to get fuzzy on what particular details it covered.

 

[daschaich]

...electron orbitals are spatially larger than the orbitals of nucleons which have more than 1800 times the mass/energy...

Eek! You are mixing up some different concepts here. First of all, to the best of our knowledge electrons are elementary particles while nucleons are composites built out of other particles. It is possible to define the size of composite particles (though there are some subtleties involved), but we observe elementary particles (like electrons, quarks and gluons) to be point-like (that is, of zero size), at least down to a billionth of a nanometer.

Electron orbitals don't tell you anything about the size or mass of electrons, just about how close the electrons tend to be to the nuclei to which they are bound.

 

[Trenton]

I was to some extent, mixing deliberately. In contemplating the 'anatomy' of the fundamental particles (acknowledging nucleons as composites), I am instictive drawn (not scientific I know), to the idea that particles are really photons that somehow self-circle and chase their own tail. I tend to think of all particles (and composites) as being orbitals. I am equally fascinated by the anatomy of the photon.

This is like string theory I guess except that I am struggling to understand why one school of thought has it that there are 10 dimensions while another puts it at 11. Until I get to the bottom of that I will refrain from calling myself a string theorist.

 

[fzero]

I was to some extent, mixing deliberately. In contemplating the 'anatomy' of the fundamental particles (acknowledging nucleons as composites), I am instictive drawn (not scientific I know), to the idea that particles are really photons that somehow self-circle and chase their own tail. I tend to think of all particles (and composites) as being orbitals. I am equally fascinated by the anatomy of the photon.

There is no scientific basis for this picture. The photon is distinct from the other elementary particles. It's also not possible for a lone photon to form a closed orbit except in very esoteric or extreme conditions. It's not something that happens naturally.

You'd be well advised to start trying to read the wikipedia entries on elementary particles and then move on to some of the easier references you'll find listed there or earlier in this thread.

This is like string theory I guess except that I am struggling to understand why one school of thought has it that there are 10 dimensions while another puts it at 11. Until I get to the bottom of that I will refrain from calling myself a string theorist.

There really isn't one school of thought which says 10 and another which says 11. The idea behind M-Theory is that these are different corners of the same theory. When a particular coupling constant is small, the 10 dimensional description is good, when it is large, the 11 dimensional description is better. It's not really possible to begin to really understand this deeply without having a firm grasp on more tangible particle physics. So you really should get a better grounding in less speculative physics.

 

[ParticleGrl]

I was to some extent, mixing deliberately. In contemplating the 'anatomy' of the fundamental particles (acknowledging nucleons as composites), I am instictive drawn (not scientific I know), to the idea that particles are really photons that somehow self-circle and chase their own tail.

You immediately run into a problem. Photons are bosons- their fundamental property is that of symmetry. Switching two photons results in the same wavefunction.

Matter particles (nucleons, partons, electrons) are fermions- their fundamental property is that of anti-symmetry, switch two and the wavefunction develops a negative sign. You can't build something anti-symmetric out of symmetric objects.