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Groups of quarks and confinement

  1. Sep 22, 2008 #1
    hey guys,

    I am a first year physics student but my physics lecturer invited me to sit in during her third year physics lecture.

    Of course i didnt fully understand some of it, but i think i at least grasped the concept of confinement (the lecture was on quantum chromodynamics by the way). My question is: if quarks are unable to seperate once they are within a certain distance feom eachother, would it not be the case that groups of quarks passing by eachother within this distance would form one larger group? And would this not continue until there was just a huge clump of quarks all unable to escape eachother??

    Sorry if my question is unclear, as i said i am only a first year and i may have the wrong idea about confinement in general. If so please try and put me on the right track.

    Thanks,
    -spoon
     
  2. jcsd
  3. Sep 22, 2008 #2

    clem

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    Because quarks come in three "colors" and their wave function is antisymmetric in the color degree of freedom, no more than three quarks can be in one confined state.
    Extra quark-antiquark pairs may be included.
     
  4. Sep 22, 2008 #3
    thanks for the reply.

    Would the scenario be able to occur for pairs of quarks I.e those groups that make up mesons (I think).

    Although I suppose there would be no single quarks around in that case since they would already be confined with at least one other quark so that the smallest group of quarks ever passing by each other would be four, and as you described impossible to form one larger clump...?

    If there were two groups of two quarks, say a & b, then if they were close enough would it be possible for one quark in a to be placed within the confinement distance(??) of both groups a & b, while the other quark in a was not within this distance of the b group? If so what would happen in this case?

    Sorry if that is unreadable my train of thought just kinda kept going. If i have contradicted something you wrote in your post i apologize, i didnt fully understand it. So if i have done it is unintentionally.

    Thanks,
    -spoon
     
  5. Sep 22, 2008 #4
    Hi,

    first, what we see in Nature are groups consisting either of [itex]q\bar{q}[/itex] or [itex]qqq[/itex]. Anything beyond is speculation.

    Some people would argue that from the point of view of group theory, there is no good reason to discard arrangements such as [itex]qg\bar{q}[/itex] or [itex]qqqq\bar{q}[/itex], and indeed we search for those configurations !, but so far they have never been confirmed.

    However, it is clear that [itex]qq[/itex] is not bound. It would help to avoid running into serious difficulties if you would not think in terms of a single quark around, because there is no such thing either. If you insist to go there, we will need to discuss deeper what are real and virtual particles, which is an essential prerequisite for quarks and gluons, which are permanently confined beast into objects smaller than their own Compton wavelength. It is best to think at first of hadrons as bags containing a well-defined number of quarks/antiquarks. Now take hadrons and re-design gedankenexperiments :smile:
     
  6. Sep 22, 2008 #5
    thanks guys, together that actually does kinda clear stuff up a bit :)

    Looking forward to studying physics at a higher level. Perhaps in a few years I will be able to hold a more intelligent conversation about the subject matter. Cant wait!!

    Cheers,
    -spoon
     
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