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Quarks in hadrons

  1. Jul 24, 2015 #1

    BiGyElLoWhAt

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    So, I have a question, and maybe we don't have an answer, or maybe it's a simple answer.
    I was thinking, and if we have a pentaquark, I'm pretty sure we have to have a quark-antiquark pair (of any color-anticolor) and 3 quarks (one of each color). If, per say, the quark and antiquark were adjacent, I would think it would tend to eject itself from the particle, due to the superposition of the sum of charge appearing as essentially zero to the other 3 quarks. The same would apply to the 3 quarks with respect to the quark-antiquark pair.

    When you take into account asymptotic freedom, where the strong force approaches zero as distance approaches zero, any "net" force on these quarks should be negligible. This seems to imply that the quark antiquark pair have another quark inbetween them that they can bond to, to maintain the pentaquark for a ~non-zero amount of time (I know the lifespan was really short). This would also imply that for a stable pentaquark, that the quark-antiquark pair and the quark inbetween would have to be unable to exchange gluons with the environment (otherwise one of them could end up as the same color as an adjacent quark, and be ejceted, effectively causing the pentaquark to decay), or there would have to be simultaneous gluon absorbsion/emission to compensate and maintain its stability (again, I know this particle was highly unstable).

    So with this presumable position dependence on the formation of a true pentaquark (contrary to a meson-baryon pair like is also being speculated about), wouldn't this imply a lack of superposition? (i.e. the quarks must be in a certain configuration, and we know their positions relative to each other)

    If not, then where is the flaw in this logic? I am apparently missing something.
    Thanks in advance.
     
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  3. Jul 24, 2015 #2

    mfb

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    The whole approach does not make sense. Also keep in mind that personal theories are against the forum rules.

    "adjacent" doesn't mean anything in hadrons.
    Why?
    It does not do that.
     
  4. Jul 24, 2015 #3

    BiGyElLoWhAt

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    It's not a theory, I'm trying to understand the physics behind it.
    Are you saying there is absolutely no position dependance?
    Because quark confinement.
    "In https://www.physicsforums.com/wiki/Physics [Broken], asymptotic freedom is a property of some https://www.physicsforums.com/wiki/Gauge_theory [Broken] that causes bonds between particles to become asymptotically weaker as https://www.physicsforums.com/wiki/Energy [Broken] increases and https://www.physicsforums.com/wiki/Length_scale [Broken] decreases."
    https://en.wikipedia.org/wiki/Asymptotic_freedom
    Perhaps I should have used bond? I feel like bond and force are pretty much inerchangable in this context.[/QUOTE]
     
    Last edited by a moderator: May 7, 2017
  5. Jul 24, 2015 #4

    mfb

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    "The position of a quark" is not a meaningful concept. Quarks are not billard balls, they do not have well-defined positions.
    That does not make sense.

    The important point here is "energy increases". Hadrons are not massive particle accelerators.
     
    Last edited by a moderator: May 7, 2017
  6. Jul 24, 2015 #5

    BiGyElLoWhAt

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    I understand that they shouldn't, that was pretty much the point of my spiel.
    From what I understand, quark confinement is a result of superposition of distant color charges appearing as color neutral to a color charge at some large (in terms of hadrons) distance, and also the fact that the coupling constant increases in distance. Mesons are a result of quark confinement. The superposition of charge was also a high point that I mentioned.
    Let me quote the next line:
    "Asymptotic freedom is a feature of https://www.physicsforums.com/wiki/Quantum_chromodynamics [Broken] (QCD), the https://www.physicsforums.com/wiki/Quantum_field_theory [Broken] of the https://www.physicsforums.com/wiki/Strong_nuclear_force [Broken] between https://www.physicsforums.com/wiki/Quarks [Broken] and https://www.physicsforums.com/wiki/Gluon [Broken], the fundamental constituents of nuclear matter." Same wikipedia page as before.

    Edit* What does "Hadrons are not massive particle accelerators." mean?
     
    Last edited by a moderator: May 7, 2017
  7. Jul 25, 2015 #6

    mfb

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    The logic is the opposite - quark confinement makes sure separate objects are color-neutral.
    It does not. It increases with decreasing energy.

    It means you see asymptotic freedom if you look at hadron collisions with ~10 GeV or more energy. Hadrons don't have 10 GeV on their own (not counting the b quark masses).
     
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