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Thread: Does beta decay indicate that quarks are made of smaller particles?

  1. #1
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    Does beta decay indicate that quarks are made of smaller particles?

    That would seem to be the logical inference, but I've never heard it mentioned.
    "Occam" is the name of the alien race that will enslave us all eventually. And they've got razors for hands. I don't know if that's true but it seems like the simplest answer."

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  2. #2
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    I'm not sure I can see the logic behind that.

    The weak force is a flavour changing force - doesn't mean that there is some deeper layer underneath. Just that it can change isospin.

    Edit: If I am missing something obvious then please feel free to tell me, by the way, I just can't see a direct relationship between flavour changing currents and substructure.

  3. #3
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    If you can turn an up quark into a down quark by removing an electron or a positron, does that not indicate that a quark has component particles?
    "Occam" is the name of the alien race that will enslave us all eventually. And they've got razors for hands. I don't know if that's true but it seems like the simplest answer."

    Stephen Colbert.

  4. #4
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    Quote Originally Posted by parallaxicality View Post
    If you can turn an up quark into a down quark by removing an electron or a positron, does that not indicate that a quark has component particles?
    Well, there are (at least) two possibilities. One is that it's simply possible for a down quark to transform into an up quark, an electron, and an antineutrino, mediated by the weak force. That's the standard view. The second is what you seem to be suggesting, that an up quark is actually made of a down quark bound with an electron and an antineutrino in some way, which can escape under the right circumstances. But by that logic, a down quark has to be composite as well, doesn't it? It would be made of an up quark, a positron, and a neutrino. Doesn't that lead to an infinite regress?

    It seems like at some point, to prevent that sort of thing from happening and letting the system "bottom out", there have to be fundamental particles that are not composite, but I think they'd have to be able to transform from one type of particle into another to account for all the behavior that we've seen.
    Conserve energy. Commute with the Hamiltonian.

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    Quote Originally Posted by parallaxicality View Post
    If you can turn an up quark into a down quark by removing an electron or a positron, does that not indicate that a quark has component particles?
    I'm not sure it does. Photons can turn into electrons and positrons (as pairs) without being made of them or having substructure. Plus removing an electron/positron isn't what happens in the Standard Model. The quark changes flavour by emitting a W boson, which then decays into a lepton and a neutrino.

    There is also the problem that you have a strange kind of infinite loop possible for a long decay chain. You could have neutron-> proton + electron, then proton -> neutron + positron ... ... ... It is hard to reconcile that with these emitted particles being intrinsic to the quark.

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