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Is Isospin Conversation Required In The Standard Model?

  1. May 26, 2015 #1

    ohwilleke

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    A new experimental result from BESIII finds that there is isospin violation in the decays of J/Psi mesons in a path involving scalar mesons (with a narrow width in tension with world averages) and notes that a previous experiment found isospin violation in another decay chain.

    http://arxiv.org/abs/1505.06283

    The paper's introduction, however, does little to present this finding in theoretical context. In particular, it doesn't explain the Standard Model expectation regarding isospin conservation or violation. I would think that isospin violation is permitted in the Standard Model, but only through flavor changing W boson interactions and only comparatively slowly at some small cross-section of the decay, and the paper is not at all clear regarding whether these kinds of W boson interactions are inferred.

    Can anyone shed light on whether the isospin violation observed at BESIII in this paper is BSM or SM physics?

    (Edited to add that the title should have said "Conservation" and not "Conversation". I'm quite certain that the Standard Model does not forbid discussions of isospin due to some grand cosmic conspiracy.)

    Partially answering my own question, a previous BESIII paper on another isospin violating decay has a better theoretical background section: http://arxiv.org/abs/1502.02641
     
    Last edited: May 26, 2015
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  3. May 26, 2015 #2

    Vanadium 50

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    Isospin is not an exact symmetry in the SM. For example, the phi(1020) decays to omega + pi0 a tiny fraction of the time.

    Why is this in BTSM?
     
  4. May 27, 2015 #3

    ohwilleke

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    I wasn't sure if it was SM or BSM, and so asked.
     
  5. Jun 1, 2015 #4
    IIUC left- and right-chirality leptons and quarks have different isospins, but they switch from left to right and back by interacting with nonzero ambient Higgs field. Thus, isospin is not a conserved charge in any vacuum with nonzero Higgs field.
     
  6. Jun 1, 2015 #5

    Vanadium 50

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    Nikkom, that's not isospin. That's weak isospin.
     
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