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Pion 0 decay

  1. Oct 16, 2015 #1
    Hello everyone,
    I found in the PDG booklet that pi 0 decay into e+ e- gamma is more likely to happen than to e+ e- only ..is there a reason that favorises the first decay?
     
  2. jcsd
  3. Oct 16, 2015 #2

    Orodruin

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    The decay to a single electron-positron pair is suppressed because what would be the leading order contribution, the diagram with the exchange of one single photon, evaluates to zero.
     
  4. Oct 17, 2015 #3
    I didn't understand what you mean here. Would you please clarify. Thanks a lot
     
  5. Oct 17, 2015 #4

    Orodruin

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    The decays must happen via an intermediate state. The intermediate state which would be contributing the most to the electron-positron decay based on the couplings is not allowed.
     
  6. Oct 17, 2015 #5
    Any resource detailing that ? So grateful
     
  7. Oct 17, 2015 #6

    Orodruin

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    Complete understanding of this would require an introductory course in quantum field theory, usually given at universities somewhere in year 3-4.
     
  8. Oct 17, 2015 #7
    Thanks a lot
     
  9. Oct 17, 2015 #8

    Hepth

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    also helicity suppression probably plays a role. a pseudoscalar decaying to to leptons will be suppressed by the mass of the lepton, due to conservation of angular momentum requiring a spin flip on one lepton. adding the photon will allow the lepton to not have to flip, thus trading the mass suppression for alphaEM.
     
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