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Decay of pion

  1. Mar 23, 2009 #1
    Why the decay of neutral pion to electron positon pair is forbidden?
     
    Last edited: Mar 23, 2009
  2. jcsd
  3. Mar 23, 2009 #2
    Last edited: Mar 23, 2009
  4. Mar 23, 2009 #3

    blechman

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    you know, way back when i wrote down on a test that this decay was forbidden. my professor has a good laugh: he told me that i just "disproved" his PhD thesis!
     
  5. Mar 23, 2009 #4

    malawi_glenn

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    it is not forbidden, I did my Diploma thesis on that decay! ;-P

    i.e I am in the same situation as blechman's teacher was ;-)
     
  6. Mar 23, 2009 #5

    clem

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    The decay into electron-positron has to proceed through two virtual photons, one leading to the e-p pair and the other being absorbed by one of the pair. This makes the pi-->e p
    rate much slower than the two gamma decay.
    If the term "forbidden" is used in the way it is used in beta decay, then the e-p is
    "forbidden", as confirmed by the experimental rate.
     
  7. Mar 23, 2009 #6

    malawi_glenn

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    it is second order, so it depends on what one means by "forbidden"
     
  8. Mar 23, 2009 #7
    Here I think it means that it violates helicity conservation (which is expected for the leading order in the Bjorken limit).
     
  9. Mar 31, 2009 #8
    Isn't it also helicity suppressed?
     
  10. Mar 31, 2009 #9

    malawi_glenn

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    yes, see the post above yours =)
     
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