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Photon-Photon interactions

  1. Jan 10, 2013 #1
    When two high energy photons collide with each other, what determines whether a pair production results or whether a photon-photon scattering results? I hope my question makes sense.
  2. jcsd
  3. Jan 10, 2013 #2


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    It is random (and most of the time, nothing happens), as all collisions in particle physics.
    Pair production requires at least 1 MeV center of mass energy, of course.
  4. Jan 10, 2013 #3
    So a collision that can result in pair production can just as well result in scaterring, with no reason why one occurs and not the other?
  5. Jan 10, 2013 #4


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    That's what the man said.
  6. Jan 10, 2013 #5
    Just checking. I thought there was more to it than that.
  7. Jan 10, 2013 #6


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    This is not to say that they're equally probable though.

    In particular, the diagram involving pair production is at tree level whereas the interaction term is one loop.
  8. Jan 11, 2013 #7
    you can just use the mandelstam variable S(there are three) which represents total energy to decide which one has more possibility over other.for scattering in which S<< 4ml2,the cross section σ=α4S3/ml8,for box graph.and for
    S>> 4ml2
    for single pair production,
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