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Homework Help: Pair-Production problems

  1. Feb 21, 2007 #1
    1. The problem statement, all variables and given/known data

    How much photon energy would be required to produce a proton-antiproton pair? Give the answer in SI units.

    2. Relevant equations

    3. The attempt at a solution

    I seem to be confused I know the KE would be zero I also know this would not exist in real life but I need to find the min energy so KE of the photon pairs is 0. I am not sure if the equation has to do with the mass of a photon or the momentum of the photons. In either case I don't know what the mass of a photon would be. I read it was zero but can't figure out how to use this formula then.
  2. jcsd
  3. Feb 21, 2007 #2


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    Homework Helper

    ok... mass of a photon is zero... I think we all know that. But its momentum is not... we can agree on that too I think. Now, your key equation is
    [tex]E^2=p^2 c^2+m^2 c^4[\tex]
    where m here is the rest mass of your particle, p is its momentum and E is its total energy. To do your question: remember 4-momentum is conserved.....etc
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