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Homework Help: 4-momentum problem

  1. Sep 21, 2005 #1
    I'm having trouble understanding conservation of 4-momentum. My problem is about dertermining the threshold for triplet production from a photon and an electron using 4-momentum conservation. The answer is 4m0c^2. So far, I say the initial energy is:

    E1^2=(pc)^2 + (m0c^2)^2=(hv)^2+(m0c^2)^2

    At threshold energy after collision, three particles with no momentum are produced, so


    E1=E2, but substituting and solving for hv does not work out correctly, and I have not used 4-momentum at all anyhow. What am I doing wrong/forgetting? Help!
  2. jcsd
  3. Sep 21, 2005 #2


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    Science Advisor

    It might help to know what the question actually asks.
  4. Sep 21, 2005 #3
    verbatim- "Show the threshold for triplet production is 4m0c^2 using the concept of conservation of 4-momentum." Sorry for the paraphrase.
    Last edited: Sep 21, 2005
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