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Threshold energy of a photoproduction

  1. Jun 19, 2008 #1
    hi,
    I have the reaction:

    (photon) + (proton) ---> (neutron) + (pion+)

    I have to find the minimum energy of the photon.
    A first condition can be that total energy of photon and proton has to be at least the mass energy of the output, but I don't think this can be a satisfying solution...

    When I try to include quadrimomentum conservation, calculus becomes very complex and I cannot find a solution...
    Suggestions?

    Thanks.
     
  2. jcsd
  3. Jun 19, 2008 #2

    malawi_glenn

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    what is "quadrimomentum " ?

    Hint: work in center of mass frame -> what is the threshold condition for the final state?
     
  4. Jun 19, 2008 #3

    George Jones

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    4-momentum, I suspect. :smile:
     
  5. Jun 19, 2008 #4

    malawi_glenn

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    yeah, I also suspected that hehe

    OP: search for "invariant mass", that is all you need, that quantity is both lorentz invariant and conserved. Also look at the hint I gave you earlier.
     
  6. Jun 19, 2008 #5
    yeah, It is 4-momentum
    I have tried both in lab and in center of mass frame, but it is too much complex...
     
  7. Jun 19, 2008 #6

    malawi_glenn

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    This is infact a super easy task, can you show work done?

    Can you try to answer my hint-question, "what is the threshold condition for the final state?"
     
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