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Homework Help: Feynman Diagram: Simga+ -> p + gamma?

  1. May 2, 2012 #1
    Feynman Diagram: Simga+ --> p + gamma?


    Can anyone give me some indications as to how to draw the feynman diagram for the following decay?

    Ʃ+ → p + [itex]\gamma[/itex]

    Should I consider the quark composition of the sigma first?

    Thanks a lot.
  2. jcsd
  3. May 3, 2012 #2
    Re: Feynman Diagram: Simga+ --> p + gamma?

    Indeed. All of the QED/QCD interactions involve individual quarks and leptons, not composite particles. So you want to consider what happens to each quark in the sigma particle independently (at least, to get a first approximation to the decay).
  4. May 4, 2012 #3
    Re: Feynman Diagram: Simga+ --> p + gamma?

    So I get how the two u quarks would combine with a d quark to form the proton, but would you get this d quark with the s quark that's left?

    Is the process s --> u + anti u ---> ONE gamma allowed?
  5. May 4, 2012 #4


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    Re: Feynman Diagram: Simga+ --> p + gamma?

    No, that process does not conserve electric charge. What weak interaction processes involving quarks did you learn about?
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