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Homework Help: Up, anti-up quark annihilation feynman diagram

  1. May 2, 2010 #1
    1. The problem statement, all variables and given/known data

    At the Tevatron you observe the process u ̅u → τ+τ. Draw the lowest order Feynman diagrams for the processes involved and state which interactions are
    responsible. Label all internal lines, external lines and vertices

    [u = up quark, τ = tau lepton]

    3. The attempt at a solution

    Once i have the basic feynman diagram i can eaily label the internal/external lines and the vertices, however i'm simply having a problem identifying the diagram. From what i can think of right now i would assume the weak force (W-) is the process involved which would be just like a time reversed tau decay, however i can't picture how the feyman diagram would look?
  2. jcsd
  3. May 2, 2010 #2


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    It can't be mediated by the W because you won't be able to conserve charge at the vertices. You can rule out gluons because they don't couple to leptons, so what else is left?
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