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When can we ignore the delta function in th Feynman rules?

  1. May 29, 2008 #1
    in peskin-schroeder and http://www.hep.phy.cam.ac.uk/batley/particles/handout_04.pdf" [Broken] the amplitude for [tex] e^-e^+\rightarrow \mu^- \mu^+ [/tex] is written using feynman rules as follows
    [tex] -iM=[\bar{v}(p_2)(-ie\gamma^\mu )u(p_1)] \frac{-ig_{\mu\nu}}{q^2}[\bar{u}(k_1)(-ie\gamma^\nu )v(k_2)] [/tex]

    but what about the delta function integeration? is it already done here?

    thanks in advanced!
    Last edited by a moderator: May 3, 2017
  2. jcsd
  3. May 29, 2008 #2
    I may well be wrong here, but that looks like the M matrix part of the S matrix, and it is the S matrix that has the delta function in it, so you shouldnt be expecting a delta function.

    again i DID only just do this, so i may be wrong.
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