Peskin and Schroeder eq. 18.84

  • #1

Homework Statement

So I am self-studying the book of Peskin&Schroeder, and there is something I don't understand on page 616.

In eq. 18.80, there is a numerical factor of ½ and going from e2 to α will introduce a factor 4π when proceeding to eq. 18.84. But then there should be a numerical factor of 2π in eq 18.84. What gives an extra factor of 2?

Homework Equations


(this is the first time I post here, please do tell if uploading a page in this format is not acceptable)

The Attempt at a Solution

I believe I understand the rest of the calculation on this page.
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Answers and Replies

  • #2
Well, equation (18.80) is for ##e^+e^-\rightarrow e^+e^-##, equation (18.84) is for ##e^+e^-\rightarrow \text{hadrons}##. As the text says, the two are related by the optical theorem.

Suggested for: Peskin and Schroeder eq. 18.84