# Cross Section Calculus

In the book "Gauge Theories of the strong, weak, and electromagnetic interactions" by Chris Quigg the calculus of the scattering of proton-electron is esbosed (chapter 7, section 3 , pag 168).

He get the result (in the lab frame):

$$\frac{\mbox d^2\sigma}{\mbox d E^\prime\mbox d\Omega^\prime} =\frac1{16\pi^2}\frac{E^\prime}{E}\bar{|\mathcal M|}^2$$.

I'm new to this kind of calculus, but couldn't get this.

Does Anyone have a suggestion?.

reilly