- #1

- 12

- 5

- TL;DR Summary
- I did not understand one step in the QFT and Standard Model book from Matthew D. Schwartz.

Can someone please explain to me how can we obtain this integral in eq. 5.27 from eq. 5.26? I quite do not understand how is it possible to make this adjustment and why the (p_(f))^2 appeared there in the numerator and also why a solid angle appeared there suddenly.