# Normalization condition

1. Feb 26, 2010

### nklohit

In Peskin's textbook, he uses the spin sum as $$\sum u\bar{u} = \gamma^{\mu}p_{\mu} +m$$ ;
on the other hand, in Kaku's book and in Zee's book, they use $$\sum u\bar{u} = \dfrac{\gamma^{\mu} p_{\mu} + m}{2m}$$ . But why aren't there any diffferent in the differential cross
section formula ?

2. Feb 26, 2010

### clem

The normalization condition should not affect any physical result.