# Kähllén-Lehmann formula and MS scheme

1. Sep 18, 2012

### eoghan

Hi everybody!
Using "physical normalization conditions" I find for the electron self energy
$$Z_2^{-1}=1-\frac{d\Sigma}{dp}(p=m)$$
where $m$ is the physical mass of the electron. Then $Z_2$ is the same constant appearing in the Kähllén-Lehmann representation (it is the residue at the pole of the physical propagator).
However, if I compute $Z_2$ in MS scheme, can I say that the $Z$ I found is not the same $Z$ in Kähllén-Lehmann?