\documentclass[english]{article}

\usepackage{feyn}

\makeatother

\usepackage{babel}

\begin{document}

\section{Feynam Diagrams }


and your ready for something like that:

\[
\Diagram{\vertexlabel^{e^{-}} & \, & \vertexlabel^{e^{+}}\\
\momentum{fdV}k &  & \momentum{fuV}{k'}\\
 & g\\
\momentum{fuA}{p'} &  & \momentum{fdA}p\\
\vertexlabel_{e^{-}} &  & \vertexlabel_{e^{+}}}
\]

\end{document}