\documentclass[border={20pt 0pt 30pt 0pt}]{standalone}
\usepackage{tikz}
\usepackage{tikz-feynman}

\tikzfeynmanset{every edge={thick}}

\begin{document}

\feynmandiagram [small, vertical=Wv to NW] {
nu[particle=$\nu_\ell$] -- [fermion] Wv -- [fermion] mu[particle=$\ell^{-}$],
Wv -- [boson, edge label=$W$, momentum'=$Q^2$] NW,
N[particle=$p$] -- [anti fermion] NW -- [anti fermion] P[particle=$n$],
};

\end{document}