\documentclass{standalone}

\usepackage{tikz}
\usetikzlibrary{decorations.pathmorphing}
\usetikzlibrary{decorations.markings}
\usetikzlibrary{patterns}

\begin{document}

\begin{tikzpicture}[decoration={
    markings,
    mark=at position 0.5 with {\arrow{>}}}
    ] 


	\draw[thick,postaction={decorate}]  (-2,3) node[left] {$\nu_\mu$} -- (0,2) ; % incoming top
	\draw[thick,postaction={decorate}]  (0,2) -- (2,3) node[right] {$\mu^-$} ; % outgoing top
	\draw[draw=white,double=black, very thick, decorate, decoration=snake] (0,2) -- (0,1) node[right,pos=0.5] {$W^{+}$};


	\draw[thick,postaction={decorate}] (-2,0) node[left] {$e^{-}$} -- (0,1); % ingoing bottom
	\draw[thick,postaction={decorate}] (0,1) -- (2,0) node[right] {$\nu_e$} ; % ingoing bottom

\end{tikzpicture}

\end{document}
