TeX source:
\begin{fmffile}{schanneltwo} \begin{fmfgraph*}(100,60) \fmfpen{thick} \fmfleftn{i}{2}\fmfrightn{o}{4} \fmflabel{$e_-$}{i1}\fmflabel{$e_+$}{i2} \fmflabel{$\noexpand\bar c$}{o1} \fmflabel{$\nu_{\mu}$}{o2} \fmflabel{$\mu_+$}{o3} \fmflabel{$s$}{o4} \fmfpen{thick} \fmf{boson,label=$\gamma,,Z$}{v1,v2} \fmf{fermion}{i1,v1,i2} \fmf{fermion}{o1,v2,v3,o4} \fmffreeze \fmf{boson}{v3,v4}\fmf{fermion}{o3,v4,o2} \fmfdotn{v}{4} \end{fmfgraph*} \end{fmffile}