% !TEX program = pdflatexmk
% !TEX parameter = -shell-escape
% Author: Izaak Neutelings (December 24)
% Instructions: To compile via command line, run the following twice
%   pdflatex -shell-escape extract/singletop$TAG.tex
\documentclass[11pt,border=4pt]{standalone}
\usepackage{feynmp-auto}
\begin{document}
\begin{fmffile}{feyngraph}
  \fmfframe(-7,10)(-1,10){ % padding (L,T)(R,B)
  \begin{fmfgraph*}(100,50) % dimensions (WH)
    % line style
    \fmfset{wiggly_len}{12} % boson wavelength
    \fmfset{wiggly_slope}{65} % boson slope of waves
    % external vertices
    \fmfleft{i2,i1}
    \fmfright{o2,o1}
    % main
    \fmf{fermion}{i1,v1,o1} % top quark
    \fmf{fermion}{i2,v2,o2}
    \fmf{boson,t=0.7,t=0,l.s=left,l.d=4,label=W}{v2,v1} % t-channel
    % labels
    \fmfv{l.d=6,l.a=158,l=b}{i1}
    \fmfv{l.d=6,l.a=-158,l=$q$}{i2}
    \fmfv{l.d=6,l.a=22,l=t}{o1}
    \fmfv{l.d=6,l.a=-20,l=$q'$}{o2}
  \end{fmfgraph*}
  } % close \fmfframe
\end{fmffile}
\end{document}