% !TEX program = pdflatexmk
% !TEX parameter = -shell-escape
% Author: Izaak Neutelings (September 25)
% Instructions: To compile via command line, run the following twice
%   pdflatex -shell-escape extract/ttbar$TAG.tex
\documentclass[11pt,border=4pt]{standalone}
\usepackage{feynmp-auto}
\begin{document}
\begin{fmffile}{feyngraph}
  \fmfframe(-8,18)(-5,16){ % padding (L,T)(R,B)
  \begin{fmfgraph*}(120,70) % dimensions (WH)
    % line style
    \fmfset{wiggly_len}{12} % boson wavelength
    \fmfset{wiggly_slope}{65} % boson slope of waves
    % external vertices
    \fmfleft{i2,i1}
    \fmfright{o2,o1}
    \fmftop{t}
    \fmfshift{5 up}{t}
    % skeleton
    \fmf{phantom}{i1,v1,i2}
    \fmf{phantom}{v1,v2}
    \fmf{phantom}{o1,v2,o2}
    \fmffreeze
    % main
    \fmf{fermion}{i1,g}
    \fmf{plain,tension=2.8}{g,v1}
    \fmf{fermion}{v1,i2}
    \fmf{gluon,tension=0}{t,g}
    \fmf{gluon}{v1,v2}
    \fmf{fermion}{o2,v2,o1}
    % labels
    \fmflabel{$q$}{i1}
    \fmflabel{$\overline{q}$}{i2}
    \fmfv{l.d=5,l.a=25,l=$g$}{t}
    \fmflabel{$\mathrm{t}$}{o1}
    \fmflabel{$\bar{\mathrm{t}}$}{o2}
  \end{fmfgraph*}
  } % close \fmfframe
\end{fmffile}
\end{document}