% !TEX program = pdflatexmk
% !TEX parameter = -shell-escape
% Author: Izaak Neutelings (September 24)
% Instructions: To compile via command line, run the following twice
%   pdflatex -shell-escape extract/ttbar$TAG.tex
\documentclass[11pt,border=4pt]{standalone}
\usepackage{feynmp-auto}
\begin{document}
\begin{fmffile}{feyngraph}
  \fmfframe(-5,15)(-2,15){ % padding (L,T)(R,B)
  \begin{fmfgraph*}(110,60) % dimensions (WH)
    % line style
    \fmfset{wiggly_len}{12} % boson wavelength
    \fmfset{wiggly_slope}{65} % boson slope of waves
    % external vertices
    \fmfleft{i2,i1}
    \fmfright{o2,o1}
    % main
    \fmf{gluon}{v1,i1}
    \fmf{gluon}{i2,v2}
    \fmf{fermion,t=0.8,l.s=right,label=t}{v1,v2} % t-channel
    \fmf{phantom}{v1,o1,o2,v2} % for balance
    \fmffreeze
    \fmf{fermion}{o2,v1}
    \fmf{fermion,rubout}{v2,o1}
    % labels
    \fmflabel{$g$}{i2}
    \fmflabel{$g$}{i1}
    \fmfv{l.d=5,l.a=25,l.s=left,l=t}{o1}
    \fmfv{l.d=5,l.a=-25,l=$\overline{\mathrm{t}}$}{o2}
  \end{fmfgraph*}
  } % close \fmfframe
\end{fmffile}
\end{document}