% !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$TAG.tex
\documentclass[11pt,border=4pt]{standalone}
\usepackage{feynmp-auto}
\begin{document}
\begin{fmffile}{feyngraph}
  \fmfframe(-7,15)(-4,16){ % padding (L,T)(R,B)
  \begin{fmfgraph*}(110,60) % dimensions (WH)
    % line style
    \fmfset{wiggly_len}{12} % boson wavelength
    \fmfset{wiggly_slope}{65} % boson slope of waves
    % external vertices
    \fmfleft{i2,i1}
    \fmfright{o2,o1}
    \fmfshift{2 left}{i1}
    % main
    \fmf{gluon}{v1,i1}
    \fmf{gluon}{v1,i2}
    \fmf{gluon,label.side=left,label=$g$}{v1,v2} % s-channel
    \fmf{fermion}{o2,v2,o1}
    % labels
    %\fmflabel{$g$}{i1}
    %\fmflabel{$g$}{i2}
    \fmfv{l.d=4,l=$g$}{i1} % more control
    \fmfv{l.d=6,l=$g$}{i2} % more control
    \fmflabel{t}{o1}
    \fmflabel{$\overline{\mathrm{t}}$}{o2}
    %\fmflabel{$i\sqrt{\alpha}$}{v1}
    %\fmflabel{$i\sqrt{\alpha}$}{v2}
  \end{fmfgraph*}
  } % close \fmfframe
\end{fmffile}
\end{document}