% !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/ttbarqqbar$TAG.tex
\documentclass[11pt,border=4pt]{standalone}
\usepackage{feynmp-auto}
\begin{document}
\begin{fmffile}{feyngraph}
  \fmfframe(-9,13)(4,15){ % padding (L,T)(R,B)
  \begin{fmfgraph*}(120,90) % dimensions (WH)
    % line style
    \fmfset{wiggly_len}{13} % boson wavelength
    \fmfset{wiggly_slope}{68} % boson slope of waves
    % external vertices
    \fmfleft{i2,i1}
    \fmfright{o4,o3,o2,o1}
    \fmfshift{4 up}{o1,o2}
    \fmfshift{4 down}{o4,o3}
    % skeleton
    \fmf{gluon,t=2.5}{v1,i1}
    \fmf{gluon,t=2.5}{i2,v2}
    \fmf{fermion}{v1,o1}
    \fmf{fermion}{o4,v2}
    % qq -> ttbar
    \fmf{fermion,t=1.4}{vt1,v1}
    \fmf{fermion,t=1.4}{v2,vt2}
    \fmf{fermion}{o2,vt1}
    \fmf{fermion}{vt2,o3}
    \fmf{boson,t=1.2,label=$\gamma^*$\color{}!/Z,l.s=right,l.d=5}{vt1,vt2} % t-channel
    % labels
    \fmfv{l.a=158,l.d=6,l=$g$}{i1}
    \fmfv{l.a=-158,l.d=6,l=$g$}{i2}
    \fmfv{l.a=22,l.d=6,l=t}{o1}
    \fmfv{l.a=20,l.d=4,l=$\overline{\mathrm{t}}$}{o2}
    \fmfv{l.a=-20,l.d=4,l=t}{o3}
    \fmfv{l.a=-22,l.d=6,l=$\overline{\mathrm{t}}$}{o4}
  \end{fmfgraph*}
  } % close \fmfframe
\end{fmffile}
\end{document}