% !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/ttbarV$TAG.tex
\documentclass[11pt,border=4pt]{standalone}
\usepackage{feynmp-auto}
\begin{document}
\begin{fmffile}{feyngraph}
  \fmfframe(-9,10)(6,10){ % padding (L,T)(R,B)
  \begin{fmfgraph*}(110,65) % dimensions (WH)
    % line style
    \fmfset{wiggly_len}{12} % boson wavelength
    \fmfset{wiggly_slope}{65} % boson slope of waves
    % external vertices
    \fmfleft{i2,m,i1}
    \fmfright{o2,z,o1}
    % skeleton
    \fmf{gluon,t=1.2}{v1,i1}
    \fmf{gluon,t=1.2}{i2,v2}
    \fmf{fermion}{v1,o1}
    \fmf{fermion}{o2,v2}
    \fmffreeze
    % Z boson
    \fmf{fermion,t=1}{v2,v,v1}
    \fmf{dashes}{z,v} % Z boson
    % labels
    \fmfv{l.a=158,l.d=5,l=$g$}{i1}
    \fmfv{l.a=-158,l.d=5,l=$g$}{i2}
    \fmfv{l.a=22,l.d=5,l=\strut t}{o1}
    \fmfv{l.a=0,l.d=4,l=Z}{z}
    \fmfv{l.a=-22,l.d=5,l=\strut$\overline{\mathrm{t}}$}{o2}
  \end{fmfgraph*}
  } % close \fmfframe
\end{fmffile}
\end{document}