% !TEX program = pdflatexmk
% !TEX parameter = -shell-escape
% Author: Izaak Neutelings (March 25)
% Instructions: To compile via command line, run the following twice
%   pdflatex -shell-escape extract/LQ$TAG.tex
\documentclass[11pt,border=4pt]{standalone}
\usepackage{feynmp-auto}
\usepackage{xcolor}
\definecolor{colqcd}{rgb}{1,0,0} % strong vertex (red)
\begin{document}
\begin{fmffile}{feyngraph}
  \fmfframe(3,14)(14,11){ % padding (L,T)(R,B)
  \begin{fmfgraph*}(140,100) % dimensions (WH)
    % line style
    \fmfset{dash_len}{10} % dashes length
    \fmfset{wiggly_len}{12} % boson wavelength
    \fmfset{wiggly_slope}{65} % boson slope of waves
    % external vertices
    \fmfstraight
    \fmfleft{i2,i1}
    \fmfright{o4,o3,o2,o1}
    \fmfshift{10 down}{i1}
    \fmfshift{10 up}{i2}
    % internal vertices (exact placement)
    \fmfforce{(.80w,.82h)}{lq1} % exact placement
    \fmfforce{(.80w,.18h)}{lq2} % exact placement
    % gg -> g
    \fmf{gluon}{v1,i1}
    \fmf{gluon}{i2,v1}
    \fmf{gluon,t=1.1}{v1,v2} % s-channel
    % g -> LQ LQ
    \fmf{dashes,t=1.2,l.s=left,label=LQ}{v2,lq1}
    \fmf{dashes,t=1.2,l.s=right,label=$\overline{\mathrm{LQ}}$}{v2,lq2}
    % LQ -> ql
    \fmf{fermion}{o2,lq1,o1}
    \fmf{fermion}{o3,lq2,o4}
    % vertex
    \fmfv{d.sh=circle,d.f=full,d.si=4,f=(1,,0,,0),
          l=\strut\color{colqcd}$\alpha_\mathrm{s}$,l.d=6,l.a=0}{v2}
    % labels
    \fmfv{l.a=150,l.d=4,l=$g$}{i1}
    \fmfv{l.a=-150,l.d=4,l=$g$}{i2}
    \fmfv{l.a=25,l=$\tau^-$}{o1}
    \fmfv{l.a=-20,l=$\overline{\mathrm{b}}$}{o2}
    \fmfv{l.a=25,l=$\tau^+$}{o3}
    \fmfv{l.a=-20,l=\vspace{-2pt}b}{o4}
  \end{fmfgraph*}
  } % close \fmfframe
\end{fmffile}
\end{document}