% !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$TAG.tex
\documentclass[11pt,border=4pt]{standalone}
\usepackage{feynmp-auto}
\usepackage{xcolor}
\definecolor{colvtx}{rgb}{0,.1,1} % LQ vertex (blue)
\begin{document}
\begin{fmffile}{feyngraph}
  \fmfframe(1,4)(15,4){ % padding (L,T)(R,B)
  \begin{fmfgraph*}(120,125) % dimensions (WH)
    % line style
    \fmfset{dash_len}{10} % dashes length
    \fmfset{wiggly_len}{12} % boson wavelength
    \fmfset{wiggly_slope}{65} % boson slope of waves
    % external vertices
    \fmfleft{d,i2,m2,m1,i1,d} % add dummies 'd' for spacing
    \fmfright{b2,p2,o2,o1,p1,b1} % add dummies 'd' for spacing
    \fmfshift{3 down}{i1,p1}
    \fmfshift{3 up}{i2,p2}
    \fmfshift{7 down}{b1,o2}
    \fmfshift{7 up}{b2,o1}
    % incoming
    \fmf{gluon}{v1,i1}
    \fmf{gluon}{i2,v2}
    \fmf{phantom,t=0.6}{v1,p1,p2,v2} % pull gluons straight right
    \fmffreeze
    %%%% outgoing tau leptons
    %%%\fmf{fermion}{lq1,o1} % tau out
    %%%\fmf{fermion}{o2,lq2} % tau out
    %%%\fmf{phantom,t=0.5}{lq1,m1,m2,lq2} % pull taus straight left
    %%%\fmffreeze
    %%% outgoing b quarks from gluon splitting
    \fmf{fermion}{b1,v1}
    \fmf{fermion}{v2,b2}
    % t-channel
    \fmf{fermion}{v1,lq1} % t-channel
    \fmf{dashes,t=0.8,l.s=right,l.d=5,label=LQ}{lq1,lq2} % t-channel
    \fmf{fermion}{lq2,v2} % t-channel
    % outgoing tau leptons
    \fmf{fermion,t=0.9}{lq1,o1} % tau out
    \fmf{fermion,t=0.9}{o2,lq2} % tau out
    % vertices
    \fmfv{d.sh=circle,d.f=full,d.si=4,f=(0,,.1,,1),
          l=\color{colvtx}$\lambda$,l.d=6,l.a=90}{lq1}
    \fmfv{d.sh=circle,d.f=full,d.si=4,f=(0,,.1,,1),
          l=\color{colvtx}$\lambda$,l.d=6,l.a=-90}{lq2}
    % labels
    \fmfv{l.d=6,l.a=170,l=$g$}{i1}
    \fmfv{l.d=6,l.a=-170,l=$g$}{i2}
    \fmfv{l.d=6,l.a=10,l=$\tau^-$}{o1}
    \fmfv{l.d=6,l.a=0,l=\strut$\tau^+$}{o2}
    \fmfv{l.d=6,l.a=20,l=$\overline{\mathrm{b}}$}{b1}
    \fmfv{l.d=6,l.a=-20,l=b}{b2}
  \end{fmfgraph*}
  } % close \fmfframe
\end{fmffile}
\end{document}