% !TEX program = pdflatexmk
% !TEX parameter = -shell-escape
% Author: Izaak Neutelings (September 24)
% Instructions: To compile via command line, run the following twice
%   pdflatex -shell-escape extract/higgs_decay$TAG.tex
\documentclass[11pt,border=4pt]{standalone}
\usepackage{feynmp-auto}
\usepackage{xcolor}
\definecolor{colkappaV}{rgb}{.15,.75,.15} % kappa_V (green)
\begin{document}
\begin{fmffile}{feyngraph}
  \fmfframe(6,12)(14,12){ % padding (L,T)(R,B)
  \begin{fmfgraph*}(100,100) % dimensions (WH)
    % line style
    \fmfset{wiggly_len}{12} % boson wavelength
    \fmfset{wiggly_slope}{65} % boson slope of waves
    % external vertices
    \fmfstraight
    \fmfleft{i2,i,i1}
    \fmfright{o4,o3,o2,o1}
    % main
    \fmf{dashes,t=2}{i,v}
    \fmf{boson,t=1.5,l.d=5,l.s=right,label=Z}{v1,v,v2}
    \fmf{fermion,t=3}{o2,v1,o1}
    \fmf{fermion,t=3}{o4,v2,o3}
    \fmf{phantom,t=3}{v1,i1,i2,v2} % pull Zll vertices to left 
    % Higss coupling
    \fmfv{decor.shape=circle,decor.filled=full,decor.size=4,f=(.15,,.75,,.15),
          l.d=6,l.a=-10,l=\color{colkappaV}$\kappa_Z$}{v}
    % labels
    \fmflabel{h}{i}
    \fmfv{l.a=20,l.d=5,l=\vspace{4pt}\strut$\ell^-$}{o1}
    \fmfv{l.a=-20,l.d=5,l=\vspace{-6pt}\strut$\ell^+$}{o2}
    \fmfv{l.a=20,l.d=5,l=\vspace{4pt}\strut$\ell^-$}{o3}
    \fmfv{l.a=-20,l.d=5,l=\vspace{-6pt}\strut$\ell^+$}{o4}
  \end{fmfgraph*}
  } % close \fmfframe
\end{fmffile}
\end{document}