% !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$TAG.tex
\documentclass[11pt,border=4pt]{standalone}
\usepackage{feynmp-auto}
\usepackage{xcolor}
\definecolor{colkappaf}{rgb}{1,0,0} % kappa_q (red)
\begin{document}
\begin{fmffile}{feyngraph}
  \fmfframe(4,13)(2,13){ % padding (L,T)(R,B)
  \begin{fmfgraph*}(70,60) % dimensions (WH)
    % line style
    \fmfset{wiggly_len}{12} % boson wavelength
    \fmfset{wiggly_slope}{65} % boson slope of waves
    % external vertices
    \fmfleft{i}
    \fmfright{o2,o1}
    % main
    \fmf{dashes,t=1.4}{i,v}
    \fmf{fermion}{o2,v,o1}
    % Higss coupling
    \fmfv{decor.shape=circle,decor.filled=full,decor.size=4,f=(1,,0,,0),
          l.d=5,l.a=115,l=\color{colkappaf}$\kappa_{f}$\hspace{-1pt}}{v}
    % labels
    \fmflabel{h}{i}
    \fmfv{l.a=25,l.d=5,l=$f$}{o1}
    \fmfv{l.a=-25,l.d=5,l=$\overline{f}$}{o2}
  \end{fmfgraph*}
  } % close \fmfframe
\end{fmffile}
\end{document}