How to resize Feynman diagrams drawn with FeynMF / FeynMP (and their labels)?

Question

This seems like an easy question, but I haven't found any hints on this, so: How do I resize the output of FeynMF and the labels within it?

I use it like this:

\begin{enumerate}
  \item Feynman diagram:\\
    \begin{fmffile}{fgraph_tau}
      \begin{fmfgraph*}(8,5)
        \fmfleft{i1,i0}
        \fmfright{o1,o0}
        \fmf{fermion,label=$e^+$}{i1,w1}
        \fmf{fermion,label=$\overline\nu_e$}{w1,o1}
        \fmf{boson,label=$W$}{w0,w1}
        \fmf{fermion,label=$\overline\nu_\mu$}{i0,w0}
        \fmf{fermion,label=$\mu^+$}{w0,o0}
      \end{fmfgraph*}
    \end{fmffile}
  ...
\end{enumerate}

and compile using this SE answer, which gives a nice Feynman diagram in the output pdf in the place I'd like it to be.

Now I would like to have a) the labels a bit larger and b) the overall graph itself a bit smaller. How can I achieve this?

Answer 1

The size of the diagram is controlled by \unitlength; you can also issue a font size changing command for increasing the size of the letters.

\documentclass{article}
\usepackage{feynmp-auto}
\begin{document}
\begin{enumerate}
  \item Feynman diagram:
    \begin{fmffile}{fgraph_tau}
      \setlength{\unitlength}{1cm}
      \begin{fmfgraph*}(8,5)
        \fmfleft{i1,i0}
        \fmfright{o1,o0}
        \fmf{fermion,label=$e^+$}{i1,w1}
        \fmf{fermion,label=$\overline\nu_e$}{w1,o1}
        \fmf{boson,label=$W$}{w0,w1}
        \fmf{fermion,label=$\overline\nu_\mu$}{i0,w0}
        \fmf{fermion,label=$\mu^+$}{w0,o0}
      \end{fmfgraph*}
    \end{fmffile}

  \item Smaller Feynman diagram:
    \begin{fmffile}{fgraph_tau2}
      \setlength{\unitlength}{.75cm}\large
      \begin{fmfgraph*}(8,5)
        \fmfleft{i1,i0}
        \fmfright{o1,o0}
        \fmf{fermion,label=$e^+$}{i1,w1}
        \fmf{fermion,label=$\overline\nu_e$}{w1,o1}
        \fmf{boson,label=$W$}{w0,w1}
        \fmf{fermion,label=$\overline\nu_\mu$}{i0,w0}
        \fmf{fermion,label=$\mu^+$}{w0,o0}
      \end{fmfgraph*}
    \end{fmffile}
\end{enumerate}
\end{document}