\documentclass[border={20pt 20pt 20pt 20pt}]{standalone}
\usepackage{feynmp}
\DeclareGraphicsRule{*}{mps}{*}{} % for being able to read the produced file                             
\begin{document}
\thispagestyle{empty}

\Large

\begin{fmffile}{feyngraph}
    $\Delta m_\mathrm{H}^2$
    = \quad\parbox{100pt}{
    \begin{fmfgraph*}(100,80)
       \fmfleft{i}
       \fmfright{o}
       \fmfv{label=H,l.a=60}{i}
       \fmfv{label=H,l.a=120}{o}
       \fmf{dashes,tension=1}{i,v1} % ,label=H,label.side=left
       \fmf{dashes,tension=1}{v2,o}
       \fmf{fermion,left,tension=0.4,label=t}{v1,v2,v1}
    \end{fmfgraph*}}
    \quad + \quad\parbox{100pt}{
    \begin{fmfgraph*}(100,80)
       \fmfleft{i}
       \fmfright{o}
       \fmftop{m}
       \fmfv{label=H,l.a=60}{i}
       \fmfv{label=H,l.a=120}{o}
       \fmflabel{t}{m}
       \fmf{dashes,tension=1}{i,v1}
       \fmf{dashes,tension=1}{v1,o}
       \fmf{dashes,right,tension=0}{v1,m,v1}
    \end{fmfgraph*}}
    \quad + \quad\ldots
    \end{fmffile}
\end{document}
