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First time posting questions on this specific forum. I am trying to draw a Feynman diagram for the process in which a fermion-antifermion pair annihilate at vertex v1 and a fermion-antifermion pair is created a vertex v2 through an instantaneous Coulomb interaction, using the package feynmf. However, when I use the following

\begin{fmfgraph*}(150,80)
    \fmftop{o1,o2}
    \fmfbottom{i1,i2}
    \fmf{fermion}{i1,v1,o2}
    \fmf{fermion}{o1,v2,i2}
    \fmf{ghost}{v1,v2}
\end{fmfgraph*}

the vertical line for the Coulomb doesn't show up.

feynmf

Can anyone tell me what I am doing wrong?

Thanks.

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  • 1
    Welcome to the TeX.SE: What is the minimal compilable code of your work?
    – Sebastiano
    Oct 29, 2022 at 20:04

1 Answer 1

2

Like this?

\documentclass[a4paper,12pt]{article}

\usepackage{feynmp-auto}

\begin{document}
\begin{fmffile}{ghost}
\begin{fmfgraph*}(150,80)
\fmfleft{i1,i2}
\fmfright{o1,o2}
\fmf{fermion}{i1,v1,o1}
\fmf{fermion}{o2,v2,i2}
\fmf{ghost}{v1,v2}
\fmfdot{v1,v2}
\end{fmfgraph*}
\end{fmffile}
\end{document}

enter image description here

Version of the user @Thruston \fmf{fermion}{i2,v2,o2} instead of \fmf{fermion}{o2,v2,i2}.

\documentclass[a4paper,12pt]{article}

\usepackage{feynmp-auto}

\begin{document}
\begin{fmffile}{ghost}
\begin{fmfgraph*}(150,80)
\fmfleft{i1,i2}
\fmfright{o1,o2}
\fmf{fermion}{i1,v1,o1}
\fmf{fermion}{i2,v2,o2}
\fmf{ghost}{v1,v2}
\fmfdot{v1,v2}
\end{fmfgraph*}
\end{fmffile}
\end{document}

enter image description here

Addendum: without the dots.

\documentclass[a4paper,12pt]{article}

\usepackage{feynmp-auto}

\begin{document}
\begin{fmffile}{ghost}
\begin{fmfgraph*}(150,80)
\fmfleft{i1,i2}
\fmfright{o1,o2}
\fmf{fermion}{i1,v1,o1}
\fmf{fermion}{i2,v2,o2}
\fmf{ghost}{v1,v2}
\end{fmfgraph*}
\end{fmffile}
\end{document}

enter image description here

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  • 1
    Hi, thanks for your answers. I actually need the diagram I posted above, but with the left and right parts separated by a vertical dashed line.
    – Christian
    Oct 29, 2022 at 21:22
  • then change \fmf{fermion}{o2,v2,i2} to \fmf{fermion}{i2,v2,o2}...
    – Thruston
    Oct 29, 2022 at 22:27

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