Drawing disconnected diagram with tikz-feynman

Question

I am trying to draw a disconnected diagram which consists of two propagators, however one of the propagators has a cactus loop. I have this code so far

\begin{center}
\feynmandiagram [horizontal = a to b] {
    a -- b [dot]
    -- [out = 135, in = 45, loop, min distance = 2cm] b -- c,
    d -- e,
    {[edges={draw=none}]
        a -- d, c -- e,
    },          
};
\end{center}

However the output is very strange and looks like this

My question is, how do I make this diagram pretty where all the lines are horizontal? Also, How do I make the cactus loop line on top?

Answer 1

Something like this is it your drawing using tikz-feynman? I have added a MWE that works with LuaLaTeX.

\documentclass[12pt]{article}
\usepackage[compat=1.1.0]{tikz-feynman}

\begin{document}
\begin{center}
\feynmandiagram [horizontal=a to b, layered layout] {
  a -- b [dot] -- [out =135, in=45, loop, min distance=2cm] b -- c,
};
\end{center}
\end{document}

Follow-up: You can use the node of TikZ package to put "an horizontal line propagator on top with a loop, and then another horizontal line propagator with no loop below". With the coordinates (0, 0.5) and (0, -0.5) you can increase the distance between the loop and the horizontal line that I have set with medium. Peraphs there are many improvements or hacks or tricks to get your request.

\documentclass[12pt]{article}
\usepackage[compat=1.1.0]{tikz-feynman}
\usepackage{tikz}
\begin{document}
\begin{center}
\begin{tikzpicture}
\node at (0, 0.5) {\feynmandiagram [horizontal=a to b, layered layout] {
  a -- b [dot] -- [out =135, in=45, loop, min distance=2cm] b -- c,
};};
\node at (0, -0.5) {\feynmandiagram [medium, horizontal=d to e, layered layout] {d -- [plain] e}; };
\end{tikzpicture}
\end{center}
\end{document}