1

I am trying to write a two loop Feynman diagram in a particular format (using pdflatex!), basically with a line dividing in half a loop. Unfortunately while the outcome in the image below is almost what I had in mind, the vertical line intersects the loop which makes it look very sloppy. Is there a way to fix this problem? Or, more broadly, is there a better way to realize this diagram?

  \documentclass{article}
    \usepackage{tikz} 
    \usepackage{tikz-feynman} 
    \tikzfeynmanset{compat=1.1.0}
    \begin{document}
                \begin{tikzpicture}[layered layout,baseline]
                \begin{feynman}
                \vertex (a1);
                \vertex[right=2cm of a1] (a2);
                \vertex[above right= 2.12 cm of a2](a3);
                \vertex[below right= 2.12 cm of a2](a4);
                \vertex[below = 1 cm of a3] (a31);
                \vertex[above = 1 cm of a4] (a32);
                \vertex[right=3cm of a2] (a5); 
                \vertex[right=2cm of a5] (a6); 
                \diagram* {
                    (a1) -- [gluon] (a2)
                    (a2) -- [fermion,half left] (a5)
                    (a3) -- [gluon] (a31) -- [fermion] (a32) -- [gluon] (a4)
                    (a5) -- [fermion,half left] (a2)
                    (a5) -- [gluon] (a6)
                };
                \end{feynman}
                \end{tikzpicture}
    \end{document}

enter image description here

1

I would use quarter lefts and not put an arrow on the gluon since it transforms in a real representation.

\documentclass{article}
\usepackage{tikz} 
\usetikzlibrary{positioning}
\usepackage{tikz-feynman} 
\tikzfeynmanset{compat=1.1.0}
\begin{document}
            \begin{tikzpicture}[layered layout,baseline]
            \begin{feynman}
            \vertex (a1);
            \vertex[right=2cm of a1] (a2);
            \vertex[above right= 2.12 cm of a2](a3);
            \vertex[below right= 2.12 cm of a2](a4);
            \vertex[below = 1 cm of a3] (a31);
            \vertex[above = 1 cm of a4] (a32);
            \vertex[right=3cm of a2] (a5); 
            \vertex[right=2cm of a5] (a6); 
            \diagram* {
            (a1) -- [gluon] (a2)
                -- [fermion, quarter left] (a3)
                -- [fermion, quarter left] (a5)
                -- [fermion, quarter left] (a4)
                -- [fermion, quarter left] (a2),
                (a5) -- [gluon] (a6),
                (a3) -- [gluon] (a4)        
            };
            \end{feynman}
            \end{tikzpicture}
\end{document}

enter image description here

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