# Tikz-Feynman: massless two point function at two loops

I would like to write on Latex the following Feynman diagrams involving a massless two point function at two loops

I am using Tikz-Feynman but I am new on it and for the moment I can only write the code for three level diagrams. Thanks in advance for any suggestion.

• Welcome to TeX.SX! Please help us (and also you) and add a minimal working example (MWE), that illustrates your problem. It will be much easier if we see compilable code, starting with \documentclass and ending with \end{document}. – Bobyandbob Oct 7 '17 at 14:36

Here is a suggestion for a basic definition of four node styles that mimic your image.

The output shown below is from pdflatex, with lualatex the positioning was a bit off.

\documentclass[border=5mm]{standalone}
\usepackage{tikz-feynman}
\tikzset{
Sbase/.style={
circle,
draw,
minimum size=8mm, % increased from 3mm
/tikz/graphs/as={},
},
SA/.style={
Sbase,
path picture={
\draw (path picture bounding box.west) -- (path picture bounding box.east);
},
label={[yshift=-height("#1")]center:#1}
},
SB/.style={
Sbase,
path picture={
\draw (path picture bounding box.west) to[bend right=45] (path picture bounding box.north);
},
label={center:#1}
},
SC/.style={
Sbase,
path picture={
\draw (path picture bounding box.150) to[bend right=20] (path picture bounding box.30);
},
label={center:#1}
},
SD/.style={
Sbase,
path picture={
\draw (path picture bounding box.south) -- (path picture bounding box.north);
},
label={[xshift=width("#1")]center:#1}
},
SA/.default={},
SB/.default={},
SC/.default={},
SD/.default={},
}
\begin{document}
\feynmandiagram{
a[SA=1] -- b[SB=2] -- c[SC=3] -- d[SD=4]
};
\end{document}

• Really thanks Torbjorn, at this point I would like to add momentum line on the internal loop. I was thinking to add them as [momentum] near -- , but this only gives momenta on the two external legs. How can I define them inside the loop? Thanks in advance for your time – Andrea.Phys Oct 8 '17 at 8:50
• @Andrea.Phys I suggest you ask a new question about that, and do include a complete code example in that. (I know basically nothing about Feynman diagrams, and have absolutely no idea what loop you're talking about.) – Torbjørn T. Oct 8 '17 at 9:39
• Without talking of loops, I only need to assign a visible number to every line in a diagram. The problem is that I can only assign number on straight lines, while I can't assign any number to the lines inside the circles, do you have any suggestion? – Andrea.Phys Oct 8 '17 at 9:45
• @Andrea.Phys I updated, was that something like what you had in mind? – Torbjørn T. Oct 8 '17 at 9:57
• No, I need to assign a number to every single line in the diagram, where for line I mean a line that starts into a vertex and ends into another one. In this sense I would have to assign to the first circle 3 independet numbers, while for the last one 4 independet ones. – Andrea.Phys Oct 8 '17 at 10:02