# Operator matrix element Feynman diagrams

I am trying to draw the following cutted diagram

but I don't know how to do it.

I am using feynmf for the Feynman diagrams for my thesis since tikz-feynman requires lualatex and it gives enormous compiling times.

On a more general note, I would like to know these Wick contraction diagrams are usually made

As far as I know, there isn't any specific package to do them beside tikz which is a bit cumbersome and I really would like to avoid it!

• My regards from Sicily :-)...Please can I know where you have taken the first image? Where have you taken the images type1,2,3,4? From an old book? Aug 26, 2021 at 11:56
• @Sebastiano Ciao! The first diagram I draw it myself with a tablet. The others come from a recent work on $\epsilon^\prime/\epsilon$, but they are well known in the literature and can be found in many other places. These were the ones I had at hand at the moment! Aug 26, 2021 at 12:07
• I hope I am not mistaken but I have seen the pdf. Whoever wrote the article also uses typical Word fonts (i.e. Symbol). It may be that the article is not written in LaTeX. Also, the images are inserted externally and may not be created with a specific package. I have some doubt, but I think they were created with a graphics program. Grazie very very much. :-) Aug 26, 2021 at 12:25
• @Sebastiano Yes, I would imagine that the images are possibly made externally to latex. But if we take, for example, the diagrams in pages 51/52 of this lectures they seem to be directly done in latex! Aug 26, 2021 at 13:00
• @Sebastiano The paper is (badly) written in TeX (you can download the source) but the figures are external, generated by cairo (maybe gnuplot? the arrow heads look familiar...). Aug 26, 2021 at 14:42

I haven't used feynmf/feynmp in ages, so this is unfortunately all I can offer:

\documentclass{article}

\usepackage{feynmp-auto}

\begin{document}

\begin{fmffile}{diagram}
\begin{fmfgraph*}(100,50)
\fmfstraight
\fmfleft{k,o} \fmflabel{$K^+$}{k}
% po=neutral pion; pm= help point for phantom line; pz=useless;pp=charged pion
\fmfright{po,pm,pz,pp}\fmflabel{$\pi^0$}{po}\fmflabel{$\pi^+$}{pp}
\fmftop{t}% help vertex
\fmf{plain,right=.2}{k,po}
\fmf{plain,left=.2}{k,v2,po}
\fmf{phantom}{t,v2}
\fmffreeze
\fmf{plain,right=.6,tension=.5}{pp,v1,pp}
\fmf{dashes,left=.3}{v2,v1}
\fmf{phantom,tension=.6}{o,vl}\fmf{plain,tension=2,left=.1,fore=red}{vl,vr}\fmf{phantom}{vr,pm}
\end{fmfgraph*}
\end{fmffile}

\end{document}


• Well this seems quite good to be honest! I'll wait for, possibly, other answers to come which might be more general. But thank you very much! Aug 26, 2021 at 11:00
• I like me...your code...In fact I like feynmp package :-))) I think that those diagrams are made with pstricks (bezier curves). Looking closely at the second image with all those diagrams it looks like they are not specific to a package that relates to Feynmann diagrams. +1 Aug 26, 2021 at 11:54