Edit and compile if you like:
\documentclass[tikz]{standalone}\tikzset{cross/.style={path picture={\draw[black](path picture bounding box.south east) -- (path picture bounding box.north west)(path picture bounding box.south west) -- (path picture bounding box.north east);}}}\begin{document}\begin{tikzpicture}\draw (-2.25,0) node[left] {$\varphi_a$} -- (2.25,0) node[right] {$\varphi_b$};\draw[->,yshift=5pt] (-2,0) -- (-1,0) node[midway,above] {$p_1$};\draw[->,yshift=5pt] (1,0) -- (2,0) node[midway,above] {$p_2$};\draw[fill=white,cross] (0,0) circle (0.2) node[above=5pt] {$\partial_t R_{k,ab}(p_1,p_2)$};\end{tikzpicture}\end{document}
Click to download: feynman-2.tex
Open in Overleaf: feynman-2.tex
This file is available on tikz.netlify.app and on GitHub and is MIT licensed.
See more on the author page of Janosh Riebesell..