Edit and compile if you like:
\documentclass[tikz,svgnames]{standalone}\usetikzlibrary{patterns}\begin{document}\begin{tikzpicture}[very thick,q0/.style={->,DarkBlue,semithick,yshift=5pt,shorten >=5pt,shorten <=5pt},cross/.style={path picture={\draw[black,thick](path picture bounding box.south east) -- (path picture bounding box.north west)(path picture bounding box.south west) -- (path picture bounding box.north east);}}]% Loop\def\radius{1.5}\draw (0,0) circle (\radius);\node[above] (1) at (0,\radius) {$m_1^2$, $\gamma_1^2$};\node[below] (2) at (0,-\radius) {$m_2^2$, $\gamma_2^2$};\draw[q0] (140:0.75*\radius) arc (140:40:0.75*\radius) node[midway,below] {$q_0$};\draw[fill=white,cross,thick] (0,-\radius) circle (4pt);% External lines\filldraw(-2*\radius,0) -- (-\radius,0) circle (2pt) node[below left] {$g$}(\radius,0) circle (2pt) node[below right] {$g$} -- (2*\radius,0);\draw[q0] (-2*\radius,0) -- (-\radius,0) node[midway,above] {$q_0$};\draw[q0] (\radius,0) -- (2*\radius,0) node[midway,above] {$q_0$};\node[xshift=4cm,scale=1.5] at (0,0) {$+$};\begin{scope}[xshift=8cm]% Loop\def\radius{1.5}\draw (0,0) circle (\radius);\node[above=3pt] (1) at (0,\radius) {$m_1^2$, $\gamma_1^2$};\node[below] (2) at (0,-\radius) {$m_2^2$, $\gamma_2^2$};\draw[q0,yshift=-10pt] (220:0.75*\radius) arc (220:320:0.75*\radius) node[midway,above] {$q_0$};
Click to download: diagrams.tex
Open in Overleaf: diagrams.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..