To wrap the external lines so that it can touch the perimeter

Similar to this, Wrapping a Feynman diagram in an ellipse or a circle?, I am having some in tikz problem making sure the legs of these diagrams touching the perimeter. I tried the following, but I am not quite able to do it. Will somebody kindly help me draw these kind of diagrams?
\begin{center}
\tikzset{
particle/.style={decorate, draw=black,
    decoration={aspect=0.08,segment length=3pt,amplitude=3pt}}}\begin{tikzpicture}[node distance=1cm and 1.5cm]
\coordinate (e1);\coordinate[below left=of e1] (aux6); \coordinate[below right=of aux6] (aux7); \coordinate[below left=of aux7] (aux8);
\coordinate[below=1cm of aux1] (aux);
\draw[particle] (aux7) -- (aux6); \draw[particle] (aux7) -- (aux8); \draw[particle] (aux7) -- (aux); \draw[particle] (aux7) -- (aux8); \draw[particle] (e1) -- (aux1); \draw[particle] (aux1) -- (e2); \draw[particle] (e3) -- (aux2); \draw[particle] (aux2) -- (e4); \draw[particle] (aux1) -- node {} (aux2); \node[draw,name path=circle,line width=3pt,circle,fit=(e1) (e4) (aux7) (aux8),inner sep=.5\pgflinewidth] {}; %\path[name intersections={of=circle and diameter, by={aux3}}];% find the intersection \draw[particle] (aux) -- (aux3); %\draw[particle] (aux2) -- (aux3); %\draw[particle] (aux3) -- (aux1); \end{tikzpicture} \end{center}