\documentclass[tikz]{standalone}
\usepackage{tikz-feynman}

\begin{document}
	\footnotesize
\begin{tikzpicture}[dot/.style={draw,shape=circle,fill=black}]
	\begin{feynman}
		\vertex (u1) {$u$};
		\vertex [below=1cm of u1] (s1) {$s$};
		\vertex at ($(u1)+(2,-3)$) (g11);
		\vertex at ($(s1)+(2,-3)$) (g12);
		\vertex [right=of g11, dot] (g21);
		\vertex [right=of g12, dot] (g22);
		\vertex at ($(g21)+(2,3)$) (u2) {$u$};
		\vertex at ($(g22)+(2,3)$) (s2) {$s$};
		\vertex at ($(g12)+(.5,-2)$) (s3) {$s$};
		\vertex at ($(g22)-(.5,2)$) (s4) {$s$};
		
		\diagram  {
			(u1) -- [fermion] (g11) -- [fermion] (g21) -- [fermion] (u2),
			(g11) -- [gluon,edge label=$g$] (g12), 	(g21) -- [gluon,edge label'=$g$] (g22),
			(s3) -- [fermion] (g12) -- [fermion] (s1),
			(s2) -- [fermion] (g22) -- [fermion] (s4),
		};
		
		\draw [decoration={brace,mirror}, decorate] (u1.north west) -- node [left] {$\kappa^-$} (s1.south west);
		\draw [decoration={brace}, decorate] (u2.north east) -- node [right] {$\kappa^+$} (s2.south east);
		\draw [decoration={brace,mirror}, decorate] (s3.south west) -- node [below] {$\phi$} (s4.south east);
		
		\node [dot,scale=.5] at (g11) {};
		\node [dot,scale=.5] at (g12) {};
		\node [dot,scale=.5] at (g21) {};
		\node [dot,scale=.5] at (g22) {};

	\end{feynman}
\end{tikzpicture}
\end{document}