Momentum Dependent Vertices $\sigma \gamma \gamma$, $\sigma \rho \gamma$   and $\sigma \rho \rho$ : The NJL Scalar Hidden by Chiral Symmetry
  We calculate the momentum dependence of three particle vertices $\sigma \gamma \gamma$, $\sigma \rho \gamma$ and $\sigma \rho \rho$ in the context of a Nambu Jona Lasinio type model. We show how they influence the processes $\gamma \gamma \rightarrow \sigma \rightarrow \pi \pi$, $\rho \rightarrow \gamma \sigma$ and $\gamma \gamma \rightarrow \rho \rho$ and how chiral symmetry shadows the presence of the $\sigma$. 
B. Bajc, A.H. Blin, B. Hiller, M.C. Nemes and M. Rosina