\mathcal{L}={1\over 2}\partial^\mu \phi_a \partial_\mu \phi_a -{m^2\over 2}\phi_a \phi_a +{1\over 2}F^2-{\sqrt{\lambda /N}\over 2}F \phi_a \phi_a .
At least perturbatively, the dominant contribution to the 2k-point connected correlation function is of the order (1/N)k-1 and the other terms are higher powers of 1/N.