Observables and moments of cooperative resonance fluorescence

The moments of the fluorescent radiation of a $J^2$-invariant, cooperative fluorescent group of atoms are calculated exactly. Both photon bunching and antibunching can occur in the fluorescent radiation. All finite-order moments have a critical-point behavior at ${\Omega }_c=J\gamma$ in the cooperative limit of $J\to \infty$. The maximum normalized intensity correlation is 6/5 which shows greatly reduced intensity fluctuations compared to noncooperative resonance fluorescence. Enhanced antibunching in all the fluorescent correlation functions occurs in the threshold region.