Coherence effects in scattering order expansion of light by atomic   clouds
  We interpret cooperative scattering by a collection of cold atoms as a multiple scattering process. Starting from microscopic equations describing the response of $N$ atoms to a probe light beam, we represent the total scattered field as an infinite series of multiple scattering events. As an application of the method, we obtain analytical expressions of the coherent intensity in the double scattering approximation for Gaussian density profiles. In particular, we quantify the contributions of coherent backward and forward scattering. 
Mohamed-Taha Rouabah, Marina Samoylova, Romain Bachelard, Philippe W.   Courteille, Robin Kaiser and Nicola Piovella
physics.optics physics.atom-ph quant-ph