A simple model for NN correlations in quasielastic lepton-nucleus   scattering
  We present a covariant extension of the relativistic Fermi gas model which incorporates correlation effects in nuclei. Within this model, inspired by the BCS descriptions of systems of fermions, we obtain the nuclear spectral function and from it the superscaling function for use in treating high-energy quasielastic electroweak processes. Interestingly, this model has the capability to yield the asymmetric tail seen in the experimental scaling function. 
M.B. Barbaro, R. Cenni, T.W. Donnelly, A. Molinari