Counting the number of correlated pairs in a nucleus
  We suggest that the number of correlated nucleon pairs in an arbitrary nucleus can be estimated by counting the number of proton-neutron, proton-proton, and neutron-neutron pairs residing in a relative $S$ state. We present numerical calculations of those amounts for the nuclei $^{4}$He, $^{9}$Be, $ ^{12}$C, $ ^{27}$Al, $ ^{40}$Ca, $ ^{48}$Ca, $ ^{56}$Fe, $ ^{63}$Cu, $ ^{108}$Ag, and $ ^{197}$Au. The results are used to predict the values of the ratios of the per-nucleon electron-nucleus inelastic scattering cross section to the deuteron in the kinematic regime where correlations dominate. 
Maarten Vanhalst, Wim Cosyn, Jan Ryckebusch
nucl-th