On the Q dependence of Nuclear Structure Functions

The recent high statistics NMC data on the Tin to Carbon structure function ratio seems to indicate, for the first time, a significant Q dependence, especially at small values of Bjorken x, x < 0.05, and Q > 1 GeV. Pure leading twist, perturbative QCD–based predictions, which are consistent with the free nucleon data, yield a fairly flat ratio with little or no Q dependence. In view of this seeming contradiction, we re-examine the applicability of such a perturbative model to nuclear structure functions in such a kinematical regime. We find that the model is consistent with all data, within experimental errors, without any need for introducing additional higher twist contributions. The model correctly reproduces the Q dependence of the Carbon structure function as well. We also critically examine the Q dependence of the corresponding spin dependent structure functions.