On the $Q^2$ dependence of nuclear structure functions

Abstract

The recent high statistics NMC data on the Tin to Carbon structure function ratio seems to indicate, for the first time, a significant Q 2 dependence, especially at small values of Bjorken x, x < 0.05, and Q 2 > 1 GeV2. A purely log(Q 2)-type dependence of the structure functions, which is consistent with the free nucleon data, yields a fairly flat ratio with little or no Q 2 dependence. In view of this seeming contradiction, we re-examine the applicability of such a 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 Q 2 dependences or higher twist contributions. The model correctly reproduces the Q 2 dependence of the Carbon structure function as well. We also critically examine the Q 2 dependence of the corresponding spin dependent structure functions.