On the range of validity of the parton model

Abstract

Based on the world DIS data we extract $F_2^p-F_2^n$ as a function of Bjorken $x$ and photon virtuality $Q^2$. The standard PDFs fail to describe the experimental data below $Q^2<$ 7 GeV${}^2$. The trend of the data is approximately explained by our recent model.

Comments: 2 pages, LaTeX with 1 eps figure, a talk at DIS2000, Liverpool