Nuclear Deep Inelastic Scattering around $x=0.3$

Deep-inelastic scattering (DIS) data on nuclei, from deuterium to lead, indicate that nuclear effects on the partonic structure of bound nucleons are remarkably small around $x=0.3$, where valence-quark distributions peak. We present the results of a global analysis of DIS data on the cross-section ratios ${\sigma }^A\mathrm{/}{\sigma }^{{}^2\text{H}}$ in the range $0.25\le x\le 0.35$, revealing a remarkable cancellation of nuclear effects across the entire range of nuclear targets. We also discuss the interpretation of such an observation within a microscopic model of nuclear modifications of the structure functions.