On the Cancellation of Nuclear Effects in the Valence Region

Deep-inelastic $e\mathrm{/}\mu$ scattering data off targets ranging from deuterium to lead indicate that the nuclear modifications to the structure functions of bound nucleons are minimal in the kinematic region around the peak of the valence quark distributions. An analysis of world measurements of the isoscalar cross-section ratios ${\sigma }^A\mathrm{/}{\sigma }^{{}^2\text{H}}$ in the region of $0.25\le x\le 0.35$ shows a remarkable cancellation across all nuclei, with an average value of $0.9985\pm 0.0022$. We discuss these results and possible interpretations in the context of a microscopic model of nuclear modifications of the structure functions.