Leading twist nuclear shadowing: Uncertainties, comparison to experiments, and higher twist effects

Using the leading twist approach to nuclear shadowing, which is based on the relationship between nuclear shadowing and diffraction on a nucleon, we calculate next-to-leading order nuclear parton distribution functions (nPDFs) and structure functions in the region 0.2 > x > 10^-5 and Q ² ≥ 4 GeV². The uncertainties of our predictions due to the uncertainties of the experimental input and the theory are quantified. We determine the relative role of the small (∼ Q²) and large ( ≫ Q²) diffractive masses in nuclear shadowing as a function of x and find that the large mass contribution, which is an analog of the triple Pomeron exchange, becomes significant only for x ≤ 10^-4. Comparing our predictions to the available fixed-target nuclear deep inelastic scattering data, we argue, based on the current experimental studies of the leading twist diffraction, that the data at moderately small x ∼ 0.01 and Q² ∼ 2 GeV² could contain significant higher twist effects hindering the extraction of nPDFs from that data. Also, we find that the next-to-leading order effects in nuclear shadowing in the ratio of the nucleus to nucleon structure functions F₂ are quite sizable. Within the same formalism, we also present results for the impact parameter dependence of nPDFs. We also address the problem of extracting the neutron F_2n(x, Q²) from the deuteron and proton data. We suggest a simple and nearly model-independent procedure of correcting for nuclear shadowing effects using F₂^A/ F₂^D ratios.