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

Abstract

Listen

Translate article

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 $0.2>x>{10}^{\ensuremath{-}5}$ and ${Q}^{2}\ensuremath{\ge}4\text{ }\text{ }{\mathrm{G}\mathrm{e}\mathrm{V}}^{2}$. 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 ($\ensuremath{\sim}{Q}^{2}$) and large ($\ensuremath{\gg}{Q}^{2}$) 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 $x\ensuremath{\le}{10}^{\ensuremath{-}4}$. 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 $x\ensuremath{\sim}0.01$ and ${Q}^{2}\ensuremath{\sim}2\text{ }\text{ }{\mathrm{G}\mathrm{e}\mathrm{V}}^{2}$ 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 ${F}_{2}$ 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 ${F}_{2n}(x,{Q}^{2})$ from the deuteron and proton data. We suggest a simple and nearly model-independent procedure of correcting for nuclear shadowing effects using ${F}_{2}^{A}/{F}_{2}^{D}$ ratios.