The nucleon structure function $F_2^N$ computed in a holographic framework can be used to describe nuclear deep inelastic scattering effects provided that a rescaling of the $Q^2$ momentum and of the IR hard-wall parameter $z_0$ is made. The ratios $R_A=F_2^A/F_2^N$ can be obtained in terms of a single rescaling parameter $λ_A$ for each nucleus. The resulting ratios agree with experiment in a wide range of the shadowing region.
We generalize the leading twist theory of nuclear shadowing and calculate quark and gluon generalized parton distributions (GPDs) of spinless nuclei. We predict very large nuclear shadowing for nuclear GPDs. In the limit of the purely transverse momentum transfer, our nuclear GPDs become impact-parameter-dependent nuclear parton distributions (PDFs). Nuclear shadowing induces nontrivial correlations between the impact parameter b and the light-cone fraction x. We make predictions for the deeply virtual Compton scattering (DVCS) amplitude and the DVCS cross section on Pb-208 at high energies. W…
The leading twist theory of nuclear shadowing predicts the shadowing correction to nuclear parton distributions at small $x$ by connecting it to the leading twist hard diffraction in electron-nucleon scattering. The uncertainties of the predictions are related to the shadowing effects resulting from the interaction of the hard probe with $N \ge 3$ nucleons. We argue that the pattern of hard diffraction observed at HERA allows one to reduce these uncertainties. We develop a new approach to the treatment of these multiple interactions, which is based on the concept of the color fluctuations and …
Nuclear shadowing corrections to the structure functions of deep inelastic scattering of intermediate-mass nuclei are calculated at very low values of Bjorken x and small values of Q^2 (Q^2<5 GeV^2). The two-component approach (generalized VMD plus hard pomeron) is used for a description of the underlying virtual photon - nucleon interaction. The hard component of the nucleon structure function is calculated in a framework of the colour dipole model with dipole cross section having Regge-type energy dependence. Numerical results for nuclear shadowing corrections are compared with available dat…
While current nuclear parton distribution functions (nPDFs) from global fits to experimental data are spatially homogeneous, many experimental observables in nucleus-nucleus collisions are presented in terms of centrality cuts. These cuts can be related to impact parameter using the Glauber theory and it is thus usual in the description of such observables to convolute an assumed impact parameter distribution with the homogeneous nPDFs. In this study we use the Gribov theory of nuclear shadowing supplemented with information from diffraction to model the impact parameter distributions of nucle…
The quarkonium hadroproduction in association with a photon at high energies provides a probe of the dynamics of the strong interactions as it is dependent on the nuclear gluon distribution. Therefore, it could be used to constrain the behavior of the nuclear gluon distribution in proton-nucleus and nucleus-nucleus collisions. Such processes are useful to single out the magnitude of the shadowing/antishadowing effects in the nuclear parton densities. In this work we investigate the influence of nuclear effects in the production of JPsi + photon and Upsilon + photon and estimate the transverse …
Nuclear shadowing corrections to the structure functions of deep inelastic scattering on intermediate-mass nuclei are calculated at very small values of Bjorken x and small values of Q^2 (Q^2<5 Gev^2). The two-component approach developed in previous works of authors for a description of the nucleon structure functions of deep inelastic scattering is used. It is shown that the hard component of the nucleon structure functions that arises, in terms of the colour dipole model, from qq-pairs with a high transverse momentum, is almost not shadowed. It is shown that a change of the slope of the sha…
We show that the recent ALICE measurements of exclusive J/ψ production in ultraperipheral PbPb collisions at 2.76 TeV provide the first direct experimental evidence for the strong nuclear gluon shadowing in lead at $x \sim 10^{-3}$. The evidence is based on the comparison of the nuclear suppression factor S(x\approx 0.001)=0.61^{+0.05}_{-0.04} found in the analysis of the coherent J/ψ photoproduction cross sections measured by ALICE with the nuclear gluon shadowing predicted by the global fits of nuclear parton distributions and by the leading twist theory of nuclear shadowing.
Integrated and differential $J/ψ R_{AA}$ are systematically studied in Au-Au collisions at RHIC-BES energies in a transport approach, including cold and hot nuclear effects respectively in the initial condition and the collision terms. With decreasing energy, while the temperature, life time and size of the QGP fireball decrease, the nuclear absorption of the initially produced charmonia is more and more strong, and the nuclear shadowing effect on charmonium regeneration goes to anti-shadowing first and then to shadowing again. As a competition between the cold and hot nuclear effects, the QGP…
