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Using the data on coherent $J/psi$ photoproduction in Pb-Pb ultraperipheral collisions (UPCs) obtained in Runs 1 and 2 at the Large Hadron Collider (LHC), we determined with a good accuracy the nuclear suppression factor of $S_{Pb}(x)$ in a wide range of the momentum fraction $x$, $10^{-5} leq x leq 0.04$. In the small-$x$ region $x < 10^{-3}$, our $chi^2$ fit favors a flat form of $S_{Pb}(x) approx 0.6$ with approximately a 5% accuracy for $x=6 times 10^{-4} - 10^{-3} $ and a 25% error at $x=10^{-4}$. At the same time, uncertainties of the fit do not exclude a slow decrease of $S_{Pb}(x)$ in the small-$x$ limit. At large $x$, $S_{Pb}(x)$ is constrained to better than 10% precision up to $x=0.04$ and is also consistent with the value of $S_{Pb}(x)$ at $langle x rangle =0.042$, which we extract from the Fermilab data on the $A$ dependence of the cross section of coherent $J/psi$ photoproduction on fixed nuclear targets. The resulting uncertainties on $S_{Pb}(x)$ are small, which indicates the potential of the LHC data on coherent charmonium photoproduction in Pb-Pb UPCs to provide additional constraints on small-$x$ nPDFs. We explicitly demonstrate this using as an example the EPPS16 and nCTEQ16 nuclear parton distribution functions, whose uncertainties decrease severalfold after the Bayesian reweighting of the discussed UPC data.
Using the general notion of cross section fluctuations in hadron--nucleus scattering at high energies, we derive an expression for the cross section of incoherent $J/psi$ photoproduction on heavy nuclei $dsigma_{gamma A to J/psi Y}/dt$, which include
Interpreting the J/psi suppression reported in nucleus--nucleus collisions at SPS and RHIC requires the quantitative understanding of cold nuclear matter effects, such as the inelastic rescattering of J/psi states in nuclei or the nuclear modificatio
We study inclusive $J/psi$ photoproduction at NLO at large $P_T$ at HERA and the EIC. Our computation includes NLO QCD leading-$P_T$ corrections, QED contributions via an off-shell photon as well as those from $J/psi$+charm channels. For the latter,
The photoproduction of heavy vector mesons in the electromagnetic interactions of ultra-relativistic nuclei is sensitive to the gluon distribution in the nucleus and thus to cold nuclear matter effects like shadowing or parton saturation. Besides the
Using QCD calculations of the cross section of inclusive dijet photoproduction in Pb-Pb ultraperipheral collisions in the LHC kinematics as pseudo-data, we study the effect of including these data using the Bayesian reweighting technique on nCTEQ15,