Inclusive and Diffractive Dijet Photoproduction in Ultraperipheral Pb-Pb Collisions at the LHC

In this contribution, we summarize NLO pQCD predictions for inclusive anddiffractive dijet photoproduction in Pb-Pb UPCs at the LHC. We demonstrate thatthe theory describes well the preliminary ATLAS data on the inclusive crosssection, which probes nuclear parton distributions (PDFs) down to x_A ≈0.005 and which can reduce current uncertainties of the small-x nucleargluon distribution by approximately a factor of 2. Employing predictions of theleading twist approach to nuclear shadowing for nuclear diffractive PDFs, wecalculate the cross section of diffractive dijet photoproduction and show thatits x_γ dependence is sensitive to the effect of nuclear shadowing andthe mechanism of QCD factorization breaking in hard diffraction. We also findthat due to large leading twist nuclear shadowing and restricted kinematics,the diffractive contribution to the inclusive cross section of dijetphotoproduction does not exceed 5-10interpretation of the ATLAS data.