Orateur
Description
Inclusive photoproduction of dijets in ultra-peripheral nucleus-nucleus collisions (UPCs) has been suggested as a new probe for studying the nuclear parton distributions (nPDFs). In this talk, we present new NLO pQCD predictions for the photoproduction of dijets in PbPb UPCs at 5.02 TeV with up-to-date nPDFs and realistic impact-parameter dependent photon flux obtained through the nuclear form factor, taking for the first time into account also the modelling of the forward-neutron event class required in the experimental measurements. We show that the presence of high-pT jets biases the cross section at forward dijet rapidities to be dominated by events with relatively small impact parameters between the nuclei, of the order of few nuclear radii. This leads to a sensitivity to the transverse-plane collision geometry, which we then take properly into account by including effects from the finite extent of both the photon-emitting and the target nucleus. We further discuss the potential sensitivity to the spatial dependence of nPDFs in connection to this finding.
