Gluon saturation is an emergent phenomenon in QCD at high energy and for large nuclei. Although predicted by QCD perturbation theory and indirectly confirmed by a variety of data (from electron-proton collisions at HERA to proton-nucleus and nucleus-nucleus collisions at the LHC), this phenomenon has never been directly observed. This internship (that could be followed by a PhD thesis) proposes to explore a new class of observables, like di-jet production in electron-nucleus or proton-nucleus collisions, which are sensitive to gluon saturation via the correlations between the produced particles. These observables will be measured in the future experiments at the Large Hadron Collider (LHC, CERN) and the Electron-Ion Collider (EIC, USA).