Gluon Saturation from DIS to Nucleus-Nucleus Collisions

In this series of three lectures, I discuss several aspects of high energy scattering among hadrons in Quantum Chromodynamics. The first lecture is devoted to a presentation of gluon saturation and of the Color Glass Condensate (CGC). The second lecture describes the application of this framework to Deep Inelastic Scattering and to proton-nucleus collisions. In the third lecture, we present the application of the CGC to the study of high energy hadronic collisions, with emphasis on nucleus-nucleus collisions. In particular, we provide the outline of a proof of high energy factorization for inclusive gluon production. (author)