Measuring Z boson production in heavy-ion collisions with ALICE, with a view on the upgrade of the experiment

The interest in the phenomenology of relativistic heavy-ion collisions is driven by the many open points about the nature of the strong interaction, as well as by cosmological reasons. The physics of heavy ions is not limited to the study of the hot matter created when they collide (QGP, Quark-Gluon Plasma); the nuclear environment modifies the behaviour of their constituents independently on the subsequent QGP formation. The understanding of such cold nuclear effects constitutes a necessary reference for the correct interpretation of the entire system evolution. Electroweak bosons production is a clean handle for the investigation of such effects, in particular for measuring the modification of the parton distribution functions (PDFs) inside the nucleus. The thesis aims at presenting the activities I carried out within the ALICE Collaboration (LHC, Cern). The core is the measurement of Z boson production in lead-lead collisions at high energy. The usefulness of such research is presented in the first chapter. The results, discussed in chapter 3, show a significant suppression of the Z production because of nuclear shadowing of the PDFs. This is actually the strongest evidence of nuclear shadowing measured by ALICE with gauge bosons. The last chapter, given as appendix, presents the activities I carried out on the assembly and qualification of the new inner tracker system (ITS) of ALICE. ​