Search for intrinsic charm in the proton at the ATLAS experiment

The dynamics of strong interactions and the internal content of the proton have been a matter of interest for particle physics ever since the discovery of quarks. This thesis focuses on the analysis of processes involving heavy quarks in the final states and, in particular, on a phenomenon called intrinsic charm, which is a model that predicts the existence of charm quarks in the initial state of the proton. The study of charm quarks relies on heavy flavour b- and c-jets, which can be produced in hadronic collisions. The work was done in the context of the Z+heavy flavour group, one of the groups performing precise measurements in the ATLAS experiment of the cross section of the production of the Z boson. In particular, the focus was on developing predictions for Z+b-jets in a particular calculation scheme with massive quarks (called 4 Flavour Number Scheme), on intrinsic charm sensitivity optimization and intrinsic charm predictions. A second part of the thesis involved Parton Density Function parameterization, with a focus on an innovative Machine Learning technique called symbolic regression.