Thesis

The standard model of particle physics has so far provided a fine description of experimental data, notably data from colliders such as the LHC at CERN. The electroweak sector is of particular interest, notably because of its connections with the Higgs sector and because it is described by a certain number of parameters, of which in reality only three are independent: measuring these parameters precisely makes it possible to check the consistency of the whole.
A good probe for these studies is the neutral current Drell–Yan process (NCDY: production of a pair of charged leptons in hadronic collisions, via the exchange of a Z boson or a virtual photon). This process makes it possible, among other things, to measure the mass of the Z boson, its width, or the electroweak mixing angle sin²?_W. The goal of this thesis is to focus on this latter parameter, and in particular on its value at high energy, by measuring the cross section of the NCDY process at high mass, in the two-muon channel. The most precise measurement in this energy regime is expected, thanks to the large amount of data accumulated by the ATLAS experiment during Run 3 (2022–2026), which can be combined with Run 2 (2015–2018), although more than twice smaller.