Measurement of photon-induced $ZZ$ production at the ATLAS Experiment using AFP

This thesis presents a measurement of photon-induced $ZZ$ production using proton-proton collision data at a centre-of-mass energy of 13 TeV and with an integrated luminosity of 14.6 fb$^{-1}$, recorded by the ATLAS experiment at the LHC. The scattered protons are detected by the ATLAS Forward Proton (AFP) detector. Only the four muon final state is considered, which is measured by the central ATLAS detector. The observed measured cross-section using a novel data-blinding method is : \begin{equation*} \sigma_{\text{fid.}}^{\text{meas.}} (\text{fb}) =-0.595 \pm 0.250 \text{ (stat.)} \pm 0.283 \text{ (syst.)} \pm 0.014 \text{ (lumi.)} \end{equation*} This measurement is compatible with the SM-only hypothesis and the results are interpreted as an upper-limit on the cross-section for the process, computed to be of $1.967$ fb at the 95% confidence level. The results are also interpreted as an upper-limit on Wilson coefficients of 15 dimension 8 EFT operators. The upper-limits on the EFT Wilson coefficients are given considering the fully simulated proton-elastic component of the operators only and also by using an estimation of their proton dissociative components. The statistical uncertainties remain dominant in this measurement. The AFP-related systematic uncertainties are dominant but are probably overestimated. A tuning of the fast simulation of AFP as well as the implementation of a data-driven proton pile-up overlay is also described.