Measurements of the Differential Charged-Current Drell-Yan Cross-Section and Muon Charge Asymmetry at High Transverse Masses with the ATLAS Detector

This thesis presents the measurements of the $W \rightarrow \mu \nu$ charged-current Drell-Yan process, utilising the experimental data recorded by the ATLAS experiment during the $\mathrm{Run-2}$ period of $pp$ collisions at the LHC at $13~\mathrm{TeV}$, corresponding to a total integrated luminosity of $139~\mathrm{fb}^{-1}$. The measurements are performed differentially in the transverse mass of the $\mathrm{W}$ boson, $m_{\mathrm{T}}^{\mathrm{W}}$, focusing on the high mass tail ranging from $200~\mathrm{GeV}$ to $2000~\mathrm{GeV}$. In this region, the statistical uncertainty dominates, with the systematic uncertainty originating from the muon sagitta bias correction being a significant contributor. Specifically, for $W^+$ bosons, the muon sagitta bias correction reaches up to around $8\%$, while for $W^-$ bosons, it reaches up to around $15\%$, with a maximum of around $33\%$ for the muon charge asymmetry. Notably, in the highest $m_{\mathrm{T}}^{\mathrm{W}}$ bin, the statistical uncertainty exceeds the systematic uncertainty, reaching up to around $40\%$ for the muon charge asymmetry. When compared to the theoretical predictions of POWHEG-BOX and PYTHIA8 at the born level of the signal, the results show a good agreement between the theory and measurements.