Measurements of W boson properties at $\sqrt{s}=5$ and 13~TeV with the ATLAS detector at the LHC

This thesis presents measurements of W boson properties at center-of-mass energies of $\sqrt{s}=5$ and 13~TeV with special low-pile-up data-set recorded by the ATLAS detector at the LHC. Thanks to an optimal reconstruction of missing transverse momentum, such data have particular importance for precision measurements of W-boson production. Dedicated detector calibration corrections are introduced first in this document, including the reconstruction and energy calibration of the hadronic recoil, the momentum calibration and selection efficiency of leptons. Besides, a new shower-shape reweighting algorithm optimizes the identification electrons with the electromagnetic calorimeter. The thesis describes the selection the W boson signal and devotes specific attention to the evaluation of backgrounds, presenting in particular a new method for the data-driven estimation of backgrounds from multi-jet production. Based on these studies and theoretical predictions, the W-boson transverse momentum distribution and production cross-sections are measured with high precision at two center-of-mass energies. Preliminary studies of the application of these data to the measurement of the W-boson mass are also presented.