Measurement of the W boson charge asymmetry in proton-proton collisions at $\sqrt{s}$ = 8 TeV and developments towards the upgrade of the ATLAS Muon Spectrometer

The measurement of the W boson production cross-section in proton proton collisions at the Large Hadron Collider (LHC) provides an excellent probe of the structure functions of the proton. In this thesis, a first measurement of this production cross-section in the muon decay channel at a center of mass energy of 8 TeV with the ATLAS detector is presented. Special attention is drawn to the resulting charge asymmetry, which has been derived as a function of the muon pseudorapidity. This constrains significantly the u and d quark momentum fractions in the proton, thus providing an important input for several high precision measurements, conducted at the LHC. The overall muon charge asymmetry from the W boson yields $\textrm{A}_{\mu} = 0.18392 \pm 0.00146 (\textrm{syst.})$, which is the most precise measurement at the LHC using one single decay channel. In order to allow for similar high precision measurements during the high luminosity phase of the LHC after 2020, the muon system of the ATLAS detector has to be upgraded, especially for the forward region of the muon detector. Therefore prototype detectors for this upgrade project had been developed, constructed and tested. Results of the construction process and the relevant performance studies are also presented here.