Première mesure de section efficace de production du boson W et de son asymétrie de charge avec l’expérience ATLAS.

The ATLAS detector is a multi-purpose experiment located at one of the collision points of the LHC, at CERN. The detector is complete and acquiring data since June 2008. The commissioning of the calorimeter system has been possible since then, in particular through the study of the "missing transverse energy" variable. This variable is essential for precision measurements of the Standard Model, and for the search of New Physics ; it was then tested in situ for the first time. The detector was ready for the first LHC collisions at the end of 2009, and showed good performances, in particular when created by minimum bias events. With the collision data, it was also possible to study the electron performances, in particular the identification variables and the material before the calorimeter. The first collisions at 7 TeV centre-of-mass energy allowed to study the properties of W bosons. After a few month of data taking, this particle was observed and the production cross-section was measured. The main issue of this study was the assessment of the systematic uncertainties due to the electron and to the missing transverse energy. With all the data recorded in 2010, the W boson charge asymmetry was also measured. This measurement is important for the determination of the parton distribution functions of the proton, which are of utmost importance for the understanding of hadronic collisions at the LHC.