OBSERVATION OF THE W->TAUNU PROCESS IN THE ATLAS EXPERIMENT

The ATLAS Experiment is a multi-purpose detector, operating at the LHC. In this thesis the first observation of W → τν decays in ATLAS with proton-proton collisions at 7 TeV centre-of-mass energy is presented. The amount of data used corresponds to an integrated luminosity of 2.46±0.27 pb^(−1). The W → τν decays are searched in the channel in which the tau decays into a neutrino and a hadronic system.