Study of the Wtb vertex structure at the ATLAS experiment

The top quark is the heaviest and least studied quark of the Standard Model. Although its properties have already been investigated at colliders, the statistics of the collected data have not yet allowed for precise measurements, with exception of its mass. The determination of other fundamental properties such as its couplings requires larger top quark samples, which will be available at the Large Hadron Collider (LHC) at CERN. Within the Standard Model, the Wtb vertex is purely left-handed, and its amplitude is given by the Cabibbo-Kobayashi-Maskawa matrix element Vtb, related to weak interaction between a top and a b-quark. In a more general way, additional anomalous couplings such as right-handed vectorial couplings and left and right-handed tensorial couplings can also be considered. The study of the angular distribution of the top quark decay products at the LHC will allow precision measurements of the structure of the Wtb vertex, providing also an important probe for possible physics beyond the SM. In the present thesis, the ATLAS sensitivity to anomalous Wtb couplings is studied. For this, the t anti-t pair production at the LHC is considered and different observables, such as angular asymmetries and W helicity fractions and ratios, are discussed. The expected results for luminosities of 10/fb and 1/fb are obtained through the combination of the most sensitive observables.