Study of the sensitivity of jet parameter distributions to the strong coupling constant $\alpha_{s}$ in $Z^{0} \to e^{+}e^{-}$ events at ATLAS

Due to the large hadronic content in each interaction, leptons are expected to be the primary signature to look for in many processes, hence the importance of reconstructing them efficiently. This thesis presents an algorithm to measure the efficiency of the electron reconstruction software and the expected performance from data. The results show our capacity to evaluate the efficiency at different integrated luminosities over a large kinematic range under different background conditions. We also validate the development of an ATLAS specific simulation framework aimed at fast event processing. In order to achieve this, this thesis compares outputs of the different simulation frameworks, both a full Geant4 simulation and the ATLAS specific fast simulation ATLFASTII. The study compares the distributions in a standard Z0 → e+e− sample and assesses the consistency of different background processes with the event selection cuts. Finally, we use locally produced fast simulation samples to assess the sensitivity to modifications of the strong coupling constant on the number of Z0 → e+e− events associated with additional jets. This sensitivity is compared to the expected experimental uncertainties, such as the choice of jet algorithms, jet energy scales or theoretical uncertainties such as the parton distribution function uncertainty.