A Search for Top Quark Flavor Changing Neutral Currents in Multilepton Final States Using an Effective Field Theory Framework

This thesis presents a search for top quark involved flavor changing neutral currents (FCNCs) within the context of an effective field theory (EFT). Parameterizing potential new physics effects in terms of 6 dimension-six EFT operators, two FCNC processes are studied. The analysis targets the leptonic signatures of these processes, requiring the selected events to contain three leptons. The predicted distribution is compared to the experimentally observed distribution, using 41.48 fb$^{-1}$ of proton-proton collision data collected by the CMS experiment in 2017. A boosted decision tree classifier is trained to separate background from signal. A likelihood fit of the 6 EFT parameters to the observed data is performed to extract the one and two standard deviation confidence intervals for the EFT parameters. While the results are consistent with the standard model prediction, the extracted limits can help to constrain theoretical models of new physics; interpreted in terms of the energy scale probed by the experiment, the results can also provide information about the energy frontier with the hope of finding new physics beyond.