Adding Channels Containing Hadronically Decaying Taus to Multilepton EFT Analysis

This thesis presents a search for new physics impacting associated top quark production using the EFT framework. Six different processes were considered ttll, ttlnu, ttH, tttt, tllq, and tHq. The analysis targets the leptontic signature of these processes, requiring the selected events to have two, three, or four leptons. In this version of the analysis, hadronically decaying taus were included in the requirements for the event selection. The potential new physics effects are parameterized in terms of 26 dimension-six EFT operators. The events for this analysis are subcategorized in terms of kinematic distributions. The predicted distribution in each category is compared to the experimentally observed distribution of proton-proton collision data collected by the CMS experiment from 2016 to 2018, totaling 138 fb-1. The confidence intervals for the EFT parameters are extracted with a likelihood scan of the 26 EFT parameters. The results of the analysis are consistent with the standard model predictions, but the improvements made in this version of the analysis were able to place further constraints on the theoretical models of new physics.