A Search for Anomalous Gauge Couplings in Triple Massive Vector Boson Production with a Hadronic Tau in the Final State

This thesis presents a search for anomalous gauge couplings in the electroweak sector in the production of three massive vector bosons (W and Z). The analysis targets final states involving a tau decaying to two quarks (a hadronic tau). The results of the search are analyzed within the framework of standard model effective field theory. 12 Wilson coefficients (WCs) at mass dimension 6 and 20 WCs at mass dimension 8 are considered. Observed data from 138 fb-1 of vs = 13 TeV proton-proton collision events recorded by the CMS detector at the LHC is compared against standard model background predictions from Monte Carlo simulation. The observed yields are found to be consistent with the standard model prediction for triple massive vector boson production. These results are used to derive 95% confidence intervals for each WC under consideration. The limits placed depend upon the sensitivity of the analysis final states to the various WCs. The three WCs to which this analysis has the greatest sensitivity are cW , cHq3, and cHq1 for which 95% confidence limits [-0.25, 0.24] TeV-2 , [-0.47, 0.43] TeV-2, and [-0.61, 0.72] TeV-2 respectively are determined.