Measurement of the \(W^{\pm}Z\) Production Cross Section and Limits on Anomalous Triple Gauge Couplings at \(\sqrt s = 7 TeV\) using the ATLAS detector

Abstract

This dissertation presents a measurement of the (W^{\pm}Z) production cross section and limits on anomalous triple gauge couplings in proton-proton collisions at a center of mass energy of 7 TeV using data produced by LHC collisions and acquired by the ATLAS detector in 2011. The measurement and limits probe the electroweak sector of the Standard Model at high energies and allow for generic tests for new physics that could be present at high energy scales. This analysis is also useful for understanding the ATLAS detector response in the presence of multi-lepton signatures. The dataset used corresponds to an integrated luminosity of (1.02 fb^{−1}). The measurement relies on the leptonic decay modes of the W and Z, resulting in final states with electrons, muons, and missing energy. Events are selected by requiring three high momentum leptons, a large missing transverse energy, a Z candidate (reconstructed from two of the leptons) with a mass consistent with the Z pole mass, and a W candidate (reconstructed from the third lepton and the missing energy) with a large transverse mass. The backgrounds to the (W^{\pm}Z) process are estimated using Monte Carlo simulations and Data-Driven techniques. A total of 71 (W^{\pm}Z) candidate events are observed in data, with 50.3 signal and 12.1 background events expected. The production cross section is extracted from these events using a maximum likelihood method, and is found to be in good agreement with the Standard Model expectation. Limits at the 95% confidence interval on anomalous triple gauge couplings are extracted from the observed event yields using a frequentist limit setting approach.