Search for Heavy Boson Resonances in Final States with a W or Z Boson and a Photon Using 139 \fb of Proton-Proton Collision Data at sqrt(s) = 13 TeV Collected with the ATLAS

This thesis presents a search for boson resonances that decay into an energetic photon and the Standard Model's W or Z boson: $X \to W\gamma$ and $X \to Z\gamma$. The dataset used for the measurement was collected at the CERN Large Hadron Collider during a run period from 2015 to 2018. The proton-proton collision center-of-mass energy was 13 TeV with a useful integrated luminosity recorded using the ATLAS detector of 139 \fb. New particle identification techniques are employed, and event selection criteria are optimized to improve the search sensitivity. No significant deviations from the Standard Model predictions are observed over a $W\gamma$ and $Z\gamma$ mass range from 1.0 to 6.8 TeV. The data are used to set limits with 95\% confidence level on the production cross section of massive bosons that are predicted by various extensions of the Standard Model's theory of elementary particles.