Methodology of accounting for aQGC effect on background for improvement of the limits on EFT coupling constants in case of electroweak $Z\gamma$ production at the conditions of Run2 at the ATLAS experiment

In this report the model-independent effective field theory phenomenology is used to parameterize the anomalous couplings in the Lagrangian with higher-dimensional operators. Setting limits on the operator’s coefficients (EFT coupling constants) leads to new physics constraints. The decomposition technique of MC event generator MG5_aMC is used to produce events corresponding separate terms of the full amplitude. In the classical version of setting these limits, all background processes are considered as non-depending on coefficients. However in general case one or several backgrounds can be affected by non-zero EFT coupling constants. This report presents the way of accounting such background impact in limits setting. As an example the electroweak Zγ production is considered, since this process is extremely sensitive to anomalous quartic gauge couplings. As a result the limits on the EFT coefficients fT0 and fM0 were obtained with accounting of the possible new physics in the electroweakWγ production background, which are 1% and 5% tighter respectively than classical ones.