Technique for Setting Limits on the Coupling Constants of the Effective Theory from Electroweak $Z_\gamma$ Production at the Conditions of Run-2 of the ATLAS Experiment

Tests for deviation from the Standard Model (SM) are guided by its apparent incompleteness and by pursuit of creation of a more general theory of elementary particles. We search in this study for manifestations of new physics in an indirect way, through changes in interactions of already known particles due to the effects of physics beyond the SM. The non-SM interactions are referred to as anomalous (or anomalous couplings). Electroweak Zγ production is a process sensitive to anomalous quartic bosonic couplings. The phenomenology we apply, the effective field theory, enables a model-independent representation of the sought-for effects of new physics in the form of parametrization of the SM Lagrangian using higher-dimensional operators. Each such operator is preceded by a coefficient, which has the meaning of the theory’s coupling constants. We present here a technique developed to set 1D limits on the values of these coefficients. This technique makes it possible to set for some operators the expected limits that are more stringent than the currently available ones.