Speaker
Description
Experimental high-energy-physics data is well described by the Standard Model (SM), a modern theory of elementary particles. However, due to the problems of this model, the main goal of modern experiments is to find deviations from the SM (so-called new physics) in order to find out the right way for its extension. It is convenient and prospective to look for anomalous couplings of already known particles, that is indirect search of new physics. These couplings can be parameterized in the Lagrangian with operators of higher dimensions using effective field theory approach. Experimental data provides opportunity to set limits on operators' parameters (Wilson coefficients) in order to constrain the new physics manifestations. It is crucial to develop new methods that can help to set more stringent limits on Wilson coefficients. In this work method of composite anomalous signal is considered. Its main difference from conventional setting limits methodology lies in accounting of anomalous contributions from background processes in addition to the one from the signal process. This technique is tested for anomalous quartic gauge couplings, described by dimension-eight operators, and applied to the $Z(\nu\bar{\nu})\gamma jj$ and $ZZ(\ell\ell\nu\bar{\nu})jj$ productions in conditions of the ATLAS experiment. Possibility to set the limits on Wilson coefficients in a single analysis adding a control region, constructed to estimate the main background ($W(\ell\nu)\gamma jj$ and $WZ(\ell\nu\nu\bar{\nu}) jj$), to the limit-setting procedure is considered. Finally, combination of the limits from two considered processes is probed with and without considered method. Composite anomalous signal allows one to set more stringent limits. The improvement for some coefficients is significant, especially in case of a single channel study.
