Probing the limits on anomalous quartic gauge couplings via $ZZ\gamma$ production in the $\ell\ell\nu\nu\gamma$ channel at FCC-hh

Abstract

In this study, the sensitivity to anomalous quartic gauge couplings (aQGCs) is projected via $pp \rightarrow ZZ\gamma$ production in the 100 TeV proton-proton Future Circular Collider - hadron-hadron (FCC-hh) for an integrated luminosity of 30 ab$^{-1}$. The $\ell\ell\nu\nu\gamma$ final state under consideration consists of a same-flavor, opposite-sign lepton pair (electrons or muons) from one $Z$ boson, the invisible decay of the other $Z$ boson into neutrinos, and an accompanying photon. The FCC-hh detector response and its effects on the reconstructed objects are included through a realistic detector simulation. Three multivariate techniques are employed to separate the signal from the relevant SM backgrounds. Unitarity is preserved by a strict, operator-dependent bound on the total transverse mass ($M_T^{tot}$) of the system. The median expected significances are calculated within the Asimov approximation for one anomalous coupling varied at a time and for background systematic uncertainties between 0\% and 10\%. The highest separation power is obtained with the deep neural network method. The resulting 95\% confidence level limits on $|f_{T0}/\Lambda^{4}|$, $|f_{T8}/\Lambda^{4}|$, $|f_{T9}/\Lambda^{4}|$ and $|f_{M2}/\Lambda^{4}|$ in the combined $e+\mu$ channel without systematic uncertainties are $2.83\times 10^{-3}$, $1.65\times 10^{-3}$, $3.81\times 10^{-3}$ and $8.97\times 10^{-3}$ TeV$^{-4}$, respectively. We have an order of magnitude improvement when compared to current LHC limits with the assumption of 5\% systematic uncertainty.