Probing anomalous quartic gauge couplings in same-sign $W$ boson scattering with polarization and spin correlation

Abstract: The study of quartic couplings of electroweak gauge bosons not only provides a test of the Standard Model (SM) predictions, but also can look for signals of new physics beyond the SM. We present a comprehensive study of anomalous quartic gauge couplings in same-sign $W^\pm W^\pm$ production via vector boson scattering at the LHC. The analysis is carried out within the framework of the SM Effective Field Theory, exploiting polarization and spin-correlation effects encoded in angular asymmetries in addition to conventional kinematic observables. We demonstrate that spin-correlation asymmetries provide sensitivity to anomalous $WWWW$ interactions that is comparable to that obtained from the transverse mass distribution of the $WW$ system. By identifying a minimal set of the most sensitive asymmetries, we show that the dominant constraints on the Wilson coefficients can be captured with a reduced number of observables. A combined analysis of angular asymmetries and kinematic information leads to improved limits compared to either approach alone. The impact of unitarity considerations is also examined by imposing invariant-mass cut-offs on the $WW$ system, allowing us to determine unitarity-safe regions for the anomalous couplings.