Study of anomalous $W^-W^+\gamma/Z$ couplings using polarizations and spin correlations in $e^-e^+\to W^-W^+$ with polarized beams

Abstract

We study the anomalous $W^-W^+\gamma/Z$ couplings in $e^-e^+\to W^-W^+$ followed by semileptonic decay using a complete set of polarization and spin correlation observables of $W$ boson with the longitudinally polarized beam. We consider a complete set of dimension-six operators affecting $W^-W^+\gamma/Z$ vertex, which are $SU(2)\times U(1)$ gauge invariant. Some of the polarization and spin correlation asymmetries average out if the daughter of $W^+$ is not tagged. We developed an artificial neural network and boosted decision trees to distinguish down-type jets from up-type jets. We obtain bounds on the anomalous couplings for center of mass energy $\sqrt{s} = 250$ GeV with integrated luminosities of~$\mathcal{L}\in\{100~\text{fb}^{-1}, 250~\text{fb}^{-1}, 1000~\text{fb}^{-1}, 3000~\text{fb}^{-1}\}$. We find that using spin-related observables and cross~section in the presence of initial beam polarization significantly improves the bounds on anomalous couplings compared to previous studies.