Eur. Phys. J. C (2023) 83: 1119
https://doi.org/10.1140/epjc/s10052-023-12292-2

Regular Article - Theoretical Physics

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

Department of Physical Sciences, Indian Institute of Science Education and Research Kolkata, 741246, Mohanpur, India

^a as19rs008@iiserkol.ac.in

Received: 16 June 2023
Accepted: 27 November 2023
Published online: 11 December 2023

Abstract

We investigate 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 and to overcome this 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 using MCMC analysis at $\sqrt{s}=250$ GeV with integrated luminosities of $\mathcal{L}\in \{100{\text{fb}}^{-1},250{\text{fb}}^{-1},1000{\text{fb}}^{-1},3000{\text{fb}}^{-1}\}$ and different sets of systematic errors. We find that using spin-related observables along with cross section in the presence of initial beam polarization significantly improves the bounds on anomalous couplings compared to previous studies.