Constraining anomalous gauge boson couplings in $e^+e^-\to W^+W^-$ using polarization asymmetries with polarized beams

Abstract

We study the anomalous $W^+W^-V$ ($V=\gamma,Z$) couplings in $e^+e^-\to W^+W^-$ using the complete set of polarization observables of $W$ boson with longitudinally polarized beams. We use most general Lorentz invariant form factors parametrization as well as $SU(2)\times U(1)$ invariant dimension $6$ effective operators for the effective $W^+W^-V$ couplings. We estimate simultaneous limits on the anomalous couplings in both the parametrizations using cross section, forward backward asymmetry and polarization observables of $W$ boson with different kinematical cuts using Markov-Chain--Monte-Carlo (MCMC) method for an $e^+e^-$ collider running at centre of mass energy of $\sqrt{s}=500$ GeV and ${\cal L}=100$ fb$^{-1}$. The best limits on form factors are obtained to be $1 \sim 5 \times 10^{-2}$ for $e^-$ and $e^+$ polarization being $(+0.4,-0.4)$. For operator's coefficients, the best limits are obtained to be $1\sim 16$ TeV$^{-2}$.