Prospects for observing the $η_{t}$ ${\to}$ $W^{+}W^{-}$ decay at the HL-LHC

Abstract

Motivated by the recent observation of the pseudoscalar toponium $η_{t}$ at the LHC and by the ongoing interest in its properties, we phenomenologically investigate the $η_{t}$ ${\to}$ $W^{+}W^{-}$ process, one of the characteristic decays of toponium $η_{t}$. The branching ratio for the $η_{t}$ ${\to}$ $W^{+}W^{-}$ decay is estimated with two scenarios of the decay constant $f_{η_{t}}$. It is found that tens of dilepton events from the cascade decays, $η_{t}$ ${\to}$ $W^{+}W^{-}$ ${\to}$ ${\ell}^{-}\barν_{\ell}{\ell}^{{\prime}+}ν_{{\ell}^{\prime}}$ with ${\ell}$, ${\ell}^{\prime}$ $=$ $e$ and $μ$, could be experimentally observed, when considering the realistic identification efficiency of the charged lepton and assuming more than $3{\times}10^{7}$ $η_{t}$ events available at the future HL-LHC. We propose searching for $η_{t}$ via the $η_{t}$ ${\to}$ $W^{+}W^{-}$ ${\to}$ ${\ell}^{-}\barν_{\ell}{\ell}^{{\prime}+}ν_{{\ell}^{\prime}}$ channel, which features no $b$-jets and clean dilepton signatures, thus offering a complementary and potentially more sensitive probe.