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