Probing anomalous top-Higgs couplings at the HL-LHC via Hto WW^(ast) decay channels

We study the prospects of probing the anomalous $tHq$~($q= u, c$) couplings via SS2L or 3L signatures at the High Luminosity (HL-LHC) run of the 14 TeV CERN collider. We focus on signals of the $tH$ associated production followed by the decay modes $t\to b\ell^{+}\nu_{\ell}$ and $H\to WW^{\ast}$, and $t\bar{t}$ production followed by the decay modes $t\to b\ell^{+}\nu_{\ell}$ and $\bar{t}\to H(\to WW^{\ast})\bar{q}$, where $\ell=e, \mu$. Based on two types of $H\to WW^{\ast}$ decay topologies, one assuming the semileptonic decay mode $H\to WW^{\ast}\to \ell^{+}\nu jj $ and the other the fully leptonic decay mode $H\to WW^{\ast}\to \ell^{+}\nu \ell^{-}\bar{\nu}$, we perform a full simulation for signals and backgrounds. It is shown that, at the future HL-LHC, the branching ratio $Br(t\to uh)~(Br(t\to ch))$ can be probed to $1.17~(1.56)\times 10^{-3}$ for the same-sign di-lepton channel and to $7.1~\times 10^{-4}~(1.39~\times 10^{-3})$ for the 3L channel at $3\sigma$ sensitivity.