B_s → Kℓν form factors from lattice QCD with domain-wall heavy quarks

We report on our on-going study of the B_s → Kℓν decay in N_f=2+1 lattice QCD. We employ fully relativistic setup in which the Möbius domain-wall action is used for all quark flavors. The lattice cutoff is a^-1∼ 2.5 GeV, where we take bottom quark masses up to m_Q<0.7a^-1 in order to control discretization errors. We present preliminary results for the relevant form factors extracted from correlator ratios by inspecting their ground state saturation.