$B \to D^{(*)}\ell\nu$ form factors from $N_f\!=\!2+1$ QCD with M\"obius domain-wall quarks

We report on our study of the B \to D^(*) \ell \nu semileptonic decays at zero and nonzero recoils in 2+1 flavor QCD. The Mobius domain-wall action is employed for light, charm and bottom quarks at lattice cutoffs 1/a = 2.5 and 3.6 GeV. We take bottom quark masses up to \approx 2.4 times the physical charm mass to control discretization effects. The pion mass is as low as M_\pi \sim 310 MeV. We present our preliminary results for the relevant form factors and discuss the violation of heavy quark symmetry, which is a recent important isuue on the long-standing tension in the Cabibbo-Kobayashi-Maskawa matrix element |V_{cb}| between the exclusive and inclusive decays.