B D₀^? and B_s D^?_s0 form factors from QCD light-cone sum rules

We present the first application of QCD light-cone sum rules (LCSRs) with B-(s)-meson distribution amplitudes to the B-(s) -> D-(s)0(& lowast;) form factors, where D-(s)0(& lowast;) is a charmed scalar meson. We consider two scenarios for the D-0(& lowast;) spectrum. In the first one, we follow the Particle Data Group and consider a single broad resonance D-0(& lowast;)(2300). In the second one, we assume the existence of two scalar resonances, D-0(& lowast;)(2105) and D-0(& lowast;)(2451), as follows from a recent theoretically motivated analysis of B D pi pi decays. The B D0 & lowast; form factors are calculated in both scenarios, also taking into account the large total width of D-0(& lowast;)(2300). Furthermore, we calculate the Bs D-s0(& lowast;) form factors, considering in this case only the one-resonance scenario with D-s0(2317). In this LCSRs calculation, the c-quark mass is kept finite and the s-quark mass is taken into account. We also include contributions of the two-and three-particle distribution amplitudes up to twist-four. Our predictions for semileptonic B -> D-0(& lowast;)& ell;nu(& ell;) and B-s -> D-s0(& lowast;)& ell;nu(& ell;) branching ratios are compared with the available data and HQET-based predictions. As a byproduct, we also obtain the D-0(& lowast;)- and D-s0(& lowast;)-meson decay constants and predict the lepton flavour universality ratios R(D-0(& lowast;)) and R(D-s0(& lowast;)).