Form factors for B(Bc)→Dlv in light-cone sum rules with chiral current correlator

In this paper we calculate the weak form factors of the decays B(B-c) -> Dl (nu) over bar by using the chiral current correlator within the framework of the QCD light-cone sum rules (LCSR). The expressions of the form factors only depend on the leading twist distribution amplitude (DA) of the D meson. Three models of the D-meson distribution amplitude are employed and the calculated form factors,F-B -> D(0) and F-Bc -> D(0) are given. In the velocity transfer region 1.14 < y < 1.59, which renders the Operator Product Expansion (OPE) near light-cone x(2) = 0 to go effectively, the yielding behavior of form factor is in agreement with that extracted from the data on B -> Dl (nu) over bar, within the error. In the large recoil region 1.35 < y < 1.59, the form factor F-B -> D(0) is observed consistent with that of perturbative QCD (pQCD). The presented calculation can play a bridge role connecting those from the lattice QCD, heavy quark symmetry and pQCD to have an all-around understanding of B -> Dl (nu) over bar transitions. Our prediction for F-Bc -> D(0), by using the D-meson distribution amplitude with the exponential suppression at the end points, is compatible with other approaches, and favors the three-points sum rules (3PSR) approach with the Coulumb corrections.