Model-independent extraction of form factors and |Vcb| in Bbar --> D ell- nubar_ell with hadronic tagging at BABAR

Using the entire BABAR Upsilon(4S) dataset, the first two-dimensional unbinned angular analysis of the semileptonic decay Bbar --> D ell- nubar_ell is performed, employing hadronic reconstruction of the tag-side B meson from Upsilon(4S) \to B Bbar. Here, ell denotes the light charged leptons e and mu. A novel data-driven signal-background separation procedure with minimal dependence on simulation is developed. This procedure preserves all multidimensional correlations present in the data. The expected sin^2 theta_ell dependence of the differential decay rate in the Standard Model is demonstrated, where theta_ell is the lepton helicity angle. Including input from the latest lattice QCD calculations and previously available experimental data, the underlying form factors are extracted using both model-independent (BGL) and dependent (CLN) methods. Comparisons with lattice calculations show flavor SU(3) symmetry to be a good approximation in the B(s) --> D(s) sector. Using the BGL results, the CKM matrix element |Vcb| = (41.09 +- 1.16) x 10^-3 and the Standard Model prediction of the lepton-flavor universality violation variable R(D) = 0.300 +- 0.004, are extracted. The value of |Vcb| from Bbar --> D ell- nubar_ell tends to be higher than that extracted using Bbar --> D* ell- nubar_ell. The Standard Model R(D) calculation is at a 1.97sigma tension with the latest HFLAV experimental average.