Theory determination of B¯→D(∗)ℓ-ν¯ form factors at O(1/mc2)

We carry out an analysis of the full set of ten B¯→D(∗) form factors within the framework of the Heavy-Quark Expansion (HQE) to order Oαs,1/mb,1/mc2, both with and without the use of experimental data. This becomes possible due to a recent calculation of these form factors at and beyond the maximal physical recoil using QCD light-cone sum rules, in combination with constraints from lattice QCD, QCD three-point sum rules and unitarity. We find good agreement amongst the various theoretical results, as well as between the theoretical results and the kinematical distributions in B¯→D(∗){e-,μ-}ν¯ measurements. The coefficients entering at the 1/mc2 level are found to be of O(1), indicating convergence of the HQE. The phenomenological implications of our study include an updated exclusive determination of |Vcb| in the HQE, which is compatible with both the exclusive determination using the BGL parametrization and with the inclusive determination. We also revisit predictions for the lepton-flavour universality ratios RD(∗), the τ polarization observables PτD(∗), and the longitudinal polarization fraction FL. Posterior samples for the HQE parameters are provided as ancillary files, allowing for their use in subsequent studies.