Theory determination of $$\varvec{\bar{B}\rightarrow D^{(*)}\ell ^-\bar{\nu }}$$ B¯→D(∗)ℓ-ν¯ form factors at $$\varvec{\mathcal {O}(1/m_c^2)}$$ O(1/mc2)

oleh: Marzia Bordone, Martin Jung, Danny van Dyk

Format: Article
Diterbitkan: SpringerOpen 2020-01-01

Deskripsi

Abstract We carry out an analysis of the full set of ten $$\bar{B}\rightarrow D^{(*)}$$ B¯→D(∗) form factors within the framework of the Heavy-Quark Expansion (HQE) to order $$\mathcal {O}\left( \alpha _s,\,1/m_b,\,1/m_c^2\right) $$ 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 $$\bar{B}\rightarrow D^{(*)}\lbrace e^-,\mu ^-\rbrace \bar{\nu }$$ B¯→D(∗){e-,μ-}ν¯ measurements. The coefficients entering at the $$1/m_c^2$$ 1/mc2 level are found to be of $$\mathcal {O}(1)$$ O(1) , indicating convergence of the HQE. The phenomenological implications of our study include an updated exclusive determination of $$|V_{cb}|$$ |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 $$R_{D^{(*)}}$$ RD(∗) , the $$\tau $$ τ polarization observables $$P_\tau ^{D^{(*)}}$$ PτD(∗) , and the longitudinal polarization fraction $$F_L$$ FL . Posterior samples for the HQE parameters are provided as ancillary files, allowing for their use in subsequent studies.