The $B \to D \ell \nu$ form factors at nonzero recoil and $|V_{cb}|$ from $2+1$-flavor lattice QCD
| Autor: | Lattice, Fermilab, Collaborations, MILC, Bailey, Jon A., Bazavov, A., Bernard, C., Bouchard, C. M., DeTar, C., Du, Daping, El-Khadra, A. X., Foley, J., Freeland, E. D., Gámiz, E., Gottlieb, Steven, Heller, U. M., Komijani, J., Kronfeld, A. S., Laiho, J., Levkova, L., Mackenzie, P. B., Neil, E. T., Qiu, Si-Wei, Simone, J., Sugar, R., Toussaint, D., Van de Water, R. S., Zhou, Ran |
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| Rok vydání: | 2015 |
| Předmět: | |
| Zdroj: | Phys. Rev. D 92, 034506 (2015) |
| Druh dokumentu: | Working Paper |
| DOI: | 10.1103/PhysRevD.92.034506 |
| Popis: | We present the first unquenched lattice-QCD calculation of the hadronic form factors for the exclusive decay $\overline{B} \rightarrow D \ell \overline{\nu}$ at nonzero recoil. We carry out numerical simulations on fourteen ensembles of gauge-field configurations generated with 2+1 flavors of asqtad-improved staggered sea quarks. The ensembles encompass a wide range of lattice spacings (approximately 0.045 to 0.12 fm) and ratios of light (up and down) to strange sea-quark masses ranging from 0.05 to 0.4. For the $b$ and $c$ valence quarks we use improved Wilson fermions with the Fermilab interpretation, while for the light valence quarks we use asqtad-improved staggered fermions. We extrapolate our results to the physical point using rooted staggered heavy-light meson chiral perturbation theory. We then parameterize the form factors and extend them to the full kinematic range using model-independent functions based on analyticity and unitarity. We present our final results for $f_+(q^2)$ and $f_0(q^2)$, including statistical and systematic errors, as coefficients of a series in the variable $z$ and the covariance matrix between these coefficients. We then fit the lattice form-factor data jointly with the experimentally measured differential decay rate from BaBar to determine the CKM matrix element, $|V_{cb}|=(39.6 \pm 1.7_{\rm QCD+exp} \pm 0.2_{\rm QED})\times 10^{-3}$. As a byproduct of the joint fit we obtain the form factors with improved precision at large recoil. Finally, we use them to update our calculation of the ratio $R(D)$ in the Standard Model, which yields $R(D) = 0.299(11)$. Comment: 47 pages, 32 figures |
| Databáze: | arXiv |
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