$|V_{ub}|$ from $B\to\pi\ell\nu$ decays and (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., Liu, Yuzhi, Mackenzie, P. B., Meurice, Y., 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, 014024 (2015) |
| Druh dokumentu: | Working Paper |
| DOI: | 10.1103/PhysRevD.92.014024 |
| Popis: | We present a lattice-QCD calculation of the $B\to\pi\ell\nu$ semileptonic form factors and a new determination of the CKM matrix element $|V_{ub}|$. We use the MILC asqtad 2+1-flavor lattice configurations at four lattice spacings and light-quark masses down to 1/20 of the physical strange-quark mass. We extrapolate the lattice form factors to the continuum using staggered chiral perturbation theory in the hard-pion and SU(2) limits. We employ a model-independent $z$ parameterization to extrapolate our lattice form factors from large-recoil momentum to the full kinematic range. We introduce a new functional method to propagate information from the chiral-continuum extrapolation to the $z$ expansion. We present our results together with a complete systematic error budget, including a covariance matrix to enable the combination of our form factors with other lattice-QCD and experimental results. To obtain $|V_{ub}|$, we simultaneously fit the experimental data for the $B\to\pi\ell\nu$ differential decay rate obtained by the BaBar and Belle collaborations together with our lattice form-factor results. We find $|V_{ub}|=(3.72\pm 0.16)\times 10^{-3}$ where the error is from the combined fit to lattice plus experiments and includes all sources of uncertainty. Our form-factor results bring the QCD error on $|V_{ub}|$ to the same level as the experimental error. We also provide results for the $B\to\pi\ell\nu$ vector and scalar form factors obtained from the combined lattice and experiment fit, which are more precisely-determined than from our lattice-QCD calculation alone. These results can be used in other phenomenological applications and to test other approaches to QCD. Comment: 63 pages, 48 figures; v2: minor changes in Sec. IV, Table X, modified Fig.14,16, results unchanged |
| Databáze: | arXiv |
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