|Vub | from B →π ν decays and (2+1)-flavor lattice QCD

Jon A. Bailey, A. Bazavov, C. Bernard, C. M. Bouchard, C. DeTar, D. Du, A. X. El-Khadra, J. Foley, E. D. Freeland, E. Gámiz, Steven Gottlieb, U. M. Heller, J. Komijani, A. S. Kronfeld, John W Laiho, L. Levkova, Yuzhi Liu, P. B. Mackenzie, Y. Meurice, E. NeilSi Wei Qiu, J. N. Simone, R. Sugar, D. Toussaint, R. S. Van De Water, R. Zhou

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80 Scopus citations


We present a lattice-QCD calculation of the B→π ν semileptonic form factors and a new determination of the CKM matrix element |Vub|. 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 parametrization 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 |Vub|, we simultaneously fit the experimental data for the B→π ν differential decay rate obtained by the BABAR and Belle collaborations together with our lattice form-factor results. We find |Vub|=(3.72±0.16)×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 |Vub| to the same level as the experimental error. We also provide results for the B→π ν 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.

Original languageEnglish (US)
Article number014024
JournalPhysical Review D
Issue number1
StatePublished - Jul 23 2015


ASJC Scopus subject areas

  • Nuclear and High Energy Physics

Cite this

Bailey, J. A., Bazavov, A., Bernard, C., Bouchard, C. M., DeTar, C., Du, D., El-Khadra, A. X., Foley, J., Freeland, E. D., Gámiz, E., Gottlieb, S., Heller, U. M., Komijani, J., Kronfeld, A. S., Laiho, J. W., Levkova, L., Liu, Y., Mackenzie, P. B., Meurice, Y., ... Zhou, R. (2015). |Vub | from B →π ν decays and (2+1)-flavor lattice QCD. Physical Review D, 92(1), [014024]. https://doi.org/10.1103/PhysRevD.92.014024