|Vub| from B→πℓν decays and (2+1)-flavor lattice QCD
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AuthorBailey, J. A.; Gámiz Sánchez, María Elvira; Fermilab Lattice Collaboration; MILC Collaboration
American Physical Society
Bailey, J., Bazavov, A., Bernard, C., Bouchard, C. M., DeTar, C., Du, D., ... & Gottlieb, S. (2015). | Vub| from B→ πℓν decays and (2+ 1)-flavor lattice QCD. Physical Review D, 92(1). [https://doi.org/10.1103/PhysRevD.92.014024]
SponsorshipNational Institute for Computational Science; Pittsburgh Supercomputer Center; San Diego Supercomputer Center; Texas Advanced Computing Center; National Science Foundation's Teragrid/XSEDE Program; United States Department of Energy (DOE) DE-FG02-91ER40628 DE-FC02-12ER41879 DE-SC0010120 DE-FG02-91ER40661 DE-FC02-06ER41443 DE-FG02-13ER42001 DE-FG02-13ER41976 DE-SC0010114 DE-AC02-98CH10886 DE-AC02-07CH11359; National Science Foundation (NSF) PHY-1067881 PHY-10034278 PHY-1417805 PHY1212389 PHY-1316748; URA Visiting Scholars' program; MINECO (Spain) FPA2010-16696 FPA2006-05294; Spanish Government; Junta de Andalucia FQM-101 FQM-6552; European Commission Joint Research Centre PCIG10-GA-2011-303781; German Excellence Initiative; European Union (EU) 291763; European Union (EU); Basic Science Research Program of the National Research Foundation of Korea (NRF); Ministry of Education 2014027937; Creative Research Initiatives Program of the NRF grant - Korean government (MEST) 2014001852
We present a lattice-QCD calculation of the B→πℓν 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→πℓν 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→πℓν 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.