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Title: $$B\to\pi\ell\nu$$ semileptonic form factors from unquenched lattice QCD and determination of $$|V_{ub}|$$

We compute the $$B\to\pi\ell\nu$$ semileptonic form factors and update the determination of the CKM matrix element $$|V_{ub}|$$. We use the MILC asqtad ensembles with $$N_f=2+1$$ sea quarks at four different lattice spacings in the range $$a \approx 0.045$$~fm to $0.12$~fm. The lattice form factors are extrapolated to the continuum limit using SU(2) staggered chiral perturbation theory in the hard pion limit, followed by an extrapolation in $q^2$ to the full kinematic range using a functional $z$-parameterization. The extrapolation is combined with the experimental measurements of the partial branching fraction to extract $$|V_{ub}|$$. Our preliminary result is $$|V_{ub}|=(3.72\pm 0.14)\times 10^{-3}$$, where the error reflects both the lattice and experimental uncertainties, which are now on par with each other.
Authors:
;
Publication Date:
OSTI Identifier:
1327265
Report Number(s):
arXiv:1411.6038; FERMILAB-CONF-14-518-T
1329797
DOE Contract Number:
AC02-07CH11359
Resource Type:
Conference
Resource Relation:
Journal Name: PoS; Journal Volume: LATTICE2014; Conference: 32nd International Symposium on Lattice Field Theory, Brookhaven, NY, USA, 06/23-06/28/2014
Research Org:
Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States); Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
Contributing Orgs:
Fermilab Lattice; MILC
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS