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B -> [pi]lv and Bs -> Klv form factors and Vub from 2+1- avor lattice QCD with domain-wall light quarks and relativistic heavy quarks

B -> [pi]lv and Bs -> Klv form factors and Vub from 2+1- avor lattice QCD with domain-wall light quarks and relativistic heavy quarks
B -> [pi]lv and Bs -> Klv form factors and Vub from 2+1- avor lattice QCD with domain-wall light quarks and relativistic heavy quarks
We calculate the form factors for B → πlν   and Bs → Klν decay in dynamical lattice quantum chromodynamics (QCD) using domain-wall light quarks and relativistic b-quarks. We use the (2+1)-flavor gauge-field ensembles generated by the RBC and UKQCD collaborations with the domain-wall fermion action and Iwasaki gauge action. For the b-quarks we use the anisotropic clover action with a relativistic heavy-quark interpretation. We analyze data at two lattice spacings of a ~ 0.11, 0.086 fm with unitary pion masses as light as Mπ ~ 290 MeV. We simultaneously extrapolate our numerical results to the physical light-quark masses and to the continuum and interpolate in the pion/kaon energy using SU(2) “hard-pion” chiral perturbation theory for heavy-light meson form factors. We provide complete systematic error budgets for the vector and scalar form factors f+(q2) and f0(q2) for both B → πlν and BsKlν at three momenta that span the q2 range accessible in our numerical simulations. Next we extrapolate these results to q2=0 using a model-independent z-parametrization based on analyticity and unitarity. We present our final results for f+(q2) and f0(q2) as the coefficients of the series in z and the matrix of correlations between them; this provides a parametrization of the form factors valid over the entire allowed kinematic range. Our results agree with other three-flavor lattice-QCD determinations using staggered light quarks, and have comparable precision, thereby providing important independent cross-checks. Both B → πlν and BsKlν decays enable determinations of the Cabibbo-Kobayashi-Maskawa matrix element |Vub|. To illustrate this, we perform a combined z-fit of our numerical B →  πlν form-factor data with the experimental measurements of the branching fraction from BABAR and Belle leaving the relative normalization as a free parameter; we obtain |Vub| = 3.61(32) × 10-3, where the error includes statistical and all systematic uncertainties. The same approach can be applied to the decay BsKlν to provide an alternative determination of |Vub| once the process has been measured experimentally. Finally, in anticipation of future experimental measurements, we make predictions for B → πlν and BsKlν differential branching fractions and forward-backward asymmetries in the Standard Model.
1-38
Flynn, J.
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Izubuchi, T.
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Lehner, C.
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Soni, A.
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Van de Water, R.S.
c324be76-98ed-485d-a37a-33d1fc9a131d
Witzel, O.
ecd73780-db26-4863-9072-43cfc78a7a12
Flynn, J.
d8e90963-ba56-415c-bbd4-496b7d91d343
Izubuchi, T.
4ee5b26a-e913-4a6b-8a2f-80159b3219b2
Lehner, C.
f5ed25c1-68c1-4a5f-9e01-73233639caae
Soni, A.
7a4196ff-0f6b-429e-af54-d1036e9c433b
Van de Water, R.S.
c324be76-98ed-485d-a37a-33d1fc9a131d
Witzel, O.
ecd73780-db26-4863-9072-43cfc78a7a12

Flynn, J., Izubuchi, T., Lehner, C., Soni, A., Van de Water, R.S. and Witzel, O. (2015) B -> [pi]lv and Bs -> Klv form factors and Vub from 2+1- avor lattice QCD with domain-wall light quarks and relativistic heavy quarks. Physical Review, 91 (74510), 1-38. (doi:10.1103/PhysRevD.91.074510).

Record type: Article

Abstract

We calculate the form factors for B → πlν   and Bs → Klν decay in dynamical lattice quantum chromodynamics (QCD) using domain-wall light quarks and relativistic b-quarks. We use the (2+1)-flavor gauge-field ensembles generated by the RBC and UKQCD collaborations with the domain-wall fermion action and Iwasaki gauge action. For the b-quarks we use the anisotropic clover action with a relativistic heavy-quark interpretation. We analyze data at two lattice spacings of a ~ 0.11, 0.086 fm with unitary pion masses as light as Mπ ~ 290 MeV. We simultaneously extrapolate our numerical results to the physical light-quark masses and to the continuum and interpolate in the pion/kaon energy using SU(2) “hard-pion” chiral perturbation theory for heavy-light meson form factors. We provide complete systematic error budgets for the vector and scalar form factors f+(q2) and f0(q2) for both B → πlν and BsKlν at three momenta that span the q2 range accessible in our numerical simulations. Next we extrapolate these results to q2=0 using a model-independent z-parametrization based on analyticity and unitarity. We present our final results for f+(q2) and f0(q2) as the coefficients of the series in z and the matrix of correlations between them; this provides a parametrization of the form factors valid over the entire allowed kinematic range. Our results agree with other three-flavor lattice-QCD determinations using staggered light quarks, and have comparable precision, thereby providing important independent cross-checks. Both B → πlν and BsKlν decays enable determinations of the Cabibbo-Kobayashi-Maskawa matrix element |Vub|. To illustrate this, we perform a combined z-fit of our numerical B →  πlν form-factor data with the experimental measurements of the branching fraction from BABAR and Belle leaving the relative normalization as a free parameter; we obtain |Vub| = 3.61(32) × 10-3, where the error includes statistical and all systematic uncertainties. The same approach can be applied to the decay BsKlν to provide an alternative determination of |Vub| once the process has been measured experimentally. Finally, in anticipation of future experimental measurements, we make predictions for B → πlν and BsKlν differential branching fractions and forward-backward asymmetries in the Standard Model.

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Accepted/In Press date: 14 April 2015
Published date: 15 April 2015
Organisations: Theoretical Partical Physics Group

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Local EPrints ID: 401308
URI: https://eprints.soton.ac.uk/id/eprint/401308
PURE UUID: 97a6a376-a260-4a42-8143-ac622d2b242a
ORCID for J. Flynn: ORCID iD orcid.org/0000-0002-6280-1677

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Date deposited: 11 Oct 2016 15:47
Last modified: 20 Jul 2019 01:21

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Contributors

Author: J. Flynn ORCID iD
Author: T. Izubuchi
Author: C. Lehner
Author: A. Soni
Author: R.S. Van de Water
Author: O. Witzel

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