Comment on form-factor shape and extraction of |Vub| from B → πlν

Thomas Becher; Richard J. Hill

doi:10.1016/j.physletb.2005.11.063

Comment on form-factor shape and extraction of |V_ub| from B → πlν

Thomas Becher, Richard J. Hill

Physics And Astronomy

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190 Scopus citations

Abstract

We point out that current experimental data for partial B→πlν branching fractions reduce the theoretical input required for a precise extraction of |V_ub| to the form-factor normalization at a single value of the pion energy. We show that the heavy-quark expansion provides a bound on the form-factor shape that is orders of magnitude more stringent than conventional unitarity bounds. We find |V_ub|=(3.7±0. 2±0.1)×[0.8/F₊(16 GeV²)]. The first error is from the experimental branching fractions, and the second is a conservative bound on the residual form-factor shape uncertainty, both of which will improve with additional data. Together with current and future lattice determinations of the form-factor normalization this result gives an accurate, model independent determination of |V_ub|. We further extract semileptonic shape observables such as |V_ubF₊(0)|=0.92±0.11±0. 03 and show how these observables can be used to test factorization and to determine low-energy parameters in hadronic B decays.

Original language	English
Pages (from-to)	61-69
Number of pages	9
Journal	Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
Volume	633
Issue number	1
DOIs	https://doi.org/10.1016/j.physletb.2005.11.063
State	Published - Feb 2 2006

Bibliographical note

Funding Information:
We thank A. Kronfeld, H. Quinn and I. Stewart for discussions. We are grateful to the Institute for Nuclear Theory (Seattle, WA) for hospitality where a part of this work was completed. Research supported by the Department of Energy under Grants DE-AC02-76SF00515 and DE-AC02-76CH03000. Fermilab is operated by Universities Research Association Inc., under contract with the US Department of Energy.

Funding

We thank A. Kronfeld, H. Quinn and I. Stewart for discussions. We are grateful to the Institute for Nuclear Theory (Seattle, WA) for hospitality where a part of this work was completed. Research supported by the Department of Energy under Grants DE-AC02-76SF00515 and DE-AC02-76CH03000. Fermilab is operated by Universities Research Association Inc., under contract with the US Department of Energy.

Funders	Funder number
US Department of Energy
Universities Space Research Association
Michigan State University-U.S. Department of Energy (MSU-DOE) Plant Research Laboratory	DE-AC02-76CH03000, DE-AC02-76SF00515

ASJC Scopus subject areas

Nuclear and High Energy Physics

Access to Document

10.1016/j.physletb.2005.11.063

Cite this

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title = "Comment on form-factor shape and extraction of |Vub| from B → πlν",

abstract = "We point out that current experimental data for partial B→πlν branching fractions reduce the theoretical input required for a precise extraction of |Vub| to the form-factor normalization at a single value of the pion energy. We show that the heavy-quark expansion provides a bound on the form-factor shape that is orders of magnitude more stringent than conventional unitarity bounds. We find |Vub|=(3.7±0. 2±0.1)×[0.8/F+(16 GeV2)]. The first error is from the experimental branching fractions, and the second is a conservative bound on the residual form-factor shape uncertainty, both of which will improve with additional data. Together with current and future lattice determinations of the form-factor normalization this result gives an accurate, model independent determination of |Vub|. We further extract semileptonic shape observables such as |VubF+(0)|=0.92±0.11±0. 03 and show how these observables can be used to test factorization and to determine low-energy parameters in hadronic B decays.",

author = "Thomas Becher and Hill, \{Richard J.\}",

note = "Funding Information: We thank A. Kronfeld, H. Quinn and I. Stewart for discussions. We are grateful to the Institute for Nuclear Theory (Seattle, WA) for hospitality where a part of this work was completed. Research supported by the Department of Energy under Grants DE-AC02-76SF00515 and DE-AC02-76CH03000. Fermilab is operated by Universities Research Association Inc., under contract with the US Department of Energy. ",

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AU - Hill, Richard J.

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PY - 2006/2/2

Y1 - 2006/2/2

N2 - We point out that current experimental data for partial B→πlν branching fractions reduce the theoretical input required for a precise extraction of |Vub| to the form-factor normalization at a single value of the pion energy. We show that the heavy-quark expansion provides a bound on the form-factor shape that is orders of magnitude more stringent than conventional unitarity bounds. We find |Vub|=(3.7±0. 2±0.1)×[0.8/F+(16 GeV2)]. The first error is from the experimental branching fractions, and the second is a conservative bound on the residual form-factor shape uncertainty, both of which will improve with additional data. Together with current and future lattice determinations of the form-factor normalization this result gives an accurate, model independent determination of |Vub|. We further extract semileptonic shape observables such as |VubF+(0)|=0.92±0.11±0. 03 and show how these observables can be used to test factorization and to determine low-energy parameters in hadronic B decays.

AB - We point out that current experimental data for partial B→πlν branching fractions reduce the theoretical input required for a precise extraction of |Vub| to the form-factor normalization at a single value of the pion energy. We show that the heavy-quark expansion provides a bound on the form-factor shape that is orders of magnitude more stringent than conventional unitarity bounds. We find |Vub|=(3.7±0. 2±0.1)×[0.8/F+(16 GeV2)]. The first error is from the experimental branching fractions, and the second is a conservative bound on the residual form-factor shape uncertainty, both of which will improve with additional data. Together with current and future lattice determinations of the form-factor normalization this result gives an accurate, model independent determination of |Vub|. We further extract semileptonic shape observables such as |VubF+(0)|=0.92±0.11±0. 03 and show how these observables can be used to test factorization and to determine low-energy parameters in hadronic B decays.

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