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Published August 30, 2019 | Published
Journal Article Open

Extraction of form Factors from a Four-Dimensional Angular Analysis of B̅→D∗ℓ−ν_ℓ


An angular analysis of the decay B̅→D∗ℓ−ν_ℓ, ℓ∈{e,μ}, is reported using the full e^+e^− collision data set collected by the BABAR experiment at the Υ(4S) resonance. One B meson from the Υ(4S)→BB̅ decay is fully reconstructed in a hadronic decay mode, which constrains the kinematics and provides a determination of the neutrino momentum vector. The kinematics of the semileptonic decay is described by the dilepton mass squared, q^2, and three angles. The first unbinned fit to the full four-dimensional decay rate in the standard model is performed in the so-called Boyd-Grinstein-Lebed approach, which employs a generic q^2 parametrization of the underlying form factors based on crossing symmetry, analyticity, and QCD dispersion relations for the amplitudes. A fit using the more model-dependent Caprini-Lellouch-Neubert (CLN) approach is performed as well. Our form factor shapes show deviations from previous fits based on the CLN parametrization. The latest form factors also provide an updated prediction for the branching fraction ratio R(D∗) ≡ B(B̅→D∗τ−ν_τ)/B(B̅→D∗ℓ−ν_ℓ) = 0.253±0.005. Finally, using the well-measured branching fraction for the B̅→D∗ℓ−ν_ℓ decay, a value of |V_(cb)| = (38.36±0.90)×10^(-3) is obtained that is consistent with the current world average for exclusive B̅→D(*)ℓ−ν_ℓ decays and remains in tension with the determination from inclusive semileptonic B decays to final states with charm.

Additional Information

© 2019 Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP3. Received 26 March 2019; revised manuscript received 30 June 2019; published 29 August 2019. We are grateful for the excellent luminosity and machine conditions provided by our PEP-II colleagues, and for the substantial dedicated effort from the computing organizations that support BABAR. The collaborating institutions thank SLAC for its support and kind hospitality. This work is supported by DOE and NSF (USA), NSERC (Canada), CEA and CNRS-IN2P3 (France), BMBF and DFG (Germany), INFN (Italy), FOM (Netherlands), NFR (Norway), MES (Russia), MINECO (Spain), STFC (United Kingdom), and BSF (USA-Israel). Individuals have received support from the Marie Curie EIF (European Union) and the A. P. Sloan Foundation (USA).

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Published - PhysRevLett.123.091801.pdf


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