Exclusive semileptonic Bs→Kℓν decays on the lattice
Exclusive semileptonic Bs→Kℓν decays on the lattice
Semileptonic Bs→Kℓν decays provide an alternative b-decay channel to determine the Cabibbo-Kobayashi-Maskawa (CKM) matrix element |Vub| and to obtain a R-ratio to investigate lepton-flavor-universality violations. Results for the CKM matrix element may also shed light on the discrepancies seen between analyses of inclusive or exclusive decays. We calculate the decay form factors using lattice QCD with domain-wall light quarks and a relativistic b-quark. We analyze data at three lattice spacings with unitary pion masses down to 268 MeV. Our numerical results are interpolated/extrapolated to physical quark masses and to the continuum to obtain the vector and scalar form factors f+(q2) and f0(q2) with full error budgets at q2 values spanning the range accessible in our simulations. We provide a possible explanation of tensions found between results for the form factor from different lattice collaborations. Model- and truncation-independent z-parametrization fits following a recently proposed Bayesian-inference approach extend our results to the entire allowed kinematic range. Our results can be combined with experimental measurements of Bs→Ds and Bs→K semileptonic decays to determine |Vub|=3.8(6)×10−3. The error is currently dominated by experiment. We compute differential branching fractions and two types of R ratios, the one commonly used as well as a variant better suited to test lepton-flavor universality.
hep-lat, hep-ph
Flynn, Jonathan M.
d8e90963-ba56-415c-bbd4-496b7d91d343
Hill, Ryan C.
32648a2c-42f6-4433-866e-0d40767ee601
Jüttner, Andreas
a90ff7c5-ae8f-4c8e-9679-b5a95b2a6247
Soni, Amarjit
1d4d3e39-9bc6-4861-8ced-fca957e79dfa
Tsang, J. Tobias
e4648385-cecf-4c02-b13e-c06312f16b12
Witzel, Oliver
ceb5d2c8-8f0a-46f4-977e-7d45c6b06b82
16 June 2023
Flynn, Jonathan M.
d8e90963-ba56-415c-bbd4-496b7d91d343
Hill, Ryan C.
32648a2c-42f6-4433-866e-0d40767ee601
Jüttner, Andreas
a90ff7c5-ae8f-4c8e-9679-b5a95b2a6247
Soni, Amarjit
1d4d3e39-9bc6-4861-8ced-fca957e79dfa
Tsang, J. Tobias
e4648385-cecf-4c02-b13e-c06312f16b12
Witzel, Oliver
ceb5d2c8-8f0a-46f4-977e-7d45c6b06b82
Flynn, Jonathan M., Hill, Ryan C., Jüttner, Andreas, Soni, Amarjit, Tsang, J. Tobias and Witzel, Oliver
(2023)
Exclusive semileptonic Bs→Kℓν decays on the lattice.
Physical Review D, 107 (11), [114512].
(doi:10.1103/PhysRevD.107.114512).
Abstract
Semileptonic Bs→Kℓν decays provide an alternative b-decay channel to determine the Cabibbo-Kobayashi-Maskawa (CKM) matrix element |Vub| and to obtain a R-ratio to investigate lepton-flavor-universality violations. Results for the CKM matrix element may also shed light on the discrepancies seen between analyses of inclusive or exclusive decays. We calculate the decay form factors using lattice QCD with domain-wall light quarks and a relativistic b-quark. We analyze data at three lattice spacings with unitary pion masses down to 268 MeV. Our numerical results are interpolated/extrapolated to physical quark masses and to the continuum to obtain the vector and scalar form factors f+(q2) and f0(q2) with full error budgets at q2 values spanning the range accessible in our simulations. We provide a possible explanation of tensions found between results for the form factor from different lattice collaborations. Model- and truncation-independent z-parametrization fits following a recently proposed Bayesian-inference approach extend our results to the entire allowed kinematic range. Our results can be combined with experimental measurements of Bs→Ds and Bs→K semileptonic decays to determine |Vub|=3.8(6)×10−3. The error is currently dominated by experiment. We compute differential branching fractions and two types of R ratios, the one commonly used as well as a variant better suited to test lepton-flavor universality.
UNSPECIFIED
PhysRevD.107.114512
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Accepted/In Press date: 25 May 2023
Published date: 16 June 2023
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Funding Information:
We thank our RBC/UKQCD collaborators for helpful discussions and suggestions, Paolo Gambino for discussion on unitarity-constrained fits, and Greg Ciezarek for discussions of the LHCb form-factor data. We thank Edwin Lizarazo for contributions at early stages of this work. Computations used resources provided by the USQCD Collaboration, funded by the Office of Science of the U.S. Department of Energy and by the ARCHER UK National Supercomputing Service, as well as computers at Columbia University, Brookhaven National Laboratory, and the OMNI cluster of the University of Siegen. This document was prepared using the resources of the USQCD Collaboration at the Fermi National Accelerator Laboratory (Fermilab), a U.S. Department of Energy (DOE), Office of Science, HEP User Facility. Fermilab is managed by Fermi Research Alliance, LLC (FRA), acting under Contract No. DE-AC02-07CH11359. This work used the DiRAC Extreme Scaling service at the University of Edinburgh, operated by the Edinburgh Parallel Computing Centre on behalf of the STFC DiRAC HPC Facility. This equipment was funded by BEIS capital funding via STFC capital Grant No. ST/R00238X/1 and STFC DiRAC Operations Grant No. ST/R001006/1. DiRAC is part of the National e-Infrastructure. We used gauge-field configurations generated on the DiRAC Blue Gene Q system at the University of Edinburgh, part of the DiRAC Facility, funded by BIS National E-infrastructure Grant No. ST/K000411/1 and STFC Grants No. ST/H008845/1, No. ST/K005804/1, and No. ST/K005790/1. We thank BNL, Fermilab, the Columbia University, the University of Edinburgh, the University of Siegen, the STFC, and the U.S. DOE for providing the facilities essential for the completion of this work. This project has received funding from Marie Skłodowska-Curie Grants No. 659322 and 894103 (EU Horizon 2020) and U.K. STFC Grant No. ST/P000630/1 and is supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) through Grant No. 396021762—TRR 257 “Particle Physics Phenomenology after the Higgs Discovery.” The work of A. S. was supported in part by the U.S. DOE Contract No. DE-SC0012704.
Publisher Copyright:
© 2023 authors. Published by the American Physical Society.
Keywords:
hep-lat, hep-ph
Identifiers
Local EPrints ID: 477667
URI: http://eprints.soton.ac.uk/id/eprint/477667
ISSN: 2470-0010
PURE UUID: 33271d06-bc71-4e87-ae48-ca620411b08b
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Date deposited: 12 Jun 2023 16:50
Last modified: 30 Nov 2024 02:41
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Contributors
Author:
Ryan C. Hill
Author:
Amarjit Soni
Author:
J. Tobias Tsang
Author:
Oliver Witzel
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