Bs → D*s Form Factors for the full q² range from lattice QCD

Harrison, J. and Davies, C. T.H. (2022) Bs → D*s Form Factors for the full q² range from lattice QCD. Physical Review D, 105(9), 094506. (doi: 10.1103/PhysRevD.105.094506)

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Abstract

We compute the Standard Model semileptonic vector and axial-vector form factors for B s → D ∗ s decay across the full q 2 range using lattice QCD. We use the highly improved staggered quark (HISQ) action for all valence quarks, enabling us to normalize weak currents nonperturbatively. Working on second-generation MILC ensembles of gluon field configurations which include u , d , s , and c HISQ sea quarks and HISQ heavy quarks with masses from that of the c mass up to that of the b on the ensemble with the smallest lattice spacing, allows us to map out the heavy quark mass dependence of the form factors, and to constrain the associated discretization effects. We can then determine the physical form factors at the b mass. We use these to construct the differential and total rates for Γ ( B 0 s → D * − s ℓ + ν ℓ ) and find Γ ℓ = e / | η EW V c b | 2 = 2.07 ( 17 ) latt ( 2 ) EM × 10 13     s − 1 , Γ ℓ = μ / | η EW V c b | 2 = 2.06 ( 16 ) latt ( 2 ) EM × 10 13     s − 1 , and Γ ℓ = τ / | η EW V c b | 2 = 5.14 ( 37 ) latt ( 5 ) EM × 10 12     s − 1 , where η EW contains the short-distance electroweak correction to G F , the first uncertainty is from our lattice calculation, and the second allows for long-distance QED effects. The ratio R ( D * − s ) ≡ Γ ℓ = τ / Γ ℓ = μ = 0.2490 ( 60 ) latt ( 35 ) EM . We also obtain a value for the ratio of decay rates Γ ℓ = μ ( B s → D s ) / Γ ℓ = μ ( B s → D ∗ s ) = 0.443 ( 40 ) latt ( 4 ) EM , which agrees well with recent LHCb results. We can determine V c b by combining our lattice results across the full kinematic range of the decay with experimental results from LHCb and obtain | V c b | = 42.2 ( 1.5 ) latt ( 1.7 ) exp ( 0.4 ) EM × 10 − 3 . A comparison of our lattice results for the shape of the differential decay rate to the binned, normalized differential decay rate from LHCb shows good agreement. We also test the impact of new physics couplings on angular observables and ratios which are sensitive to lepton flavor universality violation.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Harrison, Dr Judd and Davies, Professor Christine
Authors: Harrison, J., and Davies, C. T.H.
College/School:College of Science and Engineering > School of Physics and Astronomy
Journal Name:Physical Review D
Publisher:American Physical Society
ISSN:2470-0010
ISSN (Online):2470-0029
Published Online:27 May 2022
Copyright Holders:Copyright © 2022 American Physical Society
First Published:First published in Physical Review D 105(9): 094506
Publisher Policy:Reproduced under a Creative Commons License

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
169715Phenomenology from Lattice QCD and collider physicsChristine DaviesScience and Technology Facilities Council (STFC)ST/L000466/1P&S - Physics & Astronomy
173809Phenomenology from Lattice QCD and Collider PhysicsChristine DaviesScience and Technology Facilities Council (STFC)ST/P000746/1P&S - Physics & Astronomy