Improved Vcs determination using precise lattice QCD form factors for D → Kℓν

Chakraborty, B., Parrott, W.G., Bouchard, C. , Davies, C.T.H. , Koponen, J. and Lepage, G.P. (2021) Improved Vcs determination using precise lattice QCD form factors for D → Kℓν. Physical Review D, 104(3), 034505. (doi: 10.1103/PhysRevD.104.034505)

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We provide a 0.8%-accurate determination of V c s from combining experimental results for the differential rate of D → K semileptonic decays with precise form factors that we determine from lattice QCD. This is the first time that V c s has been determined with an accuracy that allows its difference from 1 to be seen. Our lattice QCD calculation uses the Highly Improved Staggered Quark (HISQ) action for all valence quarks on gluon field configurations generated by the MILC collaboration that include the effect of u , d , s and c HISQ quarks in the sea. We use eight gluon field ensembles with five values of the lattice spacing ranging from 0.15 fm to 0.045 fm and include results with physical u / d quarks for the first time. Our calculated form factors cover the full q 2 range of the physical decay process and enable a Standard Model test of the shape of the differential decay rate as well as the determination of V c s from a correlated weighted average over q 2 bins. We obtain | V c s | = 0.9663 ( 53 ) latt ( 39 ) exp ( 19 ) η E W ( 40 ) EM , where the uncertainties come from lattice QCD, experiment, short-distance electroweak and electromagnetic corrections, respectively. This last uncertainty, neglected for D → K ℓ ν hitherto, now needs attention if the uncertainty on V c s is to be reduced further. We also determine V c s values in good agreement using the measured total branching fraction and the rates extrapolated to q 2 = 0 . Our form factors enable tests of lepton flavour universality violation. We find the ratio of branching fractions for D 0 → K − with μ and e in the final state to be R μ / e = 0.9779 ( 2 ) latt ( 50 ) E M in the Standard Model, with the uncertainty dominated by that from electromagnetic corrections.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Davies, Professor Christine and Parrott, Mr William and Bouchard, Dr Chris and Koponen, Dr Jonna
Authors: Chakraborty, B., Parrott, W.G., Bouchard, C., Davies, C.T.H., Koponen, J., and Lepage, G.P.
College/School:College of Science and Engineering > School of Physics and Astronomy
Journal Name:Physical Review D
Publisher:American Physical Society
ISSN (Online):2470-0029
Published Online:24 August 2021
Copyright Holders:Copyright © 2021 American Physical Society
First Published:First published in Physical Review D 104(3): 034505
Publisher Policy:Reproduced under a Creative Commons License

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
162894Precision results for particle physics from lattice QCD: Computing resources and software support for the UKQCD physics programme.Christine DaviesScience and Technology Facilities Council (STFC)ST/H00887X/1P&S - Physics & Astronomy