D→K, lν semileptonic decay scalar form factor and |Vcs| from lattice QCD

Na, H., Davies, C. , Follana, E., Lepage, G. and Shigemitsu, J. (2010) D→K, lν semileptonic decay scalar form factor and |Vcs| from lattice QCD. Physical Review D, 82(11), (doi: 10.1103/PhysRevD.82.114506)

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Publisher's URL: http://dx.doi.org/10.1103/PhysRevD.82.114506

Abstract

We present a new study of D semileptonic decays on the lattice which employs the highly improved staggered quark action for both the charm and the light valence quarks. We work with MILC unquenched N<sub>f</sub>=2+1 lattices and determine the scalar form factor f<sub>0</sub>(q<sup>2</sup>) for D→K, lν semileptonic decays. The form factor is obtained from a scalar current matrix element that does not require any operator matching. We develop a new approach to carrying out chiral/continuum extrapolations of f<sub>0</sub>(q<sup>2</sup>). The method uses the kinematic “z”variable instead of q<sup>2</sup> or the kaon energy E<sub>K</sub> and is applicable over the entire physical q<sup>2</sup> range. We find f<sub>0</sub><sup>D→K</sup>(0)≡f<sub>+</sub><sup>D→K</sup>(0)=0.747(19) in the chiral plus continuum limit and hereby improve the theory error on this quantity by a factor of ∼4 compared to previous lattice determinations. Combining the new theory result with recent experimental measurements of the product f<sub>+</sub> <sup>D→K</sup>(0)*|V<sub>cs</sub>| from BABAR and CLEO-c leads to a very precise direct determination of the CKM matrix element |V<sub>cs</sub>|, |V<sub>cs</sub>|=0.961(11)(24), where the first error comes from experiment and the second is the lattice QCD theory error. We calculate the ratio f<sub>+</sub> <sup>D→K</sup>(0)/f<sub>D</sub> <sub>s</sub> and find 2.986±0.087  GeV-1 and show that this agrees with experiment.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Follana, Dr Eduardo and Shigemitsu, Prof Junko and Davies, Professor Christine
Authors: Na, H., Davies, C., Follana, E., Lepage, G., and Shigemitsu, J.
College/School:College of Science and Engineering > School of Physics and Astronomy
Journal Name:Physical Review D
Publisher:American Physical Society
ISSN:1550-7998
ISSN (Online):1089-4918

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
481951Investigations in Quantum Chromodynamics and Physics Beyond the Standard ModelChristine DaviesScience & Technologies Facilities Council (STFC)ST/G00059X/1Physics and Astronomy