Kaon semileptonic vector form factor and determination of |Vus| using staggered fermions

A. Bazavov, C. Bernard, C. M. Bouchard, C. DeTar, Daping Du, A. X. El-Khadra, J. Foley, E. D. Freeland, E. Gámiz, Steven Gottlieb, U. M. Heller, Jongjeong Kim, A. S. Kronfeld, J. Laiho, L. Levkova, P. B. Mackenzie, E. T. Neil, M. B. Oktay, Si-Wei Qiu, J. N. Simone, R. Sugar, D. Toussaint, R. S. Van de Water, and Ran Zhou (Fermilab Lattice and MILC Collaborations)
Phys. Rev. D 87, 073012 – Published 23 April 2013

Abstract

Using staggered fermions and partially twisted boundary conditions, we calculate the K meson semileptonic decay vector form factor at zero momentum transfer. The highly improved staggered quark formulation is used for the valence quarks, while the sea quarks are simulated with the asqtad action (MILC Collaboration Nf=2+1 configurations). For the chiral and continuum extrapolation, we use two-loop continuum χPT, supplemented by partially quenched staggered χPT at one loop. Our result is f+Kπ(0)=0.9667±0.0023±0.0033, where the first error is statistical and the second is the sum in quadrature of the systematic uncertainties. This result is the first Nf=2+1 calculation with two lattice spacings and a controlled continuum extrapolation. It is also the most precise result to date for the vector form factor, and, although the central value is larger than previous unquenched lattice calculations, it is compatible with them within errors. Combining our value for f+Kπ(0) with the latest experimental measurements of K semileptonic decays, we obtain |Vus|=0.2238±0.0009±0.0005, where the first error is from f+Kπ(0) and the second one is experimental. As a byproduct of our calculation, we obtain the combination of low-energy constants (C12r+C34r(L5r)2)(Mρ)=(3.62±1.00)×106.

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  • Received 21 December 2012

DOI:https://doi.org/10.1103/PhysRevD.87.073012

© 2013 American Physical Society

Authors & Affiliations

A. Bazavov1, C. Bernard2, C. M. Bouchard3, C. DeTar4, Daping Du5, A. X. El-Khadra5, J. Foley4, E. D. Freeland6, E. Gámiz7,*, Steven Gottlieb8, U. M. Heller9, Jongjeong Kim10, A. S. Kronfeld11, J. Laiho12, L. Levkova4, P. B. Mackenzie11, E. T. Neil11, M. B. Oktay4, Si-Wei Qiu4, J. N. Simone11, R. Sugar13, D. Toussaint10, R. S. Van de Water11, and Ran Zhou8 (Fermilab Lattice and MILC Collaborations)

  • 1Physics Department, Brookhaven National Laboratory, Upton, New York, USA
  • 2Department of Physics, Washington University, St. Louis, Missouri, USA
  • 3Department of Physics, The Ohio State University, Columbus, Ohio, USA
  • 4Physics Department, University of Utah, Salt Lake City, Utah, USA
  • 5Physics Department, University of Illinois, Urbana, Illinois, USA
  • 6Department of Physics, Benedictine University, Lisle, Illinois, USA
  • 7CAFPE and Departamento de Física Teórica y del Cosmos, Universidad de Granada, Granada, Spain
  • 8Department of Physics, Indiana University, Bloomington, Indiana, USA
  • 9American Physical Society, Ridge, New York, USA
  • 10Department of Physics, University of Arizona, Tucson, Arizona, USA
  • 11Fermi National Accelerator Laboratory, Batavia, Illinois, USA
  • 12SUPA, School of Physics and Astronomy, University of Glasgow, Glasgow, United Kingdom
  • 13Department of Physics, University of California, Santa Barbara, California, USA

  • *megamiz@ugr.es

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Vol. 87, Iss. 7 — 1 April 2013

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