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

Bazavov, A. et al. (2013) Kaon semileptonic vector form factor and determination of |V_us| using staggered fermions. Physical Review D, 87(7), 073012. (doi: 10.1103/PhysRevD.87.073012)

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 fKπ+(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 fKπ+(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 fKπ+(0) and the second one is experimental. As a byproduct of our calculation, we obtain the combination of low-energy constants (Cr12+Cr34−(Lr5)2)(Mρ)=(3.62±1.00)×10−6.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Laiho, Dr John and Bouchard, Dr Chris
• Authors: Bazavov, A., Bernard, C., Bouchard, C.M., DeTar, C., Du, D., El-Khadra, A. X., Foley, J., Freeland, E. D., Gámiz, E., Gottlieb, S., Heller, U. M., Kim, J., Kronfeld, A. S., Laiho, J., Levkova, L., Mackenzie, P. B., Neil, E. T., Oktay, M. B., Qiu, S.-W., Simone, J. N., Sugar, R., Toussaint, D., Van de Water, R. S., and Zhou, R.
• 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): 1550-2368

Project Code	Award No	Project Name	Principal Investigator	Funder's Name	Funder Ref	Lead Dept
48195	1	Investigations in Quantum Chromodynamics and Physics Beyond the Standard Model	Christine Davies	Science & Technologies Facilities Council (STFC)	ST/G00059X/1	P&A - PHYSICS & ASTRONOMY
57372	1	Phenomenology from Lattice QCD and Collider Physics	Christine Davies	Science & Technologies Facilities Council (STFC)	ST/J000442/1	P&A - PHYSICS & ASTRONOMY