B(s)0-mixing matrix elements from lattice QCD for the Standard Model and beyond

Bazavov, A. et al. (2016) B(s)0-mixing matrix elements from lattice QCD for the Standard Model and beyond. Physical Review D, 93(11), 113016. (doi:10.1103/PhysRevD.93.113016)

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Abstract

We calculate—for the first time in three-flavor lattice QCD—the hadronic matrix elements of all five local operators that contribute to neutral B0- and Bs-meson mixing in and beyond the Standard Model. We present a complete error budget for each matrix element and also provide the full set of correlations among the matrix elements. We also present the corresponding bag parameters and their correlations, as well as specific combinations of the mixing matrix elements that enter the expression for the neutral B-meson width difference. We obtain the most precise determination to date of the SU(3)-breaking ratio ξ=1.206(18)(6), where the second error stems from the omission of charm-sea quarks, while the first encompasses all other uncertainties. The threefold reduction in total uncertainty, relative to the 2013 Flavor Lattice Averaging Group results, tightens the constraint from B mixing on the Cabibbo-Kobayashi-Maskawa (CKM) unitarity triangle. Our calculation employs gauge-field ensembles generated by the MILC Collaboration with four lattice spacings and pion masses close to the physical value. We use the asqtad-improved staggered action for the light-valence quarks and the Fermilab method for the bottom quark. We use heavy-light meson chiral perturbation theory modified to include lattice-spacing effects to extrapolate the five matrix elements to the physical point. We combine our results with experimental measurements of the neutral B-meson oscillation frequencies to determine the CKM matrix elements |Vtd|=8.00(34)(8)×10−3, |Vts|=39.0(1.2)(0.4)×10−3, and |Vtd/Vts|=0.2052(31)(10), which differ from CKM-unitarity expectations by about 2σ. These results and others from flavor-changing-neutral currents point towards an emerging tension between weak processes that are mediated at the loop and tree levels.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:DeTar, Professor Carleton and Bouchard, Dr Christopher
Authors: Bazavov, A., Bernard, C., Bouchard, C.M., Chang, C.C., DeTar, C., Du, D., El-Khadra, A.X., Freeland, E.D., Gámiz, E., Gottlieb, S., Heller, U.M., Kronfeld, A.S., Laiho, J., Mackenzie, P.B., Neil, E.T., Simone, J., 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
Copyright Holders:Copyright © 2016 American Physical Society
First Published:First published in Physical Review D 93(11): 113016
Publisher Policy:Reproduced in accordance with the publisher copyright policy

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