We study SU(3)-breaking effects in the neutral B d-B ̄d and B s-B ̄s systems with unquenched N f=2+1 lattice quantum chromodynamics (QCD). We calculate the relevant matrix elements on the MILC collaboration's gauge configurations with asqtad-improved staggered sea quarks. For the valence light-quarks (u, d, and s) we use the asqtad action, while for b quarks we use the Fermilab action. We obtain ξ=f Bs√B Bsf Bd√B Bd=1.268±0.063. We also present results for the ratio of bag parameters B BsB Bd and the ratio of Cabibbo-Kobayashi- Maskawa matrix elements |V td|/|V ts|. Although we focus on the calculation of ξ, the strategy and techniques described here will be employed in future extended studies of the B mixing parameters ΔM d,s and ΔΓ d,s in the standard model and beyond.
ASJC Scopus subject areas
- Nuclear and High Energy Physics