Neutral B-meson mixing from three-flavor lattice QCD: Determination of the SU(3)-breaking ratio \xi

TL;DR

This paper calculates the SU(3)-breaking ratio  in neutral B-meson mixing using unquenched lattice QCD with three flavors, providing precise matrix elements and ratios relevant for understanding B-meson oscillations.

Contribution

The study introduces a detailed lattice QCD calculation of  and related parameters using improved actions, advancing the precision of B-meson mixing matrix elements.

Findings

 = 1.268 b1 0.063

Ratios of bag parameters B_{B_s}/B_{B_d} and CKM elements |V_{td}|/|V_{ts}| are provided

Methodology sets the stage for future studies of B mixing parameters in the Standard Model

Abstract

We study SU(3)-breaking effects in the neutral B_d-\bar B_d and B_s-\bar B_s systems with unquenched N_f=2+1 lattice 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 \xi=f_{B_s}\sqrt{B_{B_s}}/f_{B_d}\sqrt{B_{B_d}}=1.268+-0.063. We also present results for the ratio of bag parameters B_{B_s}/B_{B_d} and the ratio of CKM matrix elements |V_{td}|/|V_{ts}|. Although we focus on the calculation of \xi, the strategy and techniques described here will be employed in future extended studies of the B mixing parameters \Delta M_{d,s} and \Delta\Gamma_{d,s} in the Standard Model and beyond.