B Mixing¹

The neutral B mesons, B⁰ and Bs⁰, can oscillate between their particle and antiparticle states owing to flavor-changing weak interactions. In recent years, techniques to detect these oscillations as a function of the meson's decay time have been developed. This article reviews the physics of flavor oscillations and summarizes theoretical predictions. The many observations that demonstrate the time dependence of oscillations are presented along with a combined measurement of its frequency, Δ md = 0.484 ± 0.015 ps⁻¹. The attempts to measure the Bs⁰ oscillation frequency, both directly and indirectly, are then summarized, currently resulting in a limit of Δ ms > 14.6 ps⁻¹ (95% CL). Finally, values for the CKM elements |Vtd| = (3.6 ± 0.4) × 10⁻³ and |Vts/Vtd| > 4.7 (95% CL) are extracted.