Measurement of the Angle $\phi_1(\beta)$ and $B \bar B$ Mixing (Recent Results from BaBar and Belle)

TL;DR

Recent measurements from BaBar and Belle on B meson mixing and CP violation provide precise results consistent with the Standard Model, while also hinting at potential new physics in penguin decay modes.

Contribution

This paper presents the latest experimental results on B meson mixing and CP violation, including measurements of $eta$ and $ au_{B}$, and explores possible deviations indicating new physics.

Findings

Measurement of $ au_{B}$ with 1.2% accuracy.

Combined $ ext{sin} 2eta$ results agree with global CKM fit.

Penguin decay modes show a 2.5$\sigma$ deviation from Standard Model expectations.

Abstract

Recent results from BaBar and Belle experiments on $B \bar B$ mixing and $\sin 2\phi_1$ are presented. Accuracy of $\Delta m_d$ measurements has reached 1.2%. Higher order effects within the Standard Model or possible new physics effect that might appear in the $B \bar B$ mixing through non-zero $\Delta \Gamma/\Gamma$, CP violation, or $CPT$ violation have been explored. The BaBar and Belle results on $\sin 2\phi_1$ from the $b \to c \bar{c} s$ modes are in good agreement with each other and a combined result with an accuracy of 8% is in good agreement with a global CKM fit. A simple average of the $\sin 2\phi_1$ values that were measured in the penguin-loop dominated decay modes, $\phi K_S$, $\eta^{\prime} K_S$, and $K^+ K^- K_S$, shows about 2.5$\sigma$ deviation from the Standard Model.