Towards more precise determinations of the CKM phase $\beta$

TL;DR

This paper introduces a new flavor symmetry relation for more precise determination of the CKM phase beta, reducing uncertainties from V_ub contributions and relying solely on SU(3) symmetry without additional assumptions.

Contribution

It presents a novel relation that suppresses V_ub effects in beta measurements, enhancing precision using only SU(3) flavor symmetry.

Findings

Current data fluctuates at 2σ from expectations.

Possible hints of unexpected V_ub contributions or isospin breaking.

Relation improves the accuracy of beta determination.

Abstract

We derive a new flavor symmetry relation for the determination of the weak phase $\beta=\phi_1$ from time-dependent CP asymmetries and $B \to J/\psi P$ decay rates. In this relation, the contributions to $\sin2\beta$ proportional to $V_{ub}$ are parametrically suppressed compared to the contributions in the $B \to J/\psi K^0$ time-dependent CP asymmetry alone. This relation uses only $SU(3)$ flavor symmetry, and does not require further diagrammatic assumptions. The current data either fluctuate at the $2\sigma$ level from expectations, or may hint at effects of unexpected magnitude from contributions proportional to $V_{ub}$ or from isospin breaking.