Observation of the decay $B^0 \to J/\psi \eta$

TL;DR

This paper reports the first observation of the decay mode $B^0 o J/ar{ u} u$ using a large data sample from the Belle detector, measuring its branching fraction with high significance.

Contribution

The study provides the first experimental evidence for the decay $B^0 o J/ u u$, expanding understanding of rare B meson decay processes.

Findings

Significance of 8.1 sigma for the decay observation

Branching fraction measured as (9.5 ± 1.7 (stat) ± 0.8 (syst))×10^{-6}

Data sample contains 449 million $Bar{B}$ pairs

Abstract

We report the first observation of $B^0 \to J/\psi \eta$ decay. These results are obtained from a data sample that contains 449 million $B\bar{B}$ pairs accumulated at the $\Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider. We observe a signal with a significance of 8.1$\sigma$ and obtain a branching fraction of (9.5 $\pm$ 1.7 (stat) $\pm$ 0.8 (syst))$\times 10^{-6}$.