Observation of the decay $B^0 \to J/\psi \omega$ at Belle II

TL;DR

This paper reports the first observation and precise measurement of the branching fraction for the decay $B^0 o J/ au \, ext{omega}$ using data from the Belle II detector, significantly advancing understanding of B meson decays.

Contribution

The study provides the first observation of the decay $B^0 o J/\psi \omega$ with a high significance and a more precise branching fraction measurement than previous experiments.

Findings

First observation of $B^0 \to J/\psi \omega$ decay.

Measured branching fraction: $(2.16 \pm 0.30 \pm 0.14) \times 10^{-5}$.

Significance of 6.5 standard deviations.

Abstract

We measure the branching fraction of the decay $B^0 \to J/\psi \omega$ using data collected with the Belle II detector at the SuperKEKB collider. The data contain $(387 \pm 6) \times 10^6$ $B\overline{B}$ meson pairs produced in energy-asymmetric $e^+e^-$ collisions at the $\Upsilon (4S)$ resonance. The measured branching fraction $\mathcal{B}(B^0 \to J/\psi \omega) = \left( 2.16 \pm 0.30 \pm 0.14 \right) \times 10^{-5}$, where the first uncertainty is statistical and the second is systematic, is more precise than previous results and constitutes the first observation of the decay with a significance of $6.5$ standard deviations.