Measurement of the $B^+/B^0$ production ratio in $e^+e^-$ collisions at the $\Upsilon(4S)$ resonance using $B \rightarrow J/\psi(\ell\ell) K$ decays at Belle

TL;DR

This paper reports a precise measurement of the ratio of charged to neutral B meson production in $mbda(4S)$ decays, using $J/aphi(llll)$ decays at Belle with 711 fb$^{-1}$ of data.

Contribution

It provides the most precise measurement to date of the $B^+/B^0$ production ratio at the $mbda(4S)$ resonance, improving understanding of B meson production asymmetries.

Findings

Measured the ratio as 1.065 with combined uncertainties.

Achieved the most precise measurement of this ratio to date.

Quantified uncertainties including statistical, systematic, and isospin assumptions.

Abstract

We measure the ratio of branching fractions for the $\Upsilon (4S)$ decays to $B^+B^-$ and $B^0\bar{B}{}^0$ using $B^+ \rightarrow J/\psi(\ell\ell) K^+$ and $B^0 \rightarrow J/\psi(\ell\ell) K^0$ samples, where $J/\psi(\ell\ell)$ stands for $J/\psi \to \ell^+\ell^-$ ($\ell = e$ or $\mu$), with $711$ fb$^{-1}$ of data collected at the $\Upsilon(4S)$ resonance with the Belle detector. We find the decay rate ratio of $\Upsilon(4S) \rightarrow B^+B^-$ over $\Upsilon(4S) \rightarrow B^0\bar{B}{}^0$ to be $1.065\pm0.012\pm 0.019 \pm 0.047$, which is the most precise measurement to date. The first and second uncertainties are statistical and systematic, respectively, and the third uncertainty is systematic due to the assumption of isospin symmetry in $B \to J/\psi(\ell\ell) K$.