First observation of $B_s^0\to J/\psi\eta$ and $B_s^0\to J/\psi\eta'$

TL;DR

This paper reports the first observation of the decay modes $B_s^0 o J/\,\eta$ and $B_s^0 o J/\eta'$, measuring their branching fractions and the ratio between them using data from the Belle detector at KEKB.

Contribution

First experimental measurement of $B_s^0\to J/\psi\eta$ and $B_s^0\to J/\psi\eta'$ decay modes with branching fractions and their ratio.

Findings

Branching fraction for $B_s^0\to J/\psi\eta$ is approximately 5.10 x 10^{-4}.

Branching fraction for $B_s^0\to J/\psi\eta'$ is approximately 3.71 x 10^{-4}.

The ratio of the two branching fractions is about 0.73.

Abstract

We report first observations of $B_s^0\to J/\psi\eta$ and $B_s^0\to J/\psi\eta'$. The results are obtained from 121.4 fb^{-1} of data collected at the $\Upsilon(5S)$ resonance with the Belle detector at the KEKB $e^+e^-$ collider. We obtain the branching fractions Br(B_s^0\to J/\psi\eta)= [5.10\pm 0.50(stat.)\pm 0.25(syst.)^{+1.14}_{-0.79}(N_{B_s^(*)\bar B_s^(*))] \times 10^{-4}, and Br(B_s^0\to J/\psi\eta')=[3.71\pm 0.61(stat.)\pm 0.18(syst.)^{+0.83}_{-0.57}(N_{B_s^(*)\bar B_s^(*))] \times 10^{-4}. The ratio of the two branching fractions is measured to be $\frac{Br(B_s\to J/\psi\eta')}{Br(B_s\to J/\psi \eta)} = 0.73\pm 0.14(stat.)\pm 0.02(syst.)$.