Observation of the decay $B_s^0\rightarrow K^0\overline{K}^0$

TL;DR

This paper reports the first observation of the decay $B_s^0\rightarrow K^0\overline{K}^0$ using data from the Belle detector, measuring its branching fraction with high statistical significance.

Contribution

The paper presents the first measurement and observation of the decay $B_s^0\rightarrow K^0\overline{K}^0$ at the $S$ resonance.

Findings

Branching fraction measured as approximately 19.6 x 10^{-6}

Decay observed with a significance of 5.1 standard deviations

First experimental observation of this decay mode

Abstract

We measure the decay $B_s^0\rightarrow K^0\overline{K}^0$ using data collected at the $\Upsilon(5S)$ resonance with the Belle detector at the KEKB $e^+e^-$ collider. The data sample used corresponds to an integrated luminosity of 121.4 ${\rm fb^{-1}}$. We measure a branching fraction $\mathcal{B}(B_s^0\rightarrow K^0\overline{K}^0) = [19.6\,^{+5.8}_{-5.1}({\rm stat.})\,\pm1.0({\rm sys.})\,\pm 2.0(N^{}_{B_s^0\overline{B}_s^0})]\times 10^{-6}$ with a significance of 5.1 standard deviations. This measurement constitutes the first observation of this decay.