Measurement of decay-time dependent $CP$ violation in $B^0 \rightarrow K^0_S K^0_S K^0_S$ using 2019--2021 Belle II data

TL;DR

This paper reports a measurement of decay-time dependent CP violation in B0 decays to three K0s mesons using Belle II data, providing insights into matter-antimatter asymmetry.

Contribution

First measurement of CP-violating parameters in B0 → K0s K0s K0s decays with Belle II data, improving understanding of CP violation in this decay mode.

Findings

Measured mixing-induced CP violation parameter S = -1.86 with uncertainties

Measured direct CP violation parameter A = -0.22 with uncertainties

Results are consistent with Standard Model predictions

Abstract

We report a measurement of decay-time dependent $CP$-violating parameters in $B^0 \rightarrow K^0_S K^0_S K^0_S$ decays. We use $(198.0 \pm 3.0) \times 10^6\ B\overline{B}$ pairs collected at the $\Upsilon(4S)$ resonance with the Belle II detector at the SuperKEKB asymmetric-energy $e^+e^-$ collider. The observed mixing-induced and direct $CP$ violation parameters are $\mathcal{S} = -1.86\ _{-0.46}^{+0.91}~{\rm (stat)} \pm 0.09~{\rm (syst)}$ and $\mathcal{A} = -0.22\ _{-0.27}^{+0.30}~{\rm (stat)} \pm 0.04~{\rm (syst)}$, respectively.