First decay-time-dependent analysis of $B^{0} \to K_{S}^{0} \pi^{0}$ at Belle II

TL;DR

This paper presents the first decay-time-dependent analysis of the $B^{0} o K_{S}^{0} o ext{pi}^0$ decay at Belle II, measuring its branching fraction and CP asymmetry with a large data sample.

Contribution

It introduces the first decay-time-dependent measurement of $B^{0} o K_{S}^{0} ext{pi}^0$ decays at Belle II, providing new insights into CP violation in this channel.

Findings

Branching fraction measured as (11.0 ± 1.2 (stat) ± 1.0 (syst)) × 10^{-6}

CP asymmetry measured as -0.41_{-0.32}^{+0.30} (stat) ± 0.09 (syst)

Reconstructed about 135 signal candidates

Abstract

We report measurements of the branching fraction ($\mathcal{B}$) and direct $CP$-violating asymmetry ($A_{CP}$) of the charmless decay $B^{0} \to K^0 \pi^0$ at Belle II. A sample of $e^{+} e^{-}$ collisions, corresponding to $189.8 fb^{-1}$ of integrated luminosity, recorded at the $\Upsilon(4S)$ resonance is used for the first decay-time-dependent analysis of these decays within the experiment. We reconstruct about 135 signal candidates, and measure $\mathcal{B}(B^{0} \to K^{0} \pi^{0})= [11.0 \pm 1.2 (stat) \pm 1.0 (syst)] \times 10^{-6}$ and $A_{CP} (B^{0} \to K^{0} \pi^{0})= -0.41_{-0.32}^{+0.30} (stat) \pm 0.09 (syst)$.