Measurement of Time-dependent $CP$ Asymmetries in $B^{0}\to K_S^0 \eta \gamma$ Decays

TL;DR

This paper measures time-dependent $CP$ violation parameters in $B^0 o K_S^0 \eta \gamma$ decays using a large data sample from the Belle experiment, providing insights into $CP$ violation in rare $B$ decays.

Contribution

First measurement of $CP$ violation parameters in $B^0 o K_S^0 \eta \\gamma$ decays with a large dataset from Belle, expanding understanding of $CP$ violation in radiative $B$ decays.

Findings

$CP$ violation parameter ${ m S} = -1.32 \\pm 0.77 \\pm 0.36$

$CP$ violation parameter ${ m A} = -0.48 \\pm 0.41 \\pm 0.07$

Results consistent with Standard Model expectations within uncertainties.

Abstract

We report a measurement of time-dependent $CP$ violation parameters in ${B^0 \to K_S^0 \eta \gamma}$ decays. The study is based on a data sample, containing ${772 \times 10^6 B\bar{B}}$ pairs, that was collected at the $\Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider. We obtain the $CP$ violation parameters of ${{\cal S} = -1.32 \pm 0.77 {\rm (stat.)} \pm 0.36{\rm (syst.)}}$ and ${{\cal A} = -0.48 \pm 0.41 {\rm (stat.)} \pm 0.07{\rm (syst.)}}$ for the invariant mass of the $K_S^0 \eta$ system up to 2.1 GeV/$c^2$.