Measurement of $CP$ asymmetries in $B^0\to K_S^0{\pi }^0\gamma$ decays at Belle II

Abstract

We report measurements of time-dependent $CP$ asymmetries in $B^0\to K_S^0{\pi }^0\gamma$ decays based on a data sample of $(388\pm 6)\times 10^6$ $B\bar{B}$ events collected at the ${\rm Y}(4S)$ resonance with the Belle II detector. The Belle II experiment operates at the SuperKEKB asymmetric-energy $e^{+}{e}^{-}$ collider. We measure decay-time distributions to determine $CP$-violating parameters $S$ and $C$. We determine these parameters for two ranges of $K_S^0{\pi }^0$ invariant mass: $m(K_S^0{\pi }^0)\in (0.8,1.0)$ $GeV/c^2$, which is dominated by $B^0\to K^{\ast 0}(\to K_S^0{\pi }^0)\gamma$ decays, and a complementary region $m(K_S^0{\pi }^0)\in (0.6,0.8)\cup (1.0,1.8)$ $GeV/c^2$. Our results have improved precision as compared to previous measurements and are consistent with theory predictions.

8 pages, 2 figures

References in corpus (14)

• An Introduction to PYTHIA 8.2
• B->V gamma Beyond QCD Factorisation
• Track Finding at Belle II
• Measurement of the ratio of branching fractions BR(B0 -> K*0 gamma)/BR(Bs0 -> phi gamma) and the direct CP asymmetry in B0 -> K*0 gamma
• Time-Dependent CP Asymmetries in B0 -> Ks pi0 gamma transitions
• The birds and the Bs in RS: the b to s gamma penguin in a warped extra dimension
• The Design, Construction, Operation and Performance of the Belle II Silicon Vertex Detector
• Evidence for Isospin Violation and Measurement of $CP$ Asymmetries in $B\to K^{\ast }(892)\gamma$
• Strong constraints on the $b\to s\gamma$ photon polarisation from $B^0\to K^{\ast 0}{e}^{+}{e}^{-}$ decays
• Measurement of the photon polarization in ${\Lambda }_b\to \Lambda \gamma$ decays
• Measurement of decay-time-dependent $\text{CP}$ violation in $B^0\to J/\psi K_S^0$ decays using 2019-2021 Belle II data
• Measurement of the $B^0$ lifetime and flavor-oscillation frequency using hadronic decays reconstructed in 2019-2021 Belle II data
• SUSY contributions to CP violations in $b\to s$ and $b\to d$ transitions facing on new data
• Imprint of SUSY in radiative B-meson decays