PubDB | BELLE2-PUB-PH-2025-018

Abstract	We perform a measurement of time-dependent \CP violation parameters in $\Bd \to \KS \piz \g$ decays using a dataset of approximately $770 \times 10^6$ and $550 \times 10^6$ \BBbar pairs collected at the $\Y4S$ resonance by the Belle and Belle~II experiments, respectively. The measured parameters for the combined dataset in the $K^{0}(892)$ dominated region ($M_{\KS\piz} \in [0.8,1.0]\gevcc$) are $\SCP = 0.08 \pm 0.16 \pm 0.02$ and $\CCP = -0.09 \pm 0.08 \pm 0.04$. For the non-$K^{0}(892)$ region ($M_{\KS\piz} \in [1.0,1.8]\gevcc$), the corresponding values are $\SCP = -0.32 \pm 0.33 \pm 0.08$ and $\CCP = -0.07 \pm 0.17 \pm 0.08$. The first quoted uncertainties are statistical, while the second ones are systematic. These results are more precise than previous measurements and consistent with Standard Model predictions.
Tags	Belle Run 1 Run 2 (partial)
Working group	Time Dependent CP Violation
Principal authors	@ Rishabh Mehta, Gagan Mohanty, Rahul Tiwary
Reference	submitted to JHEP
Links	arXiv:2606.04496,

Abstract

We perform a measurement of time-dependent \CP violation parameters in $\Bd \to \KS \piz \g$ decays using a dataset of approximately $770 \times 10^6$ and $550 \times 10^6$ \BBbar pairs collected at the $\Y4S$ resonance by the Belle and Belle~II experiments, respectively. The measured parameters for the combined dataset in the $K^{*0}(892)$ dominated region ($M_{\KS\piz} \in [0.8,1.0]\gevcc$) are $\SCP = 0.08 \pm 0.16 \pm 0.02$ and $\CCP = -0.09 \pm 0.08 \pm 0.04$. For the non-$K^{*0}(892)$ region ($M_{\KS\piz} \in [1.0,1.8]\gevcc$), the corresponding values are $\SCP = -0.32 \pm 0.33 \pm 0.08$ and $\CCP = -0.07 \pm 0.17 \pm 0.08$. The first quoted uncertainties are statistical, while the second ones are systematic. These results are more precise than previous measurements and consistent with Standard Model predictions.

Measurement of $CP$ asymmetries in $B^0 \to K^0_S \pi^0 \gamma$ at Belle and Belle II