Sumitted to PubDB: 2023-11-06

Category: Proceeding, Visibility: Public

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Authors	Oskar Tittel
Date	2023-11-06
Belle II Number	BELLE2-CONF-PROC-2023-044
Abstract	We report on new time-dependent \CP violation measurements using the full dataset of \belletwo collected between 2019-2022 and on improved analysis software. Hadronic penguin decays, which proceed via a $b\to \text{qqbar}s$ transition, are loop dominated, and thus sensitive to new physics. in this class, we measure the time-dependent \CP violation parameters $\text{ccp}=-0.19\pm 0.08\pm 0.03$ and $\text{scp}=0.67\pm 0.10\pm 0.04$ in the decay $\text{Bz}\to {\eta }^{\prime }{K}_S^0$. In $b\to \gamma (s,d)$ transitions, radiative penguin decays, the mixing-induced \CP violation is suppressed by the polarization of the photon. New physics contributions could, however, lead to a sizable mixing-induced term. Here, we measure $\text{ccp}=0.10\pm 0.13\pm 0.03$ and $\text{scp}=0.00\pm 0.27\pm 0.04$ in exclusive decays to $\text{Bz}\to K^{\ast 0}\gamma$ and $\text{ccp}=-0.06\pm 0.25\pm 0.07$ and $\text{scp}=0.04\pm 0.45\pm 0.10$ in inclusive $\text{Bz}\to K_S^0{\pi }^0\gamma$ decays excluding a $K^{\ast 0}$ mass-region. These measurements require a flavor tagging algorithm. A flavor tagger based on a graph neural network was developed at \belletwo. The increased effective tagging efficiency of ${ϵ}_{tag}=(37.40\pm 0.43\pm 0.34)\mathrm{\%}$ is validated on the channel $\text{Bz}\to J/\psi K_S^0$. The measured values are $\text{ccp}=-0.035\pm 0.026\pm 0.012$ and $\text{scp}=0.724\pm 0.035\pm 0.014$

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