Measurement of decay-time-dependent $\text{CP}$ violation in $B^0\to J/\psi K_S^0$ decays using 2019-2021 Belle II data

Abstract

We report a measurement of the mixing-induced and direct $\text{CP}$ violation parameters $S_{\text{CP}}$ and $A_{\text{CP}}$ from $B^0\to J/\psi K_S^0$ decays reconstructed by the Belle II experiment at the SuperKEKB asymmetric-energy electron-positron collider. The data, collected at the center-of-mass energy of the ${\rm Y}(4S)$ resonance, correspond to $190{\text{fb}}^{-1}$ of integrated luminosity. We measure $S_{\text{CP}}=0.720\pm 0.062\pm 0.016$ and $A_{\text{CP}}=0.094\pm 0.044_{-0.017}^{+0.042}$, where the first uncertainties are statistical and the second systematic. In the Standard Model, $S_{\text{CP}}$ equals $\sin (2{\varphi }_1)$ to a good approximation.

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Cited by in corpus (8)

• New graph-neural-network flavor tagger for Belle II and measurement of $\sin 2{\varphi }_1$ in $B^0\to J/\psi K_{\text{S}}^0$ decays
• Measurement of branching fractions and direct $CP$ asymmetries for $B\to K\pi$ and $B\to \pi \pi$ decays at Belle II
• Measurement of $CP$ asymmetries in $B^0\to \varphi K_S^0$ decays with Belle II
• Measurement of $CP$ asymmetries in $B^0\to K_S^0{\pi }^0\gamma$ decays at Belle II
• Precision measurement of the $B^0$ meson lifetime using $B^0\to J/\psi K^{\ast 0}$ decays with the ATLAS detector
• Measurement of $CP$ asymmetries in $B^0\to {\eta }^{\prime }{K}_s^0$ decays at Belle II
• Measurement of the branching fraction, polarization, and time-dependent $CP$ asymmetry in $B^0\to {\rho }^{+}{\rho }^{-}$ decays and constraint on the CKM angle ${\varphi }_2$
• Lepton flavor violating top quark FCNC processes at the $\mu$TRISTAN