Speaker
Description
[This talk is a combination of several submitted abstracts, including the following.]
In the Belle II experiment, we have accumulated integrated luminosity of more than 100 fb$^{-1}$ after starting the physics data taking in 2019. It is comparable to the data sets used for the $B^0$ lifetime $\tau_{B^0}$ and mixing $\Delta m_d$ measurements in the BABAR and Belle. To demonstrate high accuracy measurements using the decay time difference of the $B^0$-$\bar{B}^0$ system which is one of the most essential inputs of the time-dependent $CP$ violation study at the $B$-factory experiment, we measure $\tau_{B^0}$ and $\Delta m_d$ with resolution function refined for the high-statistics data. Since most of the $CP$-eigenstates are not flavor non-specific, we determine the flavor of $B^0$ meson using the remnants based on multivariable analysis after reconstructing the signal. It is validated using the control samples of hadronic decays $B \to D^{(*) }h ~(h = K ~{\rm or}~ \pi)$ and effective tagging efficiency is estimated. We present results of these studies related to the $CP$ violation measurements with high-statistics data samples. We also report about the reconstruction of the decays used for the $CP$ violation and a measurement of the time integrated mixing parameter, $\chi_d$.
