Measurement of the CKM angle $ϕ_3$ at Belle II

The precise measurement of the CKM angle $ϕ_3$ is important to further test the Standard Model description of $CP$ violation. The small values of the branching fractions of the decays involved in the measurement limits the precision, hence a larger dataset has to be accumulated to improve the precision. The Belle~II experiment at the SuperKEKB asymmetric-energy $e^+e^-$ collider aims to collect 50~ab$^{-1}$ of data, a factor of 50 more than that of its predecessor Belle. The accelerator has been successfully commissioned in 2016 and the first physics collisions were recorded in April 2018. The best sensitivity to $ϕ_3$ can be achieved by harnessing all possible final states of $B \to D^{(*)}K^{(*)}$ decays. With the full dataset, Belle~II is expected to achieve a precision of 1$^{\circ}$ for the angle $ϕ_3$. The expected sensitivities and rediscoveries from 2018 data are presented here.

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