Precision measurements of the CKM parameters (mainly $\gamma/\phi_{3}$ measurements)

Abstract

The CKM angle $\gamma/\phi_{3}$ is the only one that is accessible with tree level decays in a theoretically clean way such that it provides a precision test of $CP$ violation in the standard model. The Belle II experiment is a substantial upgrade of the Belle detector and will operate at the SuperKEKB asymmetric-energy $e^{+}e^{-}$ collider. The accelerator has already successfully completed the first phase of commissioning in 2016 and first $e^{+}e^{-}$ collisions in Belle II happened during April 2018. The design luminosity of SuperKEKB is 8 $\times$ 10$^{35}$ cm$^{-2}$s$^{-1}$ and the Belle II experiment aims to record 50 ab$^{-1}$ of data, a factor of 50 more than its predecessor (Belle). The key method to measure $\phi_{3}$ is through interference between the $B^- \to D^0 K^-$ and $B^- \to \bar{D^{0}} K^{-}$ decays which occurs if the final state of the charm-meson decay is accessible to both the $D^0$ and $\bar{D^{0}}$ mesons. To achieve the best sensitivity, a large variety of $D$ and $B$ decay modes are required, which is possible at the Belle II experiment as almost any final state can be reconstructed including those with photons. With the ultimate Belle II data sample of 50 ab$^{-1}$, a determination of $\phi_{3}$ with a precision of $1^{\circ}$ or better is foreseen. We explain herein the details of the planned measurements at Belle II.