Towards the Extraction of the CKM Angle $\gamma$

The determination of the angle $\gamma$ of the unitarity triangle of the CKM matrix is regarded as a challenge for future $B$-physics experiments. In this context, the decays $B^\pm\to \pi^\pm K$ and $B_d\to\pi^\mp K^\pm$, which were observed by the CLEO collaboration last year, received a lot of interest in the literature. After a general parametrization of their decay amplitudes, strategies to constrain and determine the CKM angle $\gamma$ with the help of the corresponding observables are reviewed. The theoretical accuracy of these methods is limited by certain rescattering and electroweak penguin effects. It is emphasized that the rescattering processes can be included in the bounds on $\gamma$ by using additional experimental information on $B^\pm\to K^\pm K$ decays, and steps towards the control of electroweak penguins are pointed out. Moreover, strategies to probe the CKM angle $\gamma$ with the help of $B_s\to K\bar{K}$ decays are briefly discussed.