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Probing the CKM Angle $γ$ with $B\toπK$ Decays

The decays $B^\pm\to π^\pm K$ and $B_d\to π^\mp K^\pm$ were observed by the CLEO collaboration last year; they may play an important role to probe the angle $γ$ of the unitarity triangle of the CKM matrix. After a general parametrization of their decay amplitudes within the Standard Model, strategies to constrain and determine the CKM angle $γ$ with the help of the corresponding CP-conserving and CP-violating observables are briefly 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 $γ$ by using additional experimental information on $B^\pm\to K^\pm K$ decays, and steps towards the control of electroweak penguins are pointed out.