Rescattering and electroweak penguin effects in determinations of the weak phase γ

Determinations of the CKM phase γ from weak nonleptonic B decays are affected by electroweak (EW) penguins and rescattering effects. In this talk I explain how the EW penguin effects can be controlled with the help of SU(3) symmetry, by relating them to tree-level amplitudes. The impact of the final-state interactions on the determination of γ from B+→Kπ decays is studied numerically, showing that they can be important. A few alternative methods are discussed which use additional decays to eliminate their effects.