Weak Phase $\gamma$ From Ratio of $B\to K\pi$ Rates

The ratio of partial decay rates for charged and neutral $B$ mesons to $K \pi$finalstatesprovidesinformationontheweakphase$\gamma \equiv {\rm Arg} (V_{ub}^*)$ when augmented with information on the CP-violating asymmetry in the $K^{\pm }{\pi }^{\mp }$ mode. The requirements for a useful determination of $\gamma$ are examined in the light of present information about the decays $B^0 \to K^+ \pi^-$,$B^+ \to K^0 \pi^+$, and the corresponding charge-conjugate modes. The effects of electroweak penguins and rescattering corrections are noted, and proposals are made for estimating and measuring their importance.