Discrete ambiguities in extracting weak phases fromBdecays

Phases of elements of the Cabibbo-Kobayashi-Maskawa (CKM) matrix, as obtained using decays of $B$ mesons to ${\pi }^{+}{\pi }^{-}$, ${\pi }^{\pm }{K}^{\mp }$, and ${\pi }^{+}{K}^0$ or ${\pi }^{-}{\overline{K}}^0$, are shown to have a class of discrete ambiguities. In most cases these can be eliminated using other information on CKM phases.