Framework for Identification of Neutral B Mesons

We introduce a method for the study of CP-violating asymmetries in tagged states of neutral $B$ mesons with arbitrary coherence properties. A set of time-dependent measurements is identified which completely specifies the density matrix of the initial state in a two-component space with basis vectors $B^0$ and ${\bar{B}}^0$, and permits a determination of phases in the Cabibbo-Kobayashi-Maskawa matrix. For a given tagging configuration, the measurement of decays both to flavor eigenstates and to CP eigenstates provides the necessary information.