Impact of tag-side interference on time-dependent CP asymmetry measurements using coherent B⁰B⁰ pairs

Interference between Cabibbo-Kobayashi-Maskawa (CKM) favored b⃗cūd and doubly-CKM-suppressed b̅ →ūcd̅ amplitudes in final states used for B-flavor tagging gives deviations from the standard time evolution assumed in CP-violation measurements at B factories producing coherent B⁰B⁰ pairs. We evaluate these deviations for the standard time-dependent CP-violation measurements, the uncertainties they introduce in the measured quantities, and give suggestions for minimizing them. The uncertainty in the measured CP asymmetry for CP eigenstates is ≈2% or less. The time-dependent analysis of D^*π, proposed for measuring sin(2β+γ), must incorporate possible tag-side interference, which could produce asymmetries as large as the expected signal asymmetry.