Lepton CP asymmetries in B decays

In the decay of Y(4S), the decay time distribution of Y (4S) → f + X, where f is a final state that B⁰ or B can decay to, is the sum of the decay time distributions of B⁰ → f and B̄⁰ → f. Using this general rule, we estimate the sensitivity of single lepton CP violation measurements with respect to that of traditional di-lepton measurements. We find that the sensitivity of the single lepton method is comparable to or better than that of the di-lepton method. The two data samples are largely statistically independent, so that they can be combined to improve sensitivity. The advantage of the single lepton measurement increases for large mixings, which suggests that the single lepton method holds promise for B_s. We also discuss lepton asymmetry measurements on the Z⁰ peak and in hadron colliders. The achievable sensitivity with the currently available data is already in the range relevant to standard model predictions.