Simultaneous measurement of the B0 meson lifetime and mixing frequency with B0→D*-ℓ+v ℓ decays

We measure the B0 lifetime τB0 and the B 0-B̄0 oscillation frequency Δmd with a sample of approximately 14000 exclusively reconstructed B 0→D*-ℓ+vℓ signal events, selected from 23 million BB̄ pairs recorded at the Y(45) resonance with the BABAR detector at the Stanford Linear Accelerator Center. The decay position of the other B is determined with the remaining tracks in the event, and its b-quark flavor at the time of decay is determined with a tagging algorithm that exploits the correlation between the flavor of the b quark and the charges of its decay products. The lifetime and oscillation frequencies are measured simultaneously with an unbinned maximum-likelihood fit that uses, for each event, the measured difference in decay times of the two B mesons (Δt), the calculated uncertainty on Δt, the signal and background probabilities, and b-quark tagging information for the other B. The results are τB0=(1.523-0.023+0.024±0.022) ps and Δmd=(0.492±0.018 ±0.013) ps-1. The statistical correlation coefficient between τB0 and Δm d is -0.22.