Simultaneous measurement of the B 0 meson lifetime and mixing frequency with B 0 \ D * (cid:192) ł ¿ n ł decays

We measure the B 0 lifetime t B 0 and the B 0 - B¯ 0 oscillation frequency D m d with a sample of approximately 14000 exclusively reconstructed B 0 ! D * 2 , 1 n , signal events, selected from 23 million BB¯ pairs recorded at the Y (4 S ) 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 ( D t ), the calculated uncertainty on D t , the signal and background probabilities, and b -quark tagging information for the other B . The results are t B 0 5 (1.523 2 0.023 1 0.024 6 0.022) ps and D m d 5 (0.492 6 0.018 6 0.013) ps 2 1 . The statistical correlation coefficient between t B 0 and D m d is 2 0.22.