BUSKULIC, D (reprint author), CNRS, IN2P3, PHYS PARTICULES LAB, F-74019 ANNECY LE VIEUX, FRANCE.
The lifetimes of the B0BAR and B- mesons have been measured with the ALEPH detector at LEP. Semileptonic decays of B0BAR and B- mesons were partially reconstructed by identifying events containing a lepton with an associated D*+ or D0 meson. The proper time of the B meson was estimated from the measured decay length and the momentum and mass of the D-lepton system. A fit to the proper time of 77 D*+l- and 77 D0l- candidates, combined with a constraint on the lifetime ratio (tau-/tau0) arising from the relative rates of observed D*+l- and D0l- events, yielded the following lifetimes: tau0 = 1.52(+0.20/-0.18) (stat. )+0.07/-0.13 (syst.) ps, tau = 1.47(+0.22/-0.19) (stat.)+0.15/-0.14 (syst.) ps, tau-/tau0 = 0.96(+0.19/-0.15) (stat. )+0.18/-0.12(syst.).