Updated measurements of the B-0 and B+ meson lifetimes are presented.
From a data sample of 1.72 million hadronic Z(0) decays recorded durin
g the period 1991 to 1993, a sample of approximately 1000 semileptonic
B meson decays containing a D-0, D+ or D+ has been isolated. From th
e distribution of decay times in the different samples the lifetimes o
f the B-0 and B+ mesons are determined to be 1.53 +/- 0.12 +/- 0.08 ps
and 1.52 +/- 0.14 +/- 0.09 ps, respectively, where the first error is
statistical and the second systematic. The ratio of the B+ to BO life
times is measured to be 0.99 +/- 0.14-(+0.05)(0.04), confirming expect
ations that the lifetimes are similar.