Measurement of the B0 and B− meson lifetimes

Abstract The lifetimes of the B 0 and B − mesons are measured using a sample of about four million hadronic Z decays collected from 1991 to 1995 with the Aleph detector at LEP. The data sample has been recently reprocessed, achieving a substantial improvement in the tracking performance. Semileptonic decays of B 0 and B − mesons are partially reconstructed by identifying events containing a lepton with an associated D ★+ or D 0 meson. The proper time of the B meson is estimated from the measured decay length and the momentum of the D -lepton system. A fit to the proper time of 1880 D ★+ l − and 2856 D 0 l − candidates yields the following results: τ B 0 =1.518±0.053±0.034  ps , τ B − =1.648±0.049±0.035 ps, τ B − /τ B 0 =1.085±0.059±0.018 .