A study of B meson oscillations using dilepton events

The time dependence of B meson oscillations is studied using hadronic Z0 decays with identified leptons in both thrust hemispheres. Decay times are reconstructed for each of the semileptonic B decays by forming vertices which include the lepton and by estimating the B meson momentum. The mass difference of the two mass eigenstates in the B0d system, Δmd, is measured to be 0.462+0.040+0.052-0.053-0.035 ps-1, where the first error is statistical and the second systematic. For the B0s system, a lower limit of Δms > 2.2 ps-1 at 95% C.L. is derived. (orig.)