Buskulic, D (reprint author), INST NATL PHYS NUCL & PHYS PARTICULES, CNRS, PHYS PARTICULES LAB, F-74019 ANNECY LE VIEUX, FRANCE.
A lower limit on the oscillation frequency of the system is obtained from approximately four million hadronic Z decays accumulated using the ALEPH detector at LEP from 1991 to 1995. Leptons are combined with opposite sign D-s(-) candidates reconstructed in seven different decay modes as evidence of semileptonic B-s(0) decays. Criteria designed to ensure precise proper time reconstruction select 277 D(s)(-)l(+) combinations. The initial state of these B-s(0) candidates is determined using an algorithm optimized to efficiently utilise the tagging information available for each event. The limit at 95% confidence level on the oscillation frequency is Delta m(s) > 6.6 ps(-1). The same data is used to update the measurement of the B-s(0) lifetime, tau(s) = 1.54(-0.13)(0.14) (stat) +/- 0.04 (syst) ps.