Study of B0s oscillations and lifetime using fully reconstructed D̄s decays

A search for B0s oscillations is performed using approximately 4 million Z → qq̄ events collected by the ALEPH experiment during 1991-1995. B0s candidates are partially reconstructed by combining tracks with fully reconstructed D-s candidates. The B0s production flavour is estimated from the sign of the opposite hemisphere charge, a fragmentation kaon in the same hemisphere, or a lepton in the opposite hemisphere. From a total sample of 1620 candidates, with a B0s purity estimated to be 22%, all values of Δms below 3.9 ps-1 and between 6.5 and 8.8 ps-1 are excluded at 95% CL. From the same sample, the B0s lifetime is measured to be τs = 1.47 ± 0.14(stat) ± 0.08(syst) ps. This analysis selects mainly hadronic B0s decays and is statiscally independent of a previous ALEPH analysis selecting B0s → D(*)-s ℓ+ v candidates. Combining these two analyses yields Δms > 7.9 ps-1 at 95% CL and τs = 1.51 ± 0.11 ps.