Study of B_S~0 oscillations and lifetime using fully reconstructed D_S~- decays

摘要

A search for B_s~0 oscillations is performed using approximately 4 million Z → qq-bar events collected by the ALEPH experiment during 1991-1995. B_s~0 candidates are partialy reconstructed by combining tracks with fully reconstructed D_s~- candidates. The B_s~0 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 B_s~0 purity estimated to be 22%, all values of Δm_s below 3.9 ps~(-1) ad between 6.5 and 8.8 ps~(-1) are excluded at 95% CL. From the same sample, the B_s~0 lifetime is measured to be τ_s = 1.47 ± 0.14(stat) ± 0.08(syst) ps. This analysis selects mainly hadronic B_s~0 decays and is statistically independent of a previous ALEPH analysis selecting B_s~0 → D_s~((*)-) l~+υ candidates. Combining these two analyses yields Δm_s > 7.9 ps~(-1) at 95% CL and τ_s = 1.51 ± 0.11 ps.