Measurement of the B-s(0) lifetime and study of B-s(0)-(B-s(0))over-bar oscillations using D(s)l events

Lifetime and oscillations of B-s(0) mesons have been studied in events with a large transverse momentum lepton and a D-s of opposite electric charge in the same hemisphere, selected from about 3.6 million hadronic Z(0) decays accumulated by DELPHI between 1992 and 1995. The B-s(0) lifetime and the fractional width difference between the two physical B-s(0) states have been found to be: tau(Bs0) = (1.42(-0.13)(+0.14)(stat.) +/- 0.03(syst)) ps Delta Gamma(Bs0) /Gamma(Bs0) < 0.46 at the 95% C.L. In the latter result it has been assumed that tau(Bs0) = tau(Bd0). Using the same sample, a limit on the mass difference between the physical B-s(0) states has been set: Delta m(Bs0) > 7.4 ps(-1) at the 95% C.L. with a corresponding sensitivity equal to 8.1 ps(-1).