Study of the B-s(0)(B)over-bar(s)(0) oscillation frequency using D(s)(-)l(+) combinations in Z decays

A lower limit on the oscillation frequency of the <B-s(0)(B)over bar (0)(s)> 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 <B-s(0)(B)over bar (0)(s)> 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. RI ANTONELLI, ANTONELLA/C-6238-2011; Passalacqua, Luca/F-5127-2011; Murtas, Fabrizio/B-5729-2012; St.Denis, Richard/C-8997-2012; Sanchez, Federico/F-5809-2012; Forti, Francesco/H-3035-2011; Ferrante, Isidoro/F-1017-2012