Search for {\rm B_s}^0 oscillations using inclusive lepton events

A search for oscillations is performed using a sample of semileptonic b-hadron decays collected by the ALEPH experiment during 1991–95. Compared to previous inclusive lepton analyses, the proper time resolution and b-flavour mistag rate are significantly improved. Additional sensitivity to mixing is obtained by identifying subsamples of events having a purity which is higher than the average for the whole data sample. Unbinned maximum likelihood amplitude fits are performed to derive a lower limit of at the 95% confidence limit (95% CL). Combining with the ALEPH -based analyses yields at 95% CL. Received: 20 July 1998 / Published online: 19 February 1999