Search for B0s oscillations using inclusive lepton events

TL;DR

This paper reports a search for B0s meson oscillations using inclusive lepton events, achieving improved time resolution and flavor tagging, setting a lower limit on the oscillation frequency with combined analyses.

Contribution

It introduces enhanced techniques for measuring B0s oscillations, including better proper time resolution and flavor mistag reduction, and combines multiple analyses for stronger limits.

Findings

Lower limit on Deltam_s > 9.6 ps^-1 at 95% CL

Improved proper time resolution and b-flavour mistag rate

Enhanced sensitivity through subsample identification

Abstract

A search for B0s oscillations is performed using a sample of semileptonic b-hadron decays collected by the ALEPH experiment during 1991-1995. Compared to previous inclusive lepton analyses, the proper time resolution and b-flavour mistag rate are significantly improved. Additional sensitivity to B0s mixing is obtained by identifying subsamples of events having a B0s 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 Deltam_s>9.5ps^-1 at 95% CL. Combining with the ALEPH D-s based analyses yields Deltam_s>9.6ps^-1 at 95% CL.