Eur. Phys. J. C 29, 143-170 (2003)
DOI: 10.1140/epjc/s2003-01230-5

Improved search for oscillations

The ALEPH Collaboration

(Received: 21 February 2003 / Published online: 11 June 2003)

Abstract
An improved search for B_s oscillations is performed in the ALEPH data sample collected during the first phase of LEP, and reprocessed in 1998. Three analyses based on complementary event selections are presented. First, decays of B_s mesons into hadronic flavour eigenstates are fully reconstructed. This selection yields a small sample of candidates with excellent decay length and momentum resolution and high average B_s purity. Semileptonic decays with a reconstructed D_s^- meson provide a second sample with larger statistics, high average B_s purity, but a poorer momentum and decay length resolution due to the partial decay reconstruction. Finally, semileptonic b-hadron decays are inclusively selected and yield the data sample with the highest sensitivity to B_s oscillations, as the much higher statistics compensate for the low average B_s purity and poorer time resolution. A lower limit is set at at , significantly lower than the expected limit of .

© Società Italiana di Fisica, Springer-Verlag 2003