Measurement of Ds+ meson production in Z decays and of the Bs0 lifetime

Sezione di Bari Istituto Nazionale di Fisica Nucleare
Service de Physique des Particules
Santa Cruz Institute for Particle Physics
University of Wisconsin Madison
Johannes Gutenberg Universität Mainz
Scuola Normale Superiore di Pisa
Institute of High Energy Physics Chinese Academy of Science
University of Edinburgh
IN2P3 Institut National de Physique Nucleaire et de Physique des Particules
Universität Siegen
Lancaster University
Rutherford Appleton Laboratory
Università degli Studi di Firenze
Universitat Autònoma de Barcelona
Royal Holloway University of London
Consiglio Nazionale delle Ricerche
Université de la Méditerranée Aix-Marseille II
European Organization for Nuclear Research
Niels Bohr Institute
Università degli Studi di Trieste

Abstract

The lifetime of the Bs0 meson is measured in approximately 3 million hadronic Z decays accumulated using the ALEPH detector at LEP from 1991 to 1994. Seven different Ds− decay modes were reconstructed and combined with an opposite sign lepton as evidence of semileptonic Bs0 decays. Two hundred and eight Ds−ℓ+ candidates satisfy selection criteria designed to ensure precise proper time reconstruction and yield a measured Bs0 lifetime of τ(Bs0) = 1.59−0.15+0.17 (stat) ±0.03 (syst) ps. Using a larger, less constrained sample of events, the product branching ratio is measured to be Br(b→Bs0) ·Br(Bs0→Ds−ℓ+νX) = 0.82 ± 0.09 (stat) −0.14+0.13 (syst) %.