Author/Authors :
DELPHI Collaboration، نويسنده , , P. Abreu، نويسنده , , W. Adam، نويسنده , , T. Adye، نويسنده , , E. Agasi، نويسنده , , I. Ajinenko، نويسنده , , R. Aleksan، نويسنده , , G.D. Alekseev، نويسنده , , P.P. Allport، نويسنده , , S. Almehed، نويسنده , , F.M.L. Almeida، نويسنده , , S.J. Alvsvaag، نويسنده , , U. Amaldi، نويسنده , , A. Andreazza، نويسنده , , P. Antilogus، نويسنده , , W-D. Apel، نويسنده , , R.J. Apsimon، نويسنده , , Y. Arnoud، نويسنده , , B. ?sman، نويسنده , , J-E. Augustin، نويسنده , , et al.، نويسنده ,
Abstract :
J/ψ mesons have been reconstructed from their decay to μ+μ− and e+e−, using the data collected by the DELPHI experiment during 1991 and 1992 at the LEP collider. From about 1 million hadronic Z decays 153 ± 17 J/ψ were found, 5.4 ± 2.3 ψ′ were obtained in the channel J/ψ (→μ+μ−)π+π− and 6.4 ± 2.7 χc in the channel J/ψ ( → μ+μ−)γ. As the dominant source of Jψ mesons is from bquarks, the following branching ratios: Br(b → J/ψ X) = (1.12 ± 0.12 (stat) ± 0.10 (syst.))%, Br(b → ψ′ X) = (0.48 ± 0.22 (stat.± 0.10 (syst.))%, Br(b → χc1 X) = (1.4 ± 0.6 (stat.)−0.2+0.4 (syst.))% were measured. From the proper time distribution of the J/ψ sample, the average lifetime of b-hadrons decaying into J/ψ was found to be: τB = 1.50−0.21+0.24 (stat.) ± 0.03 (syst.) ps. A search for completely reconstructed B meson decays to final states including a J/ψ gave a signal of 15 ± 5 events.
