Showing papers by "L. Köpke published in 1988"
TL;DR: A revised determination of charmed--D-meson absolute branching fractions based on complete reconstruction of DD-bar events at the psi(3770) is reported, unable to account fully for a reported deficit in charm production in B- Meson decay.
Abstract: We report a revised determination of charmed--D-meson absolute branching fractions based on complete reconstruction of DD-bar events at the psi(3770). Two backgrounds, Cabibbo-suppressed and multi-..pi../sup 0/D decays, are addressed in detail. The first measurement of the decay D/sup 0/..-->..K/sup -/..pi../sup +/..pi../sup 0/..pi../sup 0/ establishes the sensitivity to hitherto unobserved multi-..pi../sup 0/ modes. Removal of both backgrounds reduces the values of our previously reported branching fractions by (21--24)% leaving their ratios largely unchanged. The new values are unable to account fully for a reported deficit in charm production in B-meson decay.
147 citations
TL;DR: In this article, the authors reported the results of a search for the leptonic decay D/sup+/..--> mu../sup +/..nu../sub..mu../ using the Mark III detector at the SLAC e/sup + /e/sup -/ storage ring SPEAR.
Abstract: We report the results of a search for the leptonic decay D/sup +/..--> mu../sup +/..nu../sub ..mu../ using the Mark III detector at the SLAC e/sup +/e/sup -/ storage ring SPEAR. A data sample of 9.3 pb/sup -1/ collected at the psi(3770) resonance yields no signal events, corresponding to a 90%-confidence-level upper limit of 7.2 x 10/sup -4/ on the branching ratio B(D/sup +/..--> mu../sup +/..nu../sub ..mu../). This represents an upper limit on the pseudoscalar decay constant f/sub D/ of 290 MeV/c/sup 2/.
37 citations
TL;DR: In this article, a new measurement of the D∗ branching ratio was reported, using data obtained with the Mark III detector at the e^+e^− storage ring SPEAR at s=4.14GeV.
18 citations
TL;DR: The τ lifetime has been measured with the OPAL detector at LEP, from analyses using the impact parameters in decays to single charged tracks, and the decay lengths from τ decay to three charged tracks as mentioned in this paper.
Abstract: The τ lifetime has been measured with the OPAL detector at LEP, from analyses using the impact parameters in decays to single charged tracks, and the decay lengths from τ decays to three charged tracks. The 1991 sample of approximately 12300 τ-pair events, of which 70% contain silicon microvertex detector information, has been combined with a re-analysis of the 5100 events recorded during 1990. The two statistically-independent determinations give:
$$\begin{gathered} \tau (one - prong) = 296.4 \pm 7.1 (stat) \pm 3.8 (sys) fs, \hfill \\ \tau (three - prong) = 286.3 \pm 7.4 (stat) \pm 5.2 (sys) fs. \hfill \\ \end{gathered} $$
The weighted average of these results after combination of the uncorrelated systematic errors is:
$$\tau _\tau = 291.9 \pm 5.1 (stat) \pm 3.1 (sys) fs.$$
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14 citations
TL;DR: In this article, a search for the decay D/sup 0/..-->..e/sup +/e/e /sup -/ -/ based on a data sample of 9.6 pb/sup -1/ collected at the psi(3770) resonance with the Mark III detector at the SLAC e/sup+ /e /e//sup-/ storage ring SPEAR was performed and no evidence for this flavor-changing weak neutral-current decay was found.
Abstract: We report a search for the decay D/sup 0/..-->..e/sup +/e/sup -/ based on a data sample of 9.6 pb/sup -1/ collected at the psi(3770) resonance with the Mark III detector at the SLAC e/sup +/e/sup -/ storage ring SPEAR. We find no evidence for this flavor-changing weak-neutral-current decay and set an upper limit on the branching ratio of B(D/sup 0/..-->..e/sup +/e/sup -/)<1.3 x 10/sup -4/ at the 90% confidence level. This limit constrains various extensions of the standard model.
7 citations