Georg Viehhauser

Abstract:

Using 13.4 fb(-1) of data collected with the CLEO detector at the Cornell Electron Storage Ring, we have observed 300 events for the two-photon production of ground-state pseudoscalar charmonium in the decay eta(c)-->K(0)(S)K-/+pi(+/-). We have measured the eta(c) mass to be [2980.4+/-2.3 (stat)+/-0.6 (syst)] MeV and its full width as [27.0+/-5.8 (stat)+/-1.4 (syst)] MeV. We have determined the two-photon partial width of the eta(c) meson to be [7.6+/-0.8 (stat)+/-0.4 (syst)+/-2.3 (br)] keV, with the last uncertainty associated with the decay branching fraction.

Abstract:

We report results of searches for charmless hadronic B meson decays to pseudoscalar( pi(+/-), K+/-, pi(0), or K(0)(S))-vector( rho, K(*), or omega) final states. By using 9.7x10(6) BB pairs collected with the CLEO detector, we report the first observation of B(-)--->pi(-)rho(0), B(0)-->pi(+/-)rho(-/+), and B(-)-->pi(-)omega, which are expected to be dominated by hadronic b-->u transitions. The measured branching fractions are (10.4(+3.3)(-3.4)+/-2.1)x10(-6), (27.6(+8.4)(-7.4)+/-4.2)x10(-6), and (11.3(+3.3)(-2.9)+/-1. 4)x10(-6), respectively. Branching fraction upper limits are set for all of the other decay modes investigated.

Abstract:

The Λc⁺→pK^-π⁺ yield has been measured in a sample of two-jet continuum events containing both a charm tag ("D̄") as well as an antiproton (e⁺e^-→D̄p̄X), with the antiproton in the hemisphere opposite the D̄ (measurement of charge conjugate modes is implicit throughout). Under the hypothesis that such selection criteria tag e⁺e^-→D̄p̄Λc⁺X events, the Λc⁺→pK^-π⁺ branching fraction can be determined by measuring the pK^-π⁺ yield in the same hemisphere as the antiprotons in our D̄p̄X sample. Three types of D charm tags are used, πsoft^- (from D*^-→D̄⁰πsoft^-), electrons (from D̄→Xe^-v), and fully reconstructed D̄⁰→K⁺π^- or D^- →K⁺π^-π^- or Ds^-→φπ^-. Combining our results obtained from the three independent charm tags, we obtain B(Λc⁺→pK^-π ⁺)=(5.0±0.5±1.2)%. ©2000 The American Physical Society.

Abstract:

A study of charm fragmentation into Ds*⁺ and Ds⁺ in e⁺e^- annihilations at √s=10.5 GeV is presented. This study using 4.72±0.05 fb^-1 of CLEO II data reports measurements of the cross sections σ(Ds*⁺) and σ(Ds⁺) in momentum regions above x=0.44, where x is the Ds momentum divided by the maximum kinematically allowed Ds momentum. The Ds vector to vector plus pseudoscalar production ratio is measured to be PV(x(Ds⁺)>0.44)=0.44±0.04. ©2000 The American Physical Society.

Abstract:

Using a sample of 4.7 fb^-1 integrated luminosity accumulated with the CLEO II detector at the Cornell Electron Storage Ring (CESR), we investigate the mass spectrum and resonant structure in τ^- →Κ^-π⁺π^-ντ decays. We measure the relative fractions of Κ1(1270) and Κ1(1400) resonances in these decays, as well as the Κ1 masses and widths. Our fitted Κ1 resonances are somewhat broader than previous hadroproduction measurements, and in agreement with recent CERN LEP results from tau decay. The larger central value of our measured width supports models which attribute the small τ^-→Κ^-π⁺π ^-ντ branching fraction to larger Κ1 widths than are presently tabulated. We also determine the Κa-Κb mixing angle θΚ. ©2000 The American Physical Society.