Georg Viehhauser

Abstract:

Based on a high statistics e⁺e^-→cc̄ data sample, we report on the inclusive rate for charmed baryons to decay into Λ particles using charm-event tagging. We select e⁺e^-→cc̄ events which have a clear anti-charm tag and measure the Λ content in the hemisphere opposite the tag (charge conjugate modes are implicit). This allows us to determine the product branching fraction BΛ=B(c→ΘcX)XB(Θ c→ΛX), where Θc represents a sum over all charmed baryons produced in e⁺e^- fragmentation at √s=10.5 GeV, given our specific tags. We obtain BΛ=(1.87±0.03±0.33)%. ©2000 The American Physical Society.

Abstract:

We search for the decay of the B⁰ meson into a pair of leptons in the suppressed channels B⁰→e⁺e^-, B⁰→μ⁺μ^- and in the lepton number violating channel B⁰→e^±μ^∓ in a sample of 9.7×10⁶ BB̄ pairs recorded by CLEO detector. No signal is found, and the following upper limits on the branching fractions are established: B(B⁰→e⁺e^-)<8.3×10^-7, B(B⁰→μ⁺μ^-)<6.1×10 ^-7, B(B⁰→e^±μ ^∓)<15×10^-7 at 90% confidence level. A new lower limit on the Pati-Salam leptoquark mass MLQ>27 TeV is established at 90% confidence level. © 2000 The American Physical Society.

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.