Georg Viehhauser

Abstract:

We report the results of a search for the rare baryonic decay modes B0→ΛΛ̄, B+→Λ̄p, B0→Λ̄pπ-, and B0→pp̄ (and their charge conjugate states) using 5.8 × 106 BB̄ pairs collected with the CLEO detector. We see no statistically significant signals in any of these modes and set 90% confidence level upper limits on their branching fractions, B(B0→ΛΛ̄)<3.9 × 10-6, B(B+→Λ̄p)<2.6 × 10-6, B(B0→Λ̄pπ-)<1.3 × 10-5 and B(B0→pp̄)<7.0 × 10-6. ©1999 The American Physical Society.

Abstract:

We have searched for five decay modes of the τ lepton that simultaneously violate lepton and baryon number: τ-→p̄γ, τ-→p̄π0, τ-→p̄η, τ-→p̄2π0, and τ-→p̄π0η. The data used in the search were collected with the CLEO II detector at the Cornell Electron Storage Ring. The integrated luminosity of the data sample is 4.7 fb-1, corresponding to the production of 4.3 × 106 τ+τ- events. No evidence is found for any of the decays, resulting in much improved upper limits on the branching fractions for the two-body decays and first upper limits for the three-body decays. ©1999 The American Physical Society.

Abstract:

Using a 4.19 fb-1 data sample collected with the CLEO II detector at the Cornell Electron Storage Ring, we have searched for dipion transitions between pairs of Y resonances at center of mass energies Ec.m. = 10.58 GeV and Ec.m. = 10.52GeV. We obtain the 90% confidence level upper limits B(Υ(4S) →Υ (2S) π+π-)<3.9×10-4 and B(Υ(4S)→Υ(1S)π+π -)<1.2×10-4. We also observe the transitions Υ(2S)→Υ(1S)π+π-, Υ(3S)→Υ(2S)π+π-, and Υ(2S)→Υ(1S)π+π-, from which we measure the cross sections for the radiative processes e+e-→Υ(2S)γ and e+e-→Υ(2S)γ. We obtain σee→Υ(3S)γ = (17.8±3.0±1.7)pb and ee→Υ(2S)γ = (15.5±1.3±1.4) pb at Ec.m. = 10.58 GeV, and ee→Υ(3S)γ = (27.3 ±5.0±2.6) pb and ee→Υ(2S)γ = (16.3±1.8±1.5) pb at Ec.m. = 10.52 GeV, which we compare with theoretical predictions. ©1999 The American Physical Society.