Georg Viehhauser

Abstract:

We have observed new channels for τ decays with an η in the final state. We study 3-prong tau decays, using the η → γγ and η → 3π⁰ decay modes and 1-prong decays with two π⁰’s using the η → γγ channel. The measured branching fractions are B(τ → π⁻π⁻π⁺ηντ = (3.4^+0.6-0.5 ± 0.6) × 10^-4 and B(τ⁻ → π⁻2π⁰ηντ = (1.4 ± 0.6 ± 0.3) × 10^-4. We observe clear evidence for f1 → ηππ substructure and measure B(τ⁻ → f1π⁻ντ) = (5.8^+1.4-1.3 ± 1.8) × 10^-4. We have also searched for η′(958) production and obtain 90% C.L. upper limits B(τ → π⁻η′ντ) < 7.4 × 10^-5 and B(τ → π⁻π⁰η′ντ) < 8.0 × 10^-5. © 1997 American Physical Society.

Abstract:

Using 4.8 fb^-1 of data taken with the CLEO II detector, the branching fraction for the Cabibbo suppressed decay D⁺ → π⁰ℓ⁺v measured relative to the Cabibbo favored decay D⁺ → K⁰̄ℓ⁺v is found to be 0.046 ± 0.014 ± 0.017. Using Vcs and Vcd from unitarity constraints, we determine |f^π+(0) / f^K+(0)|² = 0.9 ± 0.3 ± 0.3 We also present a 90% confidence level upper limit for the branching ratio of the decay D⁺ → ηe⁺ve relative to that for D⁺ →⁰e⁺ve of 1.5. © 1997 Published by Elsevier Science B.V.

Abstract:

We have measured the spectral shape Michel parameters ρ and η using leptonic decays of the τ, recorded by the CLEO II detector. Assuming e - μ universality in the vectorlike couplings, we find ρeμ = 0.735 ± 0.013 ± 0.008, where the first error is statistical and the second systematic. We also present measurements for the parameters for e and μ final states separately. © 1997 The American Physical Society.

Abstract:

We have made a first measurement of the lepton momentum spectrum in a sample of events enriched in neutral B's through a partial reconstruction of B⁰ → D*^- l⁺v̄. This spectrum, measured with 2.38 fb^-1 of data collected at the Y(4S) resonance by the CLEO II detector, is compared directly to the inclusive lepton spectrum from all Y(4S) events in the same data set. These two spectra are consistent with having the same shape above 1.5 GeV/c. From the two spectra and two other CLEO measurements, we obtain the B⁰ and B⁺ semileptonic branching fractions, b0 and b+, their ratio, and the production ratio f+-/f00 of B⁺ and B⁰ pairs at the Y(4S). We report b+/b0 = 0.950^+0.117-0.080 ± 0.091, b0 = (10.78 ± 0.60 ± 0.69)%, and b+ = (10.25 ± 0.57 ± 0.65)%. b+/b0 is equivalent to the ratio of charged to neutral B lifetimes, τ+/τ0. © 1997 Published by Elsevier Science B.V.