Georg Viehhauser

Abstract:

Using a sample of 9.6 × 10⁶BB̄ meson pairs collected with the CLEO detector, we have fully reconstructed 135 B⁰→ψ^(′)KS⁰ and 526 B⁺→ψ^(′)K⁺ candidates with very low background. We fitted the ψ^(′)K invariant mass distributions of these B meson candidates and measured the masses of the neutral and charged B mesons to be M(B⁰)=5279.1±0.7[stat]±0.3[ syst] MeV/c² and M(B⁺)=5279.1±0.4[stat]±0.4[ syst] MeV/c². The precision is a significant improvement over previous measurements. ©2000 The American Physical Society.

Abstract:

The electron storage ring CESR at Cornell University is presently undergoing a major upgrade together with its B-physics detector CLEO. Improved focusing and superconducting cavities will increase the luminosity of the collider to more than 2 x 10(33) cm(2) s(-1). To accommodate the necessary accelerator elements the tracking region of CLEO has to be rebuilt. The new tracking system consists of a four-layer silicon vertex detector and a large volume drift chamber, which also provides dE/dx particle identification information. The CLEO III upgrade also includes a new particle identification system which allows full exploitation of the possibilities provided by the upgraded accelerator. This PID system is a proximity focusing RICH with lithium fluoride radiators and multi-wire chambers filled with a methane/triethylamine mixture to detect UV Cherenkov photons. Installation of the new detector elements in the CLEO detector is taking place during summer 1999. (C) 2000 Elsevier Science B.V. All rights reserved.

Abstract:

We report results of a search for the rare radiative decay B̄0 → D0γ. Using 9.66 × 10 6 BB̄ meson pairs collected with the CLEO detector at the Cornell Electron Storage Ring, we set an upper limit on the branching ratio for this decay of 5.0× 10-5 at 90% C.L. This provides evidence that the anomalous enhancement is absent in W-exchange processes and that weak, radiative B decays are dominated by the short-distance b → sγ mechanism in the standard model. © 2000 The American Physical Society.

Abstract:

The resonant structure of the four pion final state in the decay τ→3ππ⁰ντ has been analyzed using 4.27 million τ⁺τ^- pairs collected by the CLEO II experiment at the Cornell Electron Storage Ring. A partial wave analysis of the resonant structure of the ô-»3 τ→3ππ⁰ντ decay has been performed; the spectral decomposition of the four pion system is dominated by the ωπ and a1π final states. The mass and width of the ρ′ resonance have been extracted from a fit to the τ→ωπντ spectral function. We have searched for second class currents in the decay τ→ωπντ using spin-parity analysis and established an upper limit on the non-vector current contribution. ©2000 The American Physical Society.

Abstract:

We present an update of the search for the lepton family number violating decay τ→μγ using 12.6 million τ⁺τ^- pairs collected with the CLEO detector. No evidence of a signal has been found and the corresponding upper limit is script B sign(τ→μγ)<1.1×10^-6 at 90% C.L., significantly smaller than previous experimental limits. ©2000 The American Physical Society.