Georg Viehhauser

Abstract:

Using 4.68 fb(-1) of e(+)e(-) annihilation data collected with the CLEO II detector at the Cornell Electron Storage Ring, we have studied tau radiative decays tau(-)-->nu(tau)&mgr;(-)nu;(&mgr;)gamma and tau(-)-->nu(tau)e(-)nu;(e)gamma. For a 10 MeV minimum photon energy in the tau rest frame, the branching fraction for radiative tau decay to a muon or electron is measured to be (3.61+/-0.16+/-0. 35)x10(-3) or (1.75+/-0.06+/-0.17)x10(-2), respectively. The branching fractions are in agreement with standard model theoretical predictions.

Abstract:

We have used the CLEO II detector to study the multiplicity of charged particles in the decays of B mesons produced at the (Formula presented) resonance. Using a sample of (Formula presented) B meson pairs, we find the mean inclusive charged particle multiplicity to be (Formula presented) for the decay of the pair. This corresponds to a mean multiplicity of (Formula presented) for a single B meson. Using the same data sample, we have also extracted the mean multiplicities in semileptonic and nonleptonic decays. We measure a mean of (Formula presented) charged particles per (Formula presented) decay when both mesons decay semileptonically. When neither B meson decays semileptonically, we measure a mean charged particle multiplicity of (Formula presented) per (Formula presented) pair. © 2000 The American Physical Society.

Abstract:

We present the first observation of the decay B →J/ψϕK Using 9.6 ×106BB¯meson pairs collected with the CLEO detector, we have observed ten fully reconstructed B →J/ψϕK candidates, whereas the estimated background is 0.5 ±0.2event. We obtain a branching fraction of B(B →J/ψϕK)=(8.8−3.0+3.5[stat]±1.3[syst])×10−5This is the first observed B meson decay requiring the creation of an additional ss¯quark pair. © 2000 The American Physical Society.

Abstract:

Based on a sample corresponding to 4.3×106 produced τ-pair events, we have studied hadronic dynamics in the decay τ-→ντπ-π 0π0 in data recorded by the CLEO II detector operating at the CESR e+e- collider. The decay is dominated by the process τ-→ντa1-(1260), with the a1- meson decaying to three pions predominantly via the lowest dimensional (mainly S-wave) ρ-π0 Born amplitude. From model-dependent fits to the Dalitz plot and angular observables in bins of 3 π mass, we find significant additional contributions from amplitudes for a1 decay to σπ, f0(1370)π, and f2(1270)π, as well as higher dimensional a1→ρπ and ρ′ π amplitudes. Notably, the squared σπ amplitude accounts for approximately 15% of the total τ- →ντπ-π0π0 rate in the models considered. The data are well described using couplings to these amplitudes that are independent of the 3π mass. These amplitudes also provide a good description for the τ- →ντπ-π0π0 Dalitz plot distributions. We have searched for additional contributions from τ-→ντπ′ -(1300). We place 90% confidence level upper limits on the branching fraction for this channel of between 1.0×10-4 and 1.9×10-4, depending on the π′ decay mode considered. The π-π0π0 mass spectrum is parametrized by a Breit-Wigner form with a mass-dependent width which is specified according to the results of the Dalitz plot fits plus an unknown coupling to an a1→K*K amplitude. From a χ2 fit using this parametrization, we extract the pole mass and width of the a1, as well as the magnitude of the K*K coupling. We have also investigated the impact of a possible contribution from the a1′(1700) meson on this spectrum. Finally, exploiting the parity-violating angular asymmetry in a1→3π decay, we determine the signed value of the τ neutrino helicity to be hντ=-1.02±0.13 (stat)±0.03 (syst+model), confirming the left-handedness of the τ neutrino. ©1999 The American Physical Society.

Abstract:

From a data sample of 29058 τ+→π±π+π -π0ντdecays observed in the CLEO detector we derive a 95% confidence upper limit on the tau neutrino mass of 28 MeV. ©2000 The American Physical Society.