B. Gittelman

First measurement of Γ(D* +) and precision measurement of m D*+-m D0

We present the first measurement of the D*+ width using 9/fb of e+ e- data collected near the Upsilon(4S) resonance by the CLEO II.V detector. Our method uses advanced tracking techniques and a reconstruction method that takes advantage of the small vertical size of the CESR beam spot to measure the energy release distribution from the D*+ -> D0 pi+ decay. We find Gamma(D*+) = 96 +- 4 (Statistical) +- 22 (Systematic) keV. We also measure the energy release in the decay and compute Delta m = m(D*+) - m(D0) = 145.412 +- 0.002 (Statistical) +- 0.012 (Systematic) MeV/c^2

The CLEO detector

Abstract The construction and performance of a large aperture magnetic detector designed for use at the Cornell Electon Storage Ring is descr bed.

Tests of cesium iodide crystals for an electromagnetic calorimeter

Abstract A new electromagnetic shower detector will be constructed for the CLEO II experiment at CESR. It will consist of 8000 CsI(Tl) crystals coupled to solid state photodiodes. Extensive tests on the response of 175 CsI crystals are reported here. Each block measured 5 cm by 5 cm in cross section and 30 cm (16.2 radiation lengths) in depth. A fast and reliable method to determine acceptable light output and uniformity of crystals using a 137Cs radioactive source and photomultiplier readout was successfully developed. For test beam studies each crystal was equipped with four silicon photodiodes connected to a low-noise charge amplifier. Calibration with a positron test beam yielded average light output of 2500 photoelectrons per MeV and showed good correlation with the radioactive source exposures. In the beam tests at 180 (5000) MeV, energy resolutions of 4% (1.5%) and position resolutions transverse to the beam of 1.2 (0.3) cm were achieved. The effects of material between and in front of crystals, non-normal incidence, and staggering of adjacent crystals were studied, and together were found to degrade the energy resolution by only a modest amount. Operation of the system near room temperature will ensure low noise and stable response. The radiation sensitivity of a number of CsI blocks was measured and found to be acceptable for the radiation levels anticipated in CLEO II.

Branching fractions of τ Leptons to three charged Hadrons

From electron-positron collision data collected with the CLEO detector operating at Cornell Electron Storage Ring near sqrt[s]=10.6 GeV, improved measurements of the branching fractions for tau decays into three explicitly identified hadrons and a neutrino are presented as B(tau(-)-->pi(-)pi(+)pi(-)nu(tau))=(9.13+/-0.05+/-0.46)%, B(tau(-)-->K-pi(+)pi(-)nu(tau))=(3.84+/-0.14+/-0.38) x 10(-3), B(tau(-)-->K-K+pi(-)nu(tau))=(1.55+/-0.06+/-0.09) x 10(-3), and B(tau(-)-->K-K+K-nu(tau))<3.7 x 10(-5) at 90% C.L., where the uncertainties are statistical and systematic, respectively.

Limits on rare exclusive decays of B mesons

Abstract We have set upper limits for rare exclusive decays of B mesons arising from higher order processes in the standard model of electroweak interactions. Such decays may occur via “penguin diagrams” in B decay. We also set an upper limit on a lepton-number-violating decay mode of the neutral B meson.

A search for exclusive penguin decays of B mesons

Abstract We have measured upper limits on branching fractions for rare exclusive decays of B mesons arising from one-loop diagrams in the standard model of electroweak interactions. We also obtain an upper limit for the lepton-number-violating decay B 0 → μ ± e ∓ .

Measurement of the isospin mass splitting Ξ+cΞ0c

Abstract Using the CLEO detector, we present a measurement of the mass of the charged charmed strange baryon Ξ + c and its neutral counterpart the Ξ 0 c . The Ξ + c is observed through its decay to Ξ - π + π + , and its mass is measured to be (2467±3±4) MeV. The isospin mass splitting of the Ξ c system is found to be M ( Ξ + c )- M ( Ξ 0 c )=(−5±4±1)MeV.

A measurement of the tau lifetime

The tau lepton lifetime is measured using four different methods with the DELPHI detector. Three measurements using one prong decays are combined, accounting for correlations, resulting in ττ=298 ±7 (stat.)±4 (syst.) fs while the decay length distribution of three prong decays gives ππ=298±13 (stat)±(syst.) fs. The combined result is ττ=298±7 fs. The ratio of the Fermi coupling constant from tau decay relative to that from muon decay is found to be 0.985±0.013, compatible with lepton universality.

Determination of B(Ds+) via observation of Ds+l+1/2

Using the CLEO detector at the Cornell Electron Storage Ring (CESR), we have determined the ratio {Gamma}({ital D}{sub {ital s}}{sup +}{r arrow}{phi}{ital l}{sup +}{nu})/{Gamma}({ital D}{sub {ital s}}{sup +} {r arrow}{phi}{pi}{sup +})=0.49{plus minus}0.10{sub {minus}0.14}{sup +0.10}. We use this measurement to derive {ital B}({ital D}{sub {ital s}}{sup +}{r arrow}{phi}{pi}{sup +}).

Measurements of the decays tau(-) -> h(-)h(+)h(-)nu(tau) and tau(-) -> h(-)h(+)h(-)pi(0)nu(tau)

We use a data sample of 2.8 × 10 6 produced τ-pair events, obtained with the CLEO II detector, to measure B(τ - Ⅵh - h + h - (π 0 )ν τ ), where h refers to either a charged π or K. These branching fractions are measured with samples of lepton-tagged and 3 vs 3 events. We find B(τ - Ⅵh - h + h - ν τ )=0.0951±0.0007±0.0020 and B(τ - Ⅵh - h + h - π 0 ν τ )=0.0423±0.0006±0.0022. We also measure B(τ - Ⅵωh - ν τ )=0.0195±0.0007±0.0011.