D. Besson

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.

Study of the decay BX

We have measured the inclusive branching ratio for B..-->..psiX to be (1.09 +- 0.16 +- 0.21)%, and the exclusive branching ratios for B/sup -/..-->..psiK/sup -/ and B-bar /sup 0/..-->..psiK-bar /sup *//sup 0/ to be (0.09 +- 0.05)% and (0.41 +- 0.18)%, respectively. The mass difference between neutral and charged B mesons is 1.1 +- 2.1 MeV, while the difference between the mass of UPSILON(4S) and twice the mean B-meson mass is 18.5 +- 3.0 MeV. The psi momentum distribution implies a substantial two-body decay (in agreement with direct measurements), but also some combination of B..-->..psiX with M/sub X/>1.5 GeV, and B..-->..psiX.

Measurement of γγ widths of charmonium states

Abstract Using the CLEO detector at the Cornell Electron Storage Ring, we have searched for two-photon production of charmonium in four-track final states. We have measured Γ γγ ( η c )=5.9 +2.1 −1.8 ±1.9 keV, and we have obtained 95% CL upper limits of Γ γγ ( X c 0 ) Γ γγ ( X c 2 )

First observation of inclusive ψ production in ψ decays

The branching ratio for inclusive ψ production in ψ(1S) decays is measured to be (0.11 ± 0.04 ± 0.02)%.

Measurement of Ds decay modes

Abstract Using the CLEO detector, we have measured the branching ratios for the exclusive decays of the D s + meson into K ∗0 K + , K 0 K + , and K ∗+ K 0 relative to the decay D s + →φπ + to be close to unity. We have also measured the mass diference between the D s + and D + meson to be 98.5±1.5 MeV/ c 2 .

Measurement of the D0, D+ and Ds+ meson lifetimes at √s = 10.58 GeV

Abstract We have measured the lifetimes of the D0, D+ and Ds+ mesons with data from the CLEO detector. We find τD0 = (5.0 ± 0.7 ± 0.4) × 10−13s, τD+ = (11.4 ± 1.6 ± 0.7) × 10−13s and τDs+ = (4.7 ± 2.2 ± 0.5) × 10−13s, giving lifetime ratios τD+/τD0 = 2.3 ± 0.5 and τDs+/τD0 = 0.9 ± 0.5.

Observation of the decay BFX

We present evidence for inclusive F-italic-meson production in B-italic-meson decay. The product branching fraction B-italic(B-italic..-->..F-italicX-italic)B-italic(F-italic/sup +/..-->..phi..pi../sup +/) is measured to be 0.0038 +- 0.010. The F-italic momentum spectrum indicates the presence of a large component of two-body final states in the decay B-italic..-->..F-italicX-italic.