Guy Wilkinson

Abstract:

Using a sample of 2.59×107 ψ(2S) decays collected by the CLEO-c detector, we present results of a study of χc0 and χc2 decays into two-meson final states. We present the world's most precise measurements of the χcJ,(J=0,2)→π+π-, π0π0, K+K-, KS0KS0, ηη, and η′η′ branching fractions, and a search for χc decays into ηη′. These results shed light on the mechanism of charmonium decays into pseudoscalar mesons. © 2009 The American Physical Society.

Abstract:

We have studied the leptonic decay Ds+→τ+ντ, via the decay channel τ+→e+νeν̄τ, using a sample of tagged Ds+ decays collected near the Ds*±Ds peak production energy in e+e- collisions with the CLEO-c detector. We obtain B(Ds+→τ+ντ)=( 5.30±0.47±0.22)% and determine the decay constant fDs=(252.5±11.1± 5.2)MeV, where the first uncertainties are statistical and the second are systematic. © 2009 The American Physical Society.

Abstract:

We examine e+e-→Ds-Ds*+ and Ds*-Ds+ interactions at 4170 MeV using the CLEO-c detector in order to measure the decay constant fDs+ with good precision. Previously our measurements were substantially higher than the most precise lattice based QCD calculation of (241± 3)MeV. Here we use the Ds+→+ν channel, where the + designates either a μ+ or a τ+, when the τ+→π+ν̄. Analyzing both modes independently, we determine B(Ds+→μ+ν)=( 0.565±0.045±0.017)%, and B(Ds+→τ+ν)=(6.42±0.81± 0.18)%. We also analyze them simultaneously to find an effective value of Beff(Ds+→μ+ν)=(0.591± 0.037±0.018)% and fDs+=( 263.3±8.2±3.9)MeV. Combining with the CLEO-c value determined independently using Ds+→τ+ν, τ+→e+νν̄ decays, we extract fDs+=( 259.5±6.6±3.1)MeV. Combining with our previous determination of B(D+→μ+ν), we extract the ratio fDs+/fD+=1.26±0.06±0.02. No evidence is found for a CP asymmetry between Γ(Ds+→μ+ν) and Γ(Ds-→μ-ν); specifically the fractional difference in rates is measured to be (4.8±6.1)%. Finally, we find B(Ds+→e+ν)<1.2×10-4 at 90% confidence level. © 2009 The American Physical Society.

Abstract:

Using ψ(3770)→DD̄ events collected with the CLEO-c detector at the Cornell e+e- storage ring, tagged by fully reconstructing one D meson in a hadronic decay mode, we measure absolute branching fractions and differential decay rates for D0→π-e+νe, D+→π0e+νe, D0→K-e+νe, and D+→K̄0e+νe. The measured decay rates are used to study semileptonic form factors governing these transitions and to test unquenched Lattice QCD (LQCD) calculations. We average our results with previously published CLEO-c measurements of the same quantities using a neutrino reconstruction technique. Combining LQCD calculations of form factor absolute normalizations f+(0) and measurements of f+π(0)|Vcd| and f+K(0)|Vcs|, we find |Vcd|=0.222(8)(3)(23) and |Vcs|=1.018(10)(8)(106), where the uncertainties are statistical, experimental systematic, and from LQCD, respectively. © 2009 The American Physical Society.

Abstract:

Measurements are presented of R b, the ratio of the cross-section to the cross-section in e+e- collisions, and the forward-backward asymmetry A FBb at twelve energy points in the range sqrt{s}=130-207 GeV. These results are found to be consistent with the Standard Model expectations. The measurements are used to set limits on new physics scenarios involving contact interactions. © 2009 Springer-Verlag / Società Italiana di Fisica.