Guy Wilkinson

Abstract:

Using e+e- collision data taken with the CLEO-c detector at the Cornell Electron Storage Ring, we have investigated the direct photon spectrum in the decay ψ(2S)→γgg. We determine the ratio of the inclusive direct photon decay rate to that of the dominant three-gluon decay rate ψ(2S)→ggg (Rγ≡⌈Γgg(γgg)/⌈(ggg)) to be Rγ(zγ>0.4)=0.070±0.002±0.019±0.011, with zγ defined as the scaled photon energy relative to the beam energy. The errors shown are statistical, systematic, and that due to the uncertainty in the input branching fractions used to extract the ratio, respectively. © 2009 The American Physical Society.

Abstract:

Using the CLEO-c detector at the Cornell Electron Storage Ring, we have measured inclusive and exclusive cross sections for the production of D+, D0 and Ds+ mesons in e+e- annihilations at 13 center-of-mass energies between 3.97 and 4.26 GeV. Exclusive cross sections are presented for final states consisting of two charm mesons (DD̄, D*D̄, D*D̄*, Ds+Ds-, Ds*+Ds-, and Ds*+Ds*-) and for processes in which the charm-meson pair is accompanied by a pion. No enhancement in any final state is observed at the energy of the Y(4260). © 2009 The American Physical Society.

Abstract:

Using e+e-→Ds-Ds*+ and Ds*-Ds+ interactions at 4170 MeV collected with the CLEO-c detector, we investigate the semileptonic decays Ds+→f0(980)e+ν and Ds+→e+ν. By examining the decay rates as functions of the four-momentum transfer squared q2, we measure the ratio [dBdq2(Ds+→f0(980)e+ν)B(f0→π+π-)]/[dBdq2(Ds+→e+ν) B(→K+K-)] at q2 of zero to be (42±11)%. This ratio has been predicted to equal the rate ratio [B(Bs→J/ψf0)B(f0→π+π-)]/ [B(Bs→J/ψ)B(→K+K-)], thus indicating that the CP eigenstate J/ψf0 could be useful for measuring CP violation via Bs mixing. Assuming a simple pole model for the form factor |f+(q2)| in the f0e+ν decay, we find a pole mass of (1.7-0.7+4.5±0.2)GeV. We also determine the f0 mass and width as (977-9+11±1) and (91-22+30±3)MeV, respectively. In addition, we present updated results for B(Ds+→f0(980)e+ν) B(f0→π+π-)=(0.20±0.03±0.01)% and B(Ds+→e+ν)=(2. 36±0.23±0.13)%. Assuming that the f0 wave function is a combination of strange and nonstrange quark-antiquark components, we use our measurement for B(Ds+→f0(980)e+ν) to extract a value of the mixing angle that we find consistent with s̄s dominance, adding to the mystery as to why the f0 decays predominantly to two pions rather than two kaons. © 2009 The American Physical Society.

Abstract:

We measure the absolute branching fractions of Ds semileptonic decays where the hadron in the final state is one of φ, η, η′, KS0, K 0, and f0, using 2.8×105 e+e-→DsDs decays collected in the CLEO-c detector at a center-of-mass energy close to 4170 MeV. We obtain B(Ds+→e+νe)=(2.29±0.37±0.11)%, B(Ds+→ηe+νe)= (2.48±0.29±0.13)%, B(Ds+→η′e+νe)=(0.91±0. 33±0.05)%, where the first uncertainties are statistical and the second are systematic. We also obtain B(Ds+→K0e+νe)=(0.37±0.10±0. 02)%, and B(Ds+→K0e+νe)=(0.18±0.07±0.01)%, which are the first measurements of Cabibbo suppressed exclusive Ds semileptonic decays, and, B(Ds+→f0e+νe)×B(f0→π+π-)=(0.13±0.04±0.01) %. This is the first absolute product branching fraction determination for a semileptonic decay including a scalar meson in the final state. © 2009 The American Physical Society.