Guy Wilkinson

Abstract:

Using 24×106 ψ′≡ψ(2S) decays in CLEO-c, we have searched for higher multipole admixtures in electric-dipole-dominated radiative transitions in charmonia. We find good agreement between our data and theoretical predictions for magnetic quadrupole (M2) amplitudes in the transitions ψ′→γχc1,c2 and χc1,c2→γJ/ ψ, in striking contrast to some previous measurements. Let b2J and a2J denote the normalized M2 amplitudes in the respective aforementioned decays, where the superscript J refers to the angular momentum of the χcJ. By performing unbinned maximum likelihood fits to full five-parameter angular distributions, we found the following values of M2 admixtures for Jχ=1: a2J=1=(-6.26±0.63±0.24)×10-2 and b2J=1=(2.76±0. 73±0.23)×10-2, which agree well with theoretical expectations for a vanishing anomalous magnetic moment of the charm quark. For Jχ=2, if we fix the electric octupole (E3) amplitudes to zero as theory predicts for transitions between charmonium S states and P states, we find a2J=2=(-9.3±1.6±0.3)×10-2 and b2J=2=(1.0±1. 3±0.3)×10-2. If we allow for E3 amplitudes we find, with a four-parameter fit, a2J=2=(-7.9±1.9±0.3)×10-2, b2J=2=(0.2±1.4±0.4)×10-2, a3J=2=(1.7±1.4±0.3) ×10-2, and b3J=2=(-0.8±1.2±0.2)×10-2. We determine the ratios a2J=1/a2J=2=0.67-0.13+0.19 and a2J=1/b2J=1=-2.27-0.99+0.57, where the theoretical predictions are independent of the charmed quark magnetic moment and are a2J=1/a2J=2=0.676±0.071 and a2J=1/b2J=1=-2.27±0.16. © 2009 The American Physical Society.

Abstract:

Analyzing 600pb-1 of e+e- collisions at 4170 MeV center-of-mass energy with the CLEO-c detector, we measure the branching fraction B(Ds+→τ+ν)= (5.52±0.57±0.21)% using the τ+→ρ+ν̄ decay mode. Combining with other CLEO measurements of B(Ds+→τ+ν) we determine the pseudoscalar decay constant fDs=(259.7±7.8±3.4)MeV consistent with the value obtained from our Ds+→μ+ν measurement of (257.6±10.3±4.3)MeV. Combining these measurements we find a value of fDs=(259.0±6.2±3.0)MeV, that differs from the most accurate prediction based on unquenched lattice gauge theory of (241±3)MeV by 2.4 standard deviations. We also present the first measurements of B(Ds+→K0π+π0)=(1.00±0.18±0.04)%, and B(Ds+→π+π0π0)=(0.65±0.13±0.03)%, and measure a new value for B(Ds+→ηρ+)=(8.9±0.6±0.5)%. © 2009 The American Physical Society.

Abstract:

A survey is made of selected topics in flavour physics where real progress is expected in the coming half-decade, paying particular attention to those where New Physics signals may appear. © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence.

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.