Guy Wilkinson

Abstract:

Using Υ(2S) and Υ(3S) data collected with the CLEO III detector we have searched for decays of χbJ to final states with open charm. We fully reconstruct D0 mesons with pD0>2.5GeV/c in three decay modes (K-π+, K-π+π0, and K-π-π+π+) in coincidence with radiative transition photons that tag the production of one of the χbJ(nP) states. Significant signals are obtained for the two J=1 states. Recent nonrelativistic QCD (NRQCD) calculations of χbJ(nP)→cc̄X depend on one nonperturbative parameter per χbJ triplet. The extrapolation from the observed D0X rate over a limited momentum range to a full cc̄X rate also depends on these same parameters. Using our data to fit for these parameters, we extract results which agree well with NRQCD predictions, confirming the expectation that charm production is largest for the J=1 states. In particular, for J=1, our results are consistent with cc̄g accounting for about one-quarter of all hadronic decays. © 2008 The American Physical Society.

Abstract:

Analyzing Y(nS) decays acquired with the CLEO detector operating at the CESR e+e- collider, we measure for the first time the product branching fractions B[Y(nS)→YX bJ((n-1)P)]B[X bJ(n-1)P)→Xi] for n=2 and 3, where Xi denotes, for each i, one of the 14 exclusive light-hadron final states for which we observe significant signals in both X bJ(1P) and X bJ(2P) decays. We also determine upper limits for the electric dipole (E1) transitions Y(3S)→YX bJ(1P). © 2008 The American Physical Society.

Abstract:

We report the first observation of Υ(2S)→ηΥ(1S), with a branching fraction B=(2.1-0.6+0.7(stat)±0.3(syst))×10-4 and a statistical significance 5.3σ. Data were acquired with the CLEO III detector at the CESR e+e- symmetric collider. This is the first process observed involving a b-quark spin flip. For related transitions, 90% confidence limits in units of 10-4 are B(Υ(2S)→π0Υ(1S))<1.8, B(Υ(3S)→ηΥ(1S))<1.8, B(Υ(3S)→π0Υ(1S)) <0.7, and B(Υ(3S)→π0Υ(2S))<5.1. © 2008 The American Physical Society.

Abstract:

We measure the mass of the eta;{'} meson using psi(2S)-->pi;{+}pi;{-}J/psi, J/psi-->gammaeta;{'} events acquired with the CLEO-c detector operating at the CESR e;{+}e;{-} collider. Using three decay modes, eta;{'}-->rho;{0}gamma, eta;{'}-->pi;{+}pi;{-}eta with eta-->gammagamma, and eta;{'}-->pi;{+}pi;{-}eta with eta-->pi;{+}pi;{-}pi;{0}, we find M_{eta;{'}}=957.793+/-0.054+/-0.036 MeV, in which the uncertainties are statistical and systematic, respectively. This result is consistent with but substantially more precise than the current world average.

Abstract:

A precision measurement of the mass of the hc(P11) state of charmonium has been made using a sample of 24.5×106 ψ(2S) events produced in e+e- annihilation at the Cornell Electron Storage Ring (CESR). The reaction used was ψ(2S)→π0hc, π0→γγ, hc→γηc, and the reaction products were detected in the CLEO-c detector. Data have been analyzed both for the inclusive reaction and for the exclusive reactions in which ηc decays are reconstructed in 15 hadronic decay channels. Consistent results are obtained in the two analyses. The averaged results of the present measurements are M(hc)=3525.28±0.19(stat.)±0.12(syst.)MeV, and B(ψ(2S)→π0hc)×B(hc→γηc)=(4.19±0. 32±0.45)×10-4. Using the PJ3 centroid mass, ΔMhf(1P) M(χcJ) -M(hc)=+0.02±0.19±0.13MeV. © 2008 The American Physical Society.