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We report on the observation of the eta_c^ (2 ^1S_0), the radial excitation of eta_c (1 ^1S_0) ground state of charmonium, in the two-photon fusion reaction gamma gamma to eta_c^ to K_S^0 K^{pm} pi^{mp} in 13.4 fb^{-1} of CLEO II/II.V data and 9.2 fb^{-1} of CLEO III data. The data have been analyzed to extract the eta_c^ resonance parameters.
We have observed exclusive gammagamma production in proton-antiproton collisions at sqrt{s}=1.96 TeV, using data from 1.11 pm 0.07 fb^{-1} integrated luminosity taken by the Run II Collider Detector at Fermilab. We selected events with two electromag
We present a study of the inclusive photon spectra from 5.9 million J/psi decays collected with the KEDR detector at the VEPP-4M e+e- collider. We measure the branching fraction of radiative decay J/psi to eta_c gamma, eta_c width and mass. Our preli
We present a study of the inclusive photon spectrum from 6.3 million J/psi decays collected with the KEDR detector at the VEPP-4M e+e- collider. We measure the branching fraction of the radiative decay J/psi -> eta_c gamma, eta_c width and mass. Taki
The production of two high-p_T jets in the interactions of quasi-real photons in e+e- collisions at sqrt{s_ee} from 189 GeV to 209 GeV is studied with data corresponding to an integrated e+e- luminosity of 550 pb^{-1}. The jets reconstructed by the k
The mass and width of the lowest lying S-wave spin singlet charmonium state, the eta_c, are measured using a data sample of 1.06x10^8 psi decays collected with the BESIII detector at the BEPCII storage ring. We use a model that incorporates interfere