Related papers: Prospects for detecting an $\eta_c'$ in two photon…
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…
The two-photon width $\Gamma_{\gamma\gamma}$ of the $\eta_c$ meson has been measured with the L3 detector at LEP. The $\eta_c$ is studied in the decay modes $\pi^+\pi^-\pi^+\pi^-$, $\pi^+\pi^-$K$^+$K$^-$, K$_s^0$K$^\pm\pi^\mp$,…
eta_c(2980) production in gamma-gamma interactions has been detected via its decays into K0_s K+/- pi-/+, K+ K- K+ K- and K+ K- pi+ pi- in the data taken with the DELPHI detector at LEP1 and LEP2 energies. The two-photon radiative width…
The relation between the ratio Gamma_{ee}(psi')/Gamma_{ee}(J/psi) and Gamma_{2gamma}(eta_{c}')/Gamma_{2gamma}(eta_{c}), expressed in terms of the configuration mixing amplitudes induced by the contact spin-spin interaction of quarks in the…
A search for the production of the $\eta'_c$ meson, the first radial excitation of the ground state of charmonium $\eta_c$(2980), in the photon-photon fusion reaction at LEP has been performed using the data collected by the DELPHI detector…
We analyze 13.8 \rm fb^{-1} of the integrated e^+e^- luminosity collected at 10.6 GeV center-of-mass energy with the CLEO II and CLEO II.V detectors to study exclusive two-photon production of hadrons with masses below 1.7{\rm \ GeV/c^2}…
We report on the observation of the eta_{c}^{prime}(2^{1}S_{0}), the radial excitation of eta_{c}(1^{1}S_{0}) ground state of charmonium, in the two-photon fusion reaction gamma gamma rightarrow eta_{c}^{prime} rightarrow…
We analyzed 13.8 fb^{-1} of the integrated e+e- luminosity collected at 10.6 GeV center-of-mass energy with the CLEO II and II.V detectors to study exclusive two-photon production of single hadronic resonances. We searched for hadrons…
We study the processes $\gamma \gamma \to K^+ K^- \eta$ and $\gamma \gamma \to K^+ K^- \pi^0$ using a data sample of 519 $fb^{-1}$ recorded with the BaBar detector operating at the SLAC PEP-II asymmetric-energy $e^+ e^-$ collider at…
Electromagnetic interactions of the ground and first radial excited states of $\eta$ and $\eta'$ mesons in the framework of the extended $U(3)\times U(3)$ NJL model are considered. The radial excitations are described with the help of…
One of the main goals of future electron-ion colliders is to improve our understanding of the structure of hadrons. In this letter, we study the exclusive $\eta_c$ production by $\gamma^{*} \gamma$ interactions in $eA$ collisions and…
In this paper we analyzed the exclusive photoproduction of $\eta_{c}\gamma$ pairs in the Color Glass Condensate framework. We found that the cross-section of this process is sensitive only to the forward dipole scattering amplitude, and…
Data collected by the KLOE experiment in years 2001/2002 for a total integrated luminosity of 410 pb$^{-1}$, corresponding to 17 million of produced $\eta$'s from the $\Phi \to \eta\gamma$ radiative decay, have been analyzed to look for the…
We discuss the measured partial width of the pseudoscalar charmonium state eta_c into two photons. Predictions from potential models are examined and compared with experimental values. Including radiative corrections, it is found that…
We report the first measurement of the differential cross section for the process gamma gamma --> eta eta in the kinematic range above the eta eta threshold, 1.096 GeV < W < 3.8 GeV over nearly the entire solid angle range, |cos theta*| <=…
A search for the pseudoscalar meson eta_b was performed at LEP~II energies with an integrated luminosity of 700pb^-1. The search, done for the decay modes into 4 and 6 charged particles yielded 0 and 1 candidates, respectively. Upper limits…
We evaluate the two-photon width of the pseudoscalar charmonia, Gamma(eta_c -> gamma gamma) and Gamma(eta'_c -> gamma gamma), within a Heavy-Quark Spin-Symmetry setting and show that whereas the former agrees with experiment, the latter is…
We study the processes $\gamma \gamma \to \eta_c \to \eta' K^+ K^-$, $\eta' \pi^+ \pi^-$, and $\eta \pi^+ \pi^-$ using a data sample of 519 $fb^{-1}$ recorded with the BaBar detector operating at the SLAC PEP-II asymmetric-energy $e^+e^-$…
A search for the pseudoscalar meson eta_b is performed in two-photon interactions at LEP~2 with an integrated luminosity of 699 pb^-1 collected at e+e- centre-of-mass energies from 181 GeV to 209 GeV. One candidate event is found in the…
Using 13.4 $fb^{-1}$ of data collected with the CLEO detector at the Cornell Electron Storage Ring, we have observed 300 events for the two-photon production of ground-state pseudo-scalar charmonium in the decay $\eta_c$ -> $K_S K^{\mp}…