Meson-Photon Transition Form Factors in the Charmonium Energy Range

Abstract

The study of electron-positron collisions at center-of-mass energies corresponding to charmonium production has reached new levels of sensitivity thanks to experiments by the BES and CLEO Collaborations. Final states $γP$, where $P$ is a pseudoscalar meson such as $π^0$, $η$, and $η'$ can arise either from charmonium decays or in the continuum through a virtual photon: $e^+ e^- \to γ^* \to γP$. Estimates of this latter process are given at center-of-mass (c.m.) energies corresponding to the $J/ψ(1S)$, $ψ(2S)$, and $ψ(3770)$ resonances.