Exclusive charmonium +γ and bottomonium +γ production in a potential scheme

In recent years the new experimental results from Belle, BaBar, CLEO, CDF and D0 collaboration have induced renewed theoretical interest in understanding the mass spectrum, decay and production mechanisms of charmonium and bottomonium states. The charmonium production has been studied in various processes, such as in hadron-hadron collision, electron-proton collision, fixed target experiments, B meson decays, as well as Z0 decays. The BaBar and Belle have been studied the double charmonium production in e+e- annihilation is particularly interesting in testing the quarkonium production mechanisms of the color-singlet model and the color-octet model in the nonrelativistic QCD (NRQCD) factorization approach