Higher-order corrections to exclusive production of charmonia at B   factories
  As a test of the color-singlet mechanism of the nonrelativistic QCD (NRQCD) factorization approach, we consider the exclusive two-quarkonium productions in electron-positron annihilation e+ e- -> eta_c + gamma and e+ e- -> J/psi + J/psi at B factories. The cross sections are computed to the next-to-leading order in alpha_s and are resummed to all orders in half the relative velocity v of the charm quark in each meson rest frame. The available theoretical prediction of the cross section for e+ e- -> J/psi + eta_c at the same level of theoretical accuracies is consistent with the available experimental data. Those for e+ e- -> eta_c + gamma and e+ e- -> J/psi + J/psi that are computed new in this work can be tested against the data from future super B factories. 
Ying Fan, Jungil Lee, Chaehyun Yu
hep-ph hep-ex