One-loop corrections to the processes e^+e^- to γ, Z to J/psi~η_c and e^+e^- to Z to J/psi~J/psi

The cross section values of $J/\psi\ \eta_c$ and $J/\psi\ J/\psi$ production in $e^+e^-$ annihilation are estimated within one-loop approximation near $Z$ pole, as well as at higher energies. Both intermediate bosons, $\gamma$ and $Z$, are taken into account. It is shown that at $Z$ mass the NLO contribution increases the cross-section values by 3.5 times.