One-loop corrections to the processes $e^{+}{e}^{-}\to \gamma ,Z\to J\mathrm{/}\psi {\eta }_c$ and $e^{+}{e}^{-}\to Z\to J\mathrm{/}\psi J\mathrm{/}\psi$

The cross section values of $J\mathrm{/}\psi {\eta }_c$ and $J\mathrm{/}\psi J\mathrm{/}\psi$ 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.