Observation of $e^{+}e^{-} to eta^{prime} J/psi$ at center-of-mass energies between 4.189 and 4.600 GeV

The process $e^{+}e^{-}to eta^{prime} J/psi$ is observed for the first time with a statistical significance of $8.6sigma$ at center-of-mass energy $sqrt{s} = 4.226$ GeV and $7.3sigma$ at $sqrt{s} = 4.258$ GeV using data samples collected with the BESIII detector. The Born cross sections are measured to be $(3.7 pm 0.7 pm 0.3)$ and $(3.9 pm 0.8 pm 0.3)$ pb at $sqrt{s} = 4.226$ and $4.258$ GeV, respectively, where the first errors are statistical and the second systematic. Upper limits at the 90% confidence level of the Born cross sections are also reported at other 12 energy points.