Observation of $e^{+}{e}^{-}\to \eta \psi (2S)$ at center-of-mass energies from 4.236 to 4.600 GeV

Abstract

Using a total of $5.25{\mathrm{fb}}^{-1}$ of $e^{+}{e}^{-}$ collision data with center-of-mass energies from 4.236 to 4.600 GeV, we report the first observation of the process $e^{+}{e}^{-}\to \eta \psi (2S)$ with a statistical significance of $5\sigma$. The data sets were collected by the BESIII detector operating at the BEPCII storage ring. We measure the yield of events integrated over center-of-mass energies and also present the energy dependence of the measured cross section.