Measurement of $e^{+}e^{-}\rightarrow\eta J/\psi$ Cross Section from $\sqrt{s}=$ 3.808 GeV to 4.951 GeV

TL;DR

This study measures the cross section of the process $e^{+}e^{-} ightarrow ext{eta} J/ ext{psi}$ across a range of energies, revealing three resonant structures and providing precise parameters for two known states.

Contribution

First measurement of the $e^{+}e^{-} ightarrow ext{eta} J/ ext{psi}$ cross section over a broad energy range with detailed resonance analysis.

Findings

Observation of three structures in the cross section line shape.

Precise mass and width measurements for $ ext{psi}(4230)$ and $ ext{psi}(4360)$.

High statistical significance of the observed resonances.

Abstract

Using data samples with an integrated luminosity of 22.42 fb$^{-1}$ collected by the BESIII detector operating at the BEPCII storage ring, we measure the cross sections of the $e^{+}e^{-}\rightarrow\etaJ/\psi$ process at center-of-mass energies from 3.808 to 4.951 GeV. Three structures are observed in the line shape of the measured cross sections. A maximum-likelihood fit with $\psi(4040)$, two additional resonances, and a non-resonant component is performed. The mass and width of the first additional state are $(4219.7\pm2.5\pm4.5) \rm{MeV}/\rm{c}^2$ and $(80.7\pm4.4\pm1.4) \rm{MeV}$, respectively, consistent with the $\psi(4230)$. For the second state, the mass and width are $(4386\pm13\pm17) \rm{MeV}/\rm{c}^2$ and $(177\pm32\pm13) \rm{MeV}$, respectively, consistent with the $\psi(4360)$. The first uncertainties are statistical and the second ones are systematic. The statistical significance of $\psi(4040)$ is $8.0\sigma$ and those for $\psi(4230)$ and $\psi(4360)$ are more than $10.0\sigma$.