Cross Section Measurement Of E~+e~-→ηJ/ψand Searches For E~+e~-→π~0J/ψ At BESⅢ

The hadron transition process has been a powerful tool for studying charmonium.In order to study a particle of unknown nature,it is often necessary to measure this particle by radiating η,π⁰or two π mesons（π⁺π^-/π⁰π⁰）decay to the low energy char-monium.Belle,BESIII and CLEO-c have measured the production cross sections of e⁺e^-→ηJ/ψabove the open charm region.However,Belle and CLEO-c results suffer from large statistical uncertainties,and BESIII reported on a more accurate result,but at 9 center-of-mass（c.m.）energy points only.Experimental studies with large data samples and a broad energy region may shed light to insight and reveal the nature of Y（4230）.We report the measurements of production Born cross sections of e⁺e^-→ηJ/ψat 27 c.m.energy between 3.81 and 4.60GeV by using the data samples with a total integrated luminosity of 13.13fb^-1 collected with the BEIII detector operating at the BEPCII storage ring,where η is reconstructed with its two dominant decay modes η→YY and η→π⁺π^-π⁰,and J/ψis reconstructed with lepton pairs l⁺l^-（l=e,μ）.Two structures,namely ψ（4040）and Y（4230）,are observed on the mea-sured center-of-mass energy dependent cross sections.The maximum likelihood fits with a coherent sum function of two Breit-Wigner functions are carried out,yields mass and width of Y（4230）be 4218.7±3.5±3.0MeV和 68.6±5.5±3.8MeV.We also perform the searching for the decay e⁺e^-→π⁰J/ψ in the same c.m.energy region,no evidence for a signal is observed.