Evidence for e+e−→γηc(1S) at center-of-mass energies between 4.01 and 4.60 GeV

摘要

We present first evidence for the process e+e− → gamma eta_c(1S) at six center-of-mass energies between 4.01 and 4.60 GeV using data collected by the BESIII experiment operating at BEPCII. We measure the Born cross section at each energy using a combination of twelve eta_c(1S) decay channels. We also combine all six energies under various assumptions for the energy-dependence of the cross section. If the process is assumed to proceed via the Y(4260), we measure a peak Born cross section σ_peak(e+e− → γ eta_c(1S)) = 2.11 pm 0.49(stat.) pm 0.36(cyst.) pb with a statistical significance of 4.2σ.