Evidence for $e^{+}{e}^{-}\to \gamma {\eta }_c(1S)$ at center-of-mass energies between 4.01 and 4.60 GeV

Abstract

We present first evidence for the process $e^{+}{e}^{-}\to \gamma {\eta }_c(1S)$ at six center-of-mass energies between 4.01 and 4.60~GeV using data collected by the BESIII experiment operating at BEPCII. These data sets correspond to a total integrated luminosity of 4.6~fb${}^{-1}$. We measure the Born cross section at each energy using a combination of twelve ${\eta }_c(1S)$ decay channels. Because the significance of the signal is marginal at each energy ($\le 3.0\sigma$), 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 ${\sigma }_{\mathrm{peak}}(e^{+}{e}^{-}\to \gamma {\eta }_c(1S))=2.11\pm 0.49(stat.)\pm 0.36(syst.)$~pb with a statistical significance of 4.2$\sigma$.

8 pages, 2 figures

References in corpus (2)

• Exotic and excited-state radiative transitions in charmonium from lattice QCD
• Evidence for η_{c}(2S) in ψ(3686) \to γK_{S}^{0}K^{\pm}π^{\mp}π^{+}π^{-}

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