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arXiv · 1705.06853

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

BESIII Collaboration·M. Ablikim·M. N. Achasov·S. Ahmed·M. Albrecht·M. Alekseev·A. Amoroso·F. F. An·Q. An·J. Z. Bai·Y. Bai·O. Bakina·R. Baldini Ferroli·Y. Ban·D. W. Bennett·J. V. Bennett·N. Berger·M. Bertani·D. Bettoni·J. M. Bian·F. Bianchi·E. Boger·I. Boyko·R. A. Briere·H. Cai·X. Cai·O. Cakir·A. Calcaterra·G. F. Cao·S. A. Cetin·J. Chai·J. F. Chang·G. Chelkov·G. Chen·H. S. Chen·J. C. Chen·M. L. Chen·S. J. Chen·X. R. Chen·Y. B. Chen·X. K. Chu·G. Cibinetto·H. L. Dai·J. P. Dai·A. Dbeyssi·D. Dedovich·Z. Y. Deng·A. Denig·I. Denysenko·M. Destefanis·F. De Mori·Y. Ding·C. Dong·J. Dong·L. Y. Dong·M. Y. Dong·O. Dorjkhaidav·Z. L. Dou·S. X. Du·P. F. Duan·J. Fang·S. S. Fang·X. Fang·Y. Fang·R. Farinelli·L. Fava·S. Fegan·F. Feldbauer·G. Felici·C. Q. Feng·E. Fioravanti·M. Fritsch·C. D. Fu·Q. Gao·X. L. Gao·Y. Gao·Y. G. Gao·Z. Gao·B. Garillon·I. Garzia·K. Goetzen·L. Gong·W. X. Gong·W. Gradl·M. Greco·M. H. Gu·S. Gu·Y. T. Gu·A. Q. Guo·L. B. Guo·R. P. Guo·Y. P. Guo·Z. Haddadi·S. Han·X. Q. Hao·F. A. Harris·K. L. He·X. Q. He·F. H. Heinsius·T. Held
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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 ($\le3.0\sigma$), 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 $\sigma_{\mathrm{ peak}}(e^+e^-\to\gamma\eta_c(1S)) = 2.11 \pm 0.49 (\mathrm{stat.}) \pm 0.36 (\mathrm{syst.})$~pb with a statistical significance of 4.2$\sigma$.

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BESIII Collaboration, M. Ablikim, M. N. Achasov, S. Ahmed, M. Albrecht, M. Alekseev, A. Amoroso, F. F. An, Q. An, J. Z. Bai, Y. Bai, O. Bakina, R. Baldini Ferroli, Y. Ban, D. W. Bennett, J. V. Bennett, N. Berger, M. Bertani, D. Bettoni, J. M. Bian, F. Bianchi, E. Boger, I. Boyko, R. A. Briere, H. Cai, X. Cai, O. Cakir, A. Calcaterra, G. F. Cao, S. A. Cetin, J. Chai, J. F. Chang, G. Chelkov, G. Chen, H. S. Chen, J. C. Chen, M. L. Chen, S. J. Chen, X. R. Chen, Y. B. Chen, X. K. Chu, G. Cibinetto, H. L. Dai, J. P. Dai, A. Dbeyssi, D. Dedovich, Z. Y. Deng, A. Denig, I. Denysenko, M. Destefanis, F. De Mori, Y. Ding, C. Dong, J. Dong, L. Y. Dong, M. Y. Dong, O. Dorjkhaidav, Z. L. Dou, S. X. Du, P. F. Duan, J. Fang, S. S. Fang, X. Fang, Y. Fang, R. Farinelli, L. Fava, S. Fegan, F. Feldbauer, G. Felici, C. Q. Feng, E. Fioravanti, M. Fritsch, C. D. Fu, Q. Gao, X. L. Gao, Y. Gao, Y. G. Gao, Z. Gao, B. Garillon, I. Garzia, K. Goetzen, L. Gong, W. X. Gong, W. Gradl, M. Greco, M. H. Gu, S. Gu, Y. T. Gu, A. Q. Guo, L. B. Guo, R. P. Guo, Y. P. Guo, Z. Haddadi, S. Han, X. Q. Hao, F. A. Harris, K. L. He, X. Q. He, F. H. Heinsius, T. Held. 2017-05-19. Evidence for $e^{+}e^{-} \to \gamma\eta_c(1S)$ at center-of-mass energies between 4.01 and 4.60 GeV. https://doi.org/10.1103/physrevd.96.051101

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