Partial wave analysis of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>J</mml:mi><mml:mo>/</mml:mo><mml:mi>ψ</mml:mi><mml:mo stretchy="false">→</mml:mo><mml:mi>γ</mml:mi><mml:msup><mml:mi>η</mml:mi><mml:mo>′</mml:mo></mml:msup><mml:msup><mml:mi>η</mml:mi><mml:mo>′</mml:mo></mml:msup></mml:math>
M. Ablikim, М. Н. Ачасов, P. Adlarson, S. Ahmed, M. Albrecht, R. Aliberti, A. Amoroso, M. R. An, Q. An, X. H. Bai, Y. Bai, O. Bakina, R. Baldini Ferroli, I. Balossino, Y. Ban, K. Begzsuren, N. Berger, M. Bertani, D. Bettoni, F. Bianchi, J. Bloms, A. Bortone, I. Boyko, R. A. Briere, H. Cai, X. Z. Cai, A. Calcaterra, G. F. Cao, N. Cao, S. A. Çetin, J. F. Chang, W. L. Chang, G. Chelkov, Daiwei Chen, G. Chen, H. S. Chen, M. L. Chen, Shiwei Chen, X. R. Chen, Yongxu Chen, Zhifu Chen, W. S. Cheng, G. Cibinetto, F. Cossio, X. F. Cui, H. L. Dai, J. P. Dai, X. Dai, A. Dbeyssi, R. E. de Boer, 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, X. Dong, S. X. Du, P. Egorov, Y. L. Fan, J. Fang, S. S. Fang, Y. Fang, R. Farinelli, L. Fava, F. Feldbauer, G. Felici, C. Q. Feng, J. H. Feng, M. Fritsch, C. D. Fu, Y. Gao, Y. Gao, Y. Gao, I. Garzia, P. T. Ge, C. Geng, E. Gersabeck, A. Gilman, K. Goetzen, L. Gong, W. X. Gong, W. Gradl, M. Greco, L. M. Gu, M. H. Gu, C. Y. Guan, A. Q. Guo, A. Q. Guo, L. B. Guo, R. P. Guo, Y. P. Guo, A. Guskov, T. T. Han, W. Y. Han
Abstract
Using a sample of $(10.09\ifmmode\pm\else\textpm\fi{}0.04)\ifmmode\times\else\texttimes\fi{}{10}^{9}$ $J/\ensuremath{\psi}$ events collected with the BESIII detector, a partial wave analysis of $J/\ensuremath{\psi}\ensuremath{\rightarrow}\ensuremath{\gamma}{\ensuremath{\eta}}^{\ensuremath{'}}{\ensuremath{\eta}}^{\ensuremath{'}}$ is performed. The masses and widths of the observed resonances and their branching fractions are reported. The main contribution is from $J/\ensuremath{\psi}\ensuremath{\rightarrow}\ensuremath{\gamma}{f}_{0}(2020)$ with ${f}_{0}(2020)\ensuremath{\rightarrow}{\ensuremath{\eta}}^{\ensuremath{'}}{\ensuremath{\eta}}^{\ensuremath{'}}$, which is found with a significance of greater than $25\ensuremath{\sigma}$. The product branching fraction $\mathcal{B}(J/\ensuremath{\psi}\ensuremath{\rightarrow}\ensuremath{\gamma}{f}_{0}(2020))\ifmmode\cdot\else\textperiodcentered\fi{}\mathcal{B}({f}_{0}(2020)\ensuremath{\rightarrow}{\ensuremath{\eta}}^{\ensuremath{'}}{\ensuremath{\eta}}^{\ensuremath{'}})$ is measured to be $(2.63\ifmmode\pm\else\textpm\fi{}0.06(\mathrm{stat}.{)}_{\ensuremath{-}0.46}^{+0.31}(\mathrm{syst}.))\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$.