Observation of e(+)e(-)→π(0)π(0)hc and a neutral charmoniumlike structure Zc(4020)(0).


Using data collected with the BESIII detector operating at the Beijing Electron Positron Collider at center-of-mass energies of sqrt[s]=4.23, 4.26, and 4.36 GeV, we observe e(+)e(-)→π(0)π(0)hc for the first time. The Born cross sections are measured and found to be about half of those of e(+)e(-)→π(+)π(-)hc within less than 2σ. In the π(0)hc mass spectrum, a structure at 4.02  GeV/c(2) is found. It is most likely to be the neutral isospin partner of the Zc(4020)(±) observed in the process of e(+)e(-)→π(+)π(-)hc being found. A fit to the π(0)hc invariant mass spectrum, with the width of the Zc(4020)(0) fixed to that of its charged isospin partner and possible interferences with non-Zc(4020)(0) amplitudes neglected, gives a mass of (4023.9±2.2±3.8)  MeV/c(2) for the Zc(4020)(0), where the first error is statistical and the second systematic.

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@article{Ablikim2014ObservationOE, title={Observation of e(+)e(-)→π(0)π(0)hc and a neutral charmoniumlike structure Zc(4020)(0).}, author={Melike Ablikim and M . N . Achasov and X. C. Ai and Onur Albayrak and Marcus Albrecht and Divakar Justus Ambrose and Antonio Amoroso and Fengpeng An and Qi An and Jing Bai and R B F Baldini Ferroli and Yoshitsune Ban and David W. Bennett and John V. Bennett and M. B. Bertani and Diego Bettoni and Jian-min Bian and Francesca Bianchi and Elin Boger and Oleg Bondarenko and Igor Boyko and R . A . Briere and H C Cai and X . Z . Cai and Orhan Cakir and Andrea Calcaterra and Gang Cao and S. A. Çetin and J . F . Chang and G . A . Chelkov and Gui-ping Chen and Huan Chen and H . Y . Chen and Joseph Chen and M Chen and S Chen and Xu Chen and Xue Rong Chen and Y Chen and Heping Cheng and X K Chu and Y. Chu and Gianluigi Cibinetto and Dan Cronin-Hennessy and H. L. Dai and Jian Dai and D . V . Dedovich and Zhiting Deng and Achim G. Denig and I B Denysenko and Marco Destefanis and F De Mori and Yang Ding and C Dong and Jun Dong and Lin Dong and M. Dong and S. X. Du and Piaopiao Duan and J. Fan and Jinggui Fang and S Fang and Xiang Fang and Yi Fang and Luciano Fava and F . Feldbauer and G. Felici and Chao Feng and Emiliano Fioravanti and C Fu and Q X Gao and Y. Gao and I . Garzia and Klaus Goetzen and W. X. Gong and Wolfgang Gradl and Massimo Greco and Mai Gu and Yan Gu and Yue Guan and Author Guo and L. Guo and T W Guo and Yue Guo and Z. Haddadi and Annette Hafner and S. H. Han and Y. Han and Frederick A. Harris and Kan Lian He and Zhi He and Theo Held and Yee Kiat Heng and Zhonghuai Hou and Chunhong Hu and H Hu and Jin Hu and Ting Hu and Y Hu and G. M. Huang and G. 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