Observation of a charged charmoniumlike structure Zc(4020) and search for the Zc(3900) in e+e- → π+π-hc

M. Ablikim, M. N. Achasov, O. Albayrak, D. J. Ambrose, F. F. An, Q. An, J. Z. Bai, R. Baldini Ferroli, Y. Ban, J. Becker, J. V. Bennett, M. Bertani, J. M. Bian, E. Boger, O. Bondarenko, I. Boyko, S. Braun, R. A. Briere, V. Bytev, H. CaiX. Cai, O. Cakir, A. Calcaterra, G. F. Cao, S. A. Cetin, 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, H. P. Cheng, X. K. Chu, Y. P. Chu, D. Cronin-Hennessy, H. L. Dai, J. P. Dai, D. Dedovich, Z. Y. Deng, A. Denig, I. Denysenko, M. Destefanis, W. M. Ding, Y. Ding, L. Y. Dong, M. Y. Dong, S. X. Du, J. Fang, S. S. Fang, L. Fava, C. Q. Feng, P. Friedel, C. D. Fu, J. L. Fu, O. Fuks, Y. Gao, C. Geng, K. Goetzen, W. X. Gong, W. Gradl, M. Greco, M. H. Gu, Y. T. Gu, Y. H. Guan, A. Q. Guo, L. B. Guo, T. Guo, Y. P. Guo, Y. L. Han, F. A. Harris, K. L. He, M. He, Z. Y. He, T. Held, Y. K. Heng, Z. L. Hou, C. Hu, H. M. Hu, J. F. Hu, T. Hu, G. M. Huang, G. S. Huang, J. S. Huang, L. Huang, X. T. Huang, Y. Huang, T. Hussain, C. S. Ji, Q. Ji, Q. P. Ji, X. B. Ji, X. L. Ji, L. L. Jiang, X. S. Jiang, J. B. Jiao, Z. Jiao, D. P. Jin, S. Jin, F. F. Jing, N. Kalantar-Nayestanaki, M. Kavatsyuk, B. Kloss, B. Kopf, M. Kornicer, W. Kuehn, W. Lai, J. S. Lange, M. Lara, P. Larin, M. Leyhe, C. H. Li, Cheng Li, Cui Li, D. L. Li, D. M. Li, F. Li, G. Li, H. B. Li, J. C. Li, K. Li, Lei Li, N. Li, P. R. Li, Q. J. Li, W. D. Li, W. G. Li, X. L. Li, X. N. Li, X. Q. Li, X. R. Li, Z. B. Li, H. Liang, Y. F. Liang, Y. T. Liang, G. R. Liao, D. X. Lin, B. J. Liu, C. L. Liu, C. X. Liu, F. H. Liu, Fang Liu, Feng Liu, H. B. Liu, H. H. Liu, H. M. Liu, J. P. Liu, K. Liu, K. Y. Liu, P. L. Liu, Q. Liu, S. B. Liu, X. Liu, Y. B. Liu, Z. A. Liu, Zhiqiang Liu, Zhiqing Liu, H. Loehner, X. C. Lou, G. R. Lu, H. J. Lu, J. G. Lu, X. R. Lu, Y. P. Lu, C. L. Luo, M. X. Luo, T. Luo, X. L. Luo, M. Lv, F. C. Ma, H. L. Ma, Q. M. Ma, S. Ma, T. Ma, X. Y. Ma, F. E. Maas, M. Maggiora, Q. A. Malik, Y. J. Mao, Z. P. Mao, J. G. Messchendorp, J. Min, T. J. Min, R. E. Mitchell, X. H. Mo, H. Moeini, C. Morales Morales, K. Moriya, N. Yu Muchnoi, H. Muramatsu, Y. Nefedov, I. B. Nikolaev, Z. Ning, S. Nisar, S. L. Olsen, Q. Ouyang, S. Pacetti, J. W. Park, M. Pelizaeus, H. P. Peng, K. Peters, J. L. Ping, R. G. Ping, R. Poling, E. Prencipe, M. Qi, S. Qian, C. F. Qiao, L. Q. Qin, X. S. Qin, Y. Qin, Z. H. Qin, J. F. Qiu, K. H. Rashid, C. F. Redmer, M. Ripka, G. Rong, X. D. Ruan, A. Sarantsev, S. Schumann, W. Shan, M. Shao, C. P. Shen, X. Y. Shen, H. Y. Sheng, M. R. Shepherd, W. M. Song, X. Y. Song, S. Spataro, B. Spruck, G. X. Sun, J. F. Sun, S. S. Sun, Y. J. Sun, Y. Z. Sun, Z. J. Sun, Z. T. Sun, C. J. Tang, X. Tang, I. Tapan, E. H. Thorndike, D. Toth, M. Ullrich, I. Uman, G. S. Varner, B. Wang, D. Wang, D. Y. Wang, K. Wang, L. L. Wang, L. S. Wang, M. Wang, P. Wang, P. L. Wang, Q. J. Wang, S. G. Wang, X. F. Wang, X. L. Wang, Y. D. Wang, Y. F. Wang, Y. Q. Wang, Z. Wang, Z. G. Wang, Z. H. Wang, Z. Y. Wang, D. H. Wei, J. B. Wei, P. Weidenkaff, Q. G. Wen, S. P. Wen, M. Werner, U. Wiedner, L. H. Wu, N. Wu, S. X. Wu, W. Wu, Z. Wu, L. G. Xia, Y. X. Xia, Z. J. Xiao, Y. G. Xie, Q. L. Xiu, G. F. Xu, Q. J. Xu, Q. N. Xu, X. P. Xu, Z. R. Xu, Z. Xue, L. Yan, W. B. Yan, W. C. Yan, Y. H. Yan, H. X. Yang, Y. Yang, Y. X. Yang, Y. Z. Yang, H. Ye, M. Ye, M. H. Ye, B. X. Yu, C. X. Yu, H. W. Yu, J. S. Yu, S. P. Yu, C. Z. Yuan, W. L. Yuan, Y. Yuan, A. A. Zafar, A. Zallo, S. L. Zang, Y. Zeng, B. X. Zhang, B. Y. Zhang, C. Zhang, C. B. Zhang, C. C. Zhang, D. H. Zhang, H. H. Zhang, H. Y. Zhang, J. Q. Zhang, J. W. Zhang, J. Y. Zhang, J. Z. Zhang, Lili Zhang, S. H. Zhang, X. J. Zhang, X. Y. Zhang, Y. Zhang, Y. H. Zhang, Z. P. Zhang, Z. Y. Zhang, Zhenghao Zhang, G. Zhao, J. W. Zhao, Lei Zhao, Ling Zhao, M. G. Zhao, Q. Zhao, S. J. Zhao, T. C. Zhao, X. H. Zhao, Y. B. Zhao, Z. G. Zhao, A. Zhemchugov, B. Zheng, J. P. Zheng, Y. H. Zheng, B. Zhong, L. Zhou, X. Zhou, X. K. Zhou, X. R. Zhou, K. Zhu, K. J. Zhu, X. L. Zhu, Y. C. Zhu, Y. S. Zhu, Z. A. Zhu, J. Zhuang, B. S. Zou, J. H. Zou

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We study e+e- → π+π-hc at center-of-mass energies from 3.90 to 4.42 GeV by using data samples collected with the BESIII detector operating at the Beijing Electron Positron Collider. The Born cross sections are measured at 13 energies and are found to be of the same order of magnitude as those of e+e- → π+π-J/ψ but with a different line shape. In the π±hc mass spectrum, a distinct structure, referred to as Zc(4020), is observed at 4.02 GeV/c2. The Zc(4020) carries an electric charge and couples to charmonium. A fit to the π±hc invariant mass spectrum, neglecting possible interferences, results in a mass of (4022.9 ± 0.8 ± 2.7) MeV/c2 and a width of (7.9 ± 2.7 ± 2.6) MeV for the Zc(4020), where the first errors are statistical and the second systematic. The difference between the parameters of this structure and the Zc(4025) observed in the D∗ D∗ final state is within 1.5σ, but whether they are the same state needs further investigation. No significant Zc(3900) signal is observed, and upper limits on the Zc(3900) production cross sections in π±hc at center-of-mass energies of 4.23 and 4.26 GeVare set.

Original languageEnglish (US)
Article number242001
JournalPhysical Review Letters
Issue number24
StatePublished - Dec 10 2013

Bibliographical note

Funding Information:
The BESIII Collaboration thanks the staff of BEPCII and the computing center for their strong support. This work is supported in part by the Ministry of Science and Technology of China under Contract No. 2009CB825200; National Natural Science Foundation of China (NSFC) under Contracts No. 10625524, No. 10821063, No. 10825524, No. 10835001, No. 10935007, No. 11125525, and No. 11235011; Joint Funds of the National Natural Science Foundation of China under Contracts No. 11079008, No. 11079023, No. 11179007, and No. U1332201; the Chinese Academy of Sciences (CAS) Large-Scale Scientific Facility Program; CAS under Contracts No. KJCX2-YW-N29 and No. KJCX2-YWN45; 100 Talents Program of CAS; German Research Foundation DFG under Collaborative Research Center Contract No. CRC-1044; Istituto Nazionale di Fisica Nucleare, Italy; Ministry of Development of Turkey under Contract No. DPT2006K-120470; U.S. Department of Energy under Contracts No. DE-FG02-04ER41291, No. DE-FG02-05ER41374, and No. DE-FG02- 94ER40823; U.S. National Science Foundation; University of Groningen (RuG) and the Helmholtzzentrum fuer SchwerionenforschungGmbH (GSI), Darmstadt;WCU Program of National Research Foundation of Korea under Contract No. R32-2008-000-10155-0.

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© 2013 American Physical Society.

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