Observation of a Charged Charmoniumlike StructureZc(4020)and Search for theZc(3900)ine+e−→π+π−hc

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

doi:10.1103/physrevlett.111.242001

Abstract

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[over ¯]* 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 GeV are set.

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