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Phys Rev Lett. 2016 Jul 22;117(4):042002. doi: 10.1103/PhysRevLett.117.042002. Epub 2016 Jul 21.

Observation of an Anomalous Line Shape of the η^{'}π^{+}π^{-} Mass Spectrum near the pp[over ¯] Mass Threshold in J/ψ→γη^{'}π^{+}π^{-}.

Ablikim M1, Achasov MN2, Ahmed S3, Ai XC1, Albayrak O4, Albrecht M5, Ambrose DJ6, Amoroso A7,8, An FF1, An Q9, Bai JZ1, Baldini Ferroli R10, Ban Y11, Bennett DW12, Bennett JV4, Berger N13, Bertani M10, Bettoni D14, Bian JM15, Bianchi F7,8, Boger E16, Boyko I16, Briere RA4, Cai H17, Cai X1, Cakir O18, Calcaterra A10, Cao GF1, Cetin SA19, Chang JF1, Chelkov G16, Chen G1, Chen HS1, Chen HY20, Chen JC1, Chen ML1, Chen S21, Chen SJ22, Chen X1, Chen XR23, Chen YB1, Cheng HP24, Chu XK11, Cibinetto G14, Dai HL1, Dai JP25, Dbeyssi A3, Dedovich D16, Deng ZY1, Denig A13, Denysenko I16, Destefanis M7,8, De Mori F7,8, Ding Y26, Dong C27, Dong J1, Dong LY1, Dong MY1, Dou ZL22, Du SX28, Duan PF1, Fan JZ29, Fang J1, Fang SS1, Fang X9, Fang Y1, Farinelli R14,30, Fava L31,8, Fedorov O16, Feldbauer F13, Felici G10, Feng CQ9, Fioravanti E14, Fritsch M3,13, Fu CD1, Gao Q1, Gao XL9, Gao XY20, Gao Y29, Gao Z9, Garzia I14, Goetzen K32, Gong L27, Gong WX1, Gradl W13, Greco M7,8, Gu MH1, Gu YT33, Guan YH1, Guo AQ1, Guo LB34, Guo RP1, Guo Y1, Guo YP13, Haddadi Z35, Hafner A13, Han S17, Hao XQ36, Harris FA37, He KL1, Heinsius FH5, Held T5, Heng YK1, Holtmann T5, Hou ZL1, Hu C34, Hu HM1, Hu JF7,8, Hu T1, Hu Y1, Huang GS9, Huang YP1, Huang JS36, Huang XT38, Huang XZ22, Huang Y22, Huang ZL26, Hussain T39, Ji Q1, Ji QP27, Ji XB1, Ji XL1, Jiang LW17, Jiang XS1, Jiang XY27, Jiao JB38, Jiao Z24, Jin DP1, Jin S1, Johansson T40, Julin A15, Kalantar-Nayestanaki N35, Kang XL1, Kang XS27, Kavatsyuk M35, Ke BC4, Kiese P13, Kliemt R3, Kloss B13, Kolcu OB19, Kopf B5, Kornicer M37, Kupsc A40, Kühn W41, Lange JS41, Lara M12, Larin P3, Leithoff H13, Leng C8, Li C40, Li C9, Li DM28, Li F1, Li FY11, Li G1, Li HB1, Li HJ1, Li JC1, Li J42, Li K43, Li K38, Li L44, Li PR21, Li QY38, Li T38, Li WD1, Li WG1, Li XL38, Li XN1, Li XQ27, Li YB20, Li ZB45, Liang H9, Liang YF46, Liang YT41, Liao GR47, Lin DX3, Liu B25, Liu BJ1, Liu CX1, Liu D9, Liu FH48, Liu F1, Liu F49, Liu HB33, Liu HH1, Liu HH50, Liu HM1, Liu J1, Liu JB9, Liu JP17, Liu JY1, Liu K29, Liu KY26, Liu LD11, Liu PL1, Liu Q21, Liu SB9, Liu X23, Liu YB27, Liu YY27, Liu ZA1, Liu Z13, Loehner H35, Lou XC1, Lu HJ24, Lu JG1, Lu Y1, Lu YP1, Luo CL34, Luo MX51, Luo T37, Luo XL1, Lyu XR21, Ma FC26, Ma HL1, Ma LL38, Ma MM1, Ma QM1, Ma T1, Ma XN27, Ma XY1, Ma YM38, Maas FE3, Maggiora M7,8, Malik QA39, Mao YJ11, Mao ZP1, Marcello S7,8, Messchendorp JG35, Mezzadri G30, Min J1, Min TJ1,21, Mitchell RE12, Mo XH1, Mo YJ49, Morales Morales C3, Muchnoi NY2, Muramatsu H15, Musiol P5, Nefedov Y16, Nerling F3, Nikolaev IB2, Ning Z1, Nisar S52, Niu SL1, Niu XY1, Olsen SL42, Ouyang Q1, Pacetti S53, Pan Y9, Patteri P10, Pelizaeus M5, Peng HP9, Peters K32, Pettersson J40, Ping JL34, Ping RG1, Poling R15, Prasad V1, Qi HR20, Qi M22, Qian S1, Qiao CF21, Qin LQ38, Qin N17, Qin XS1, Qin ZH1, Qiu JF1, Rashid KH39, Redmer CF13, Ripka M13, Rong G1, Rosner Ch3, Ruan XD33, Sarantsev A16, Savrié M30, Schnier C5, Schoenning K40, Schumann S13, Shan W11, Shao M9, Shen CP20, Shen PX27, Shen XY1, Sheng HY1, Shi M1, Song WM1, Song XY1, Sosio S7,8, Spataro S7,8, Sun GX1, Sun JF36, Sun SS1, Sun XH1, Sun YJ9, Sun YZ1, Sun ZJ1, Sun ZT12, Tang CJ46, Tang X1, Tapan I54, Thorndike EH6, Tiemens M35, Uman I55, Varner GS37, Wang B27, Wang BL21, Wang D11, Wang DY11, Wang K1, Wang LL1, Wang LS1, Wang M38, Wang P1, Wang PL1, Wang SG11, Wang W1, Wang WP9, Wang XF29, Wang Y56, Wang YD3, Wang YF1, Wang YQ13, Wang Z1, Wang ZG1, Wang ZH9, Wang ZY1, Wang ZY1, Weber T13, Wei DH47, Wei JB11, Weidenkaff P13, Wen SP1, Wiedner U5, Wolke M40, Wu LH1, Wu LJ1, Wu Z1, Xia L9, Xia LG29, Xia Y57, Xiao D1, Xiao H58, Xiao ZJ34, Xie YG1, Xiu QL1, Xu GF1, Xu JJ1, Xu L1, Xu QJ43, Xu QN21, Xu XP56, Yan L7,8, Yan WB9, Yan WC9, Yan YH57, Yang HJ25, Yang HX1, Yang L17, Yang YX47, Ye M1, Ye MH59, Yin JH1, Yu BX1, Yu CX27, Yu JS23, Yuan CZ1, Yuan WL22, Yuan Y1, Yuncu A19, Zafar AA39, Zallo A10, Zeng Y57, Zeng Z9, Zhang BX1, Zhang BY1, Zhang C22, Zhang CC1, Zhang DH1, Zhang HH45, Zhang HY1, Zhang J1, Zhang JJ1, Zhang JL1, Zhang JQ1, Zhang JW1, Zhang JY1, Zhang JZ1, Zhang K1, Zhang L1, Zhang SQ27, Zhang XY38, Zhang Y1, Zhang YH1, Zhang YN21, Zhang YT9, Zhang Y21, Zhang ZH49, Zhang ZP9, Zhang ZY17, Zhao G1, Zhao JW1, Zhao JY1, Zhao JZ1, Zhao L9, Zhao L1, Zhao MG27, Zhao Q1, Zhao QW1, Zhao SJ28, Zhao TC1, Zhao YB1, Zhao ZG9, Zhemchugov A16, Zheng B58, Zheng JP1, Zheng WJ38, Zheng YH21, Zhong B34, Zhou L1, Zhou X17, Zhou XK9, Zhou XR9, Zhou XY1, Zhu K1, Zhu KJ1, Zhu S1, Zhu SH60, Zhu XL29, Zhu YC9, Zhu YS1, Zhu ZA1, Zhuang J1, Zotti L7,8, Zou BS1, Zou JH1; BESIII Collaboration.

Author information

1
Institute of High Energy Physics, Beijing 100049, People's Republic of China.
2
G.I. Budker Institute of Nuclear Physics SB RAS (BINP), Novosibirsk 630090, Russia.
3
Helmholtz Institute Mainz, Johann-Joachim-Becher-Weg 45, D-55099 Mainz, Germany.
4
Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA.
5
Bochum Ruhr-University, D-44780 Bochum, Germany.
6
University of Rochester, Rochester, New York 14627, USA.
7
University of Turin, I-10125 Turin, Italy.
8
INFN, I-10125 Turin, Italy.
9
University of Science and Technology of China, Hefei 230026, People's Republic of China.
10
INFN Laboratori Nazionali di Frascati, I-00044 Frascati, Italy.
11
Peking University, Beijing 100871, People's Republic of China.
12
Indiana University, Bloomington, Indiana 47405, USA.
13
Johannes Gutenberg University of Mainz, Johann-Joachim-Becher-Weg 45, D-55099 Mainz, Germany.
14
INFN Sezione di Ferrara, I-44122 Ferrara, Italy.
15
University of Minnesota, Minneapolis, Minnesota 55455, USA.
16
Joint Institute for Nuclear Research, 141980 Dubna, Moscow region, Russia.
17
Wuhan University, Wuhan 430072, People's Republic of China.
18
Ankara University, 06100 Tandogan, Ankara, Turkey.
19
Istanbul Bilgi University, 34060 Eyup, Istanbul, Turkey.
20
Beihang University, Beijing 100191, People's Republic of China.
21
University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China.
22
Nanjing University, Nanjing 210093, People's Republic of China.
23
Lanzhou University, Lanzhou 730000, People's Republic of China.
24
Huangshan College, Huangshan 245000, People's Republic of China.
25
Shanghai Jiao Tong University, Shanghai 200240, People's Republic of China.
26
Liaoning University, Shenyang 110036, People's Republic of China.
27
Nankai University, Tianjin 300071, People's Republic of China.
28
Zhengzhou University, Zhengzhou 450001, People's Republic of China.
29
Tsinghua University, Beijing 100084, People's Republic of China.
30
University of Ferrara, I-44122 Ferrara, Italy.
31
University of Eastern Piedmont, I-15121 Alessandria, Italy.
32
GSI Helmholtzcentre for Heavy Ion Research GmbH, D-64291 Darmstadt, Germany.
33
GuangXi University, Nanning 530004, People's Republic of China.
34
Nanjing Normal University, Nanjing 210023, People's Republic of China.
35
KVI-CART, University of Groningen, NL-9747 AA Groningen, The Netherlands.
36
Henan Normal University, Xinxiang 453007, People's Republic of China.
37
University of Hawaii, Honolulu, Hawaii 96822, USA.
38
Shandong University, Jinan 250100, People's Republic of China.
39
University of the Punjab, Lahore-54590, Pakistan.
40
Uppsala University, Box 516, SE-75120 Uppsala, Sweden.
41
Justus-Liebig-Universitaet Giessen, II. Physikalisches Institut, Heinrich-Buff-Ring 16, D-35392 Giessen, Germany.
42
Seoul National University, Seoul 151-747, Korea.
43
Hangzhou Normal University, Hangzhou 310036, People's Republic of China.
44
Beijing Institute of Petrochemical Technology, Beijing 102617, People's Republic of China.
45
Sun Yat-Sen University, Guangzhou 510275, People's Republic of China.
46
Sichuan University, Chengdu 610064, People's Republic of China.
47
Guangxi Normal University, Guilin 541004, People's Republic of China.
48
Shanxi University, Taiyuan 030006, People's Republic of China.
49
Central China Normal University, Wuhan 430079, People's Republic of China.
50
Henan University of Science and Technology, Luoyang 471003, People's Republic of China.
51
Zhejiang University, Hangzhou 310027, People's Republic of China.
52
COMSATS Institute of Information Technology, Lahore, Defence Road, Off Raiwind Road, 54000 Lahore, Pakistan.
53
INFN and University of Perugia, I-06100 Perugia, Italy.
54
Uludag University, 16059 Bursa, Turkey.
55
Near East University, Nicosia, North Cyprus, Mersin 10, Turkey.
56
Soochow University, Suzhou 215006, People's Republic of China.
57
Hunan University, Changsha 410082, People's Republic of China.
58
University of South China, Hengyang 421001, People's Republic of China.
59
China Center of Advanced Science and Technology, Beijing 100190, People's Republic of China.
60
University of Science and Technology Liaoning, Anshan 114051, People's Republic of China.

Abstract

Using 1.09×10^{9} J/ψ events collected by the BESIII experiment in 2012, we study the J/ψ→γη^{'}π^{+}π^{-} process and observe a significant abrupt change in the slope of the η^{'}π^{+}π^{-} invariant mass distribution at the proton-antiproton (pp[over ¯]) mass threshold. We use two models to characterize the η^{'}π^{+}π^{-} line shape around 1.85  GeV/c^{2}: one that explicitly incorporates the opening of a decay threshold in the mass spectrum (Flatté formula), and another that is the coherent sum of two resonant amplitudes. Both fits show almost equally good agreement with data, and suggest the existence of either a broad state around 1.85  GeV/c^{2} with strong couplings to the pp[over ¯] final states or a narrow state just below the pp[over ¯] mass threshold. Although we cannot distinguish between the fits, either one supports the existence of a pp[over ¯] moleculelike state or bound state with greater than 7σ significance.

PMID:
27494467
DOI:
10.1103/PhysRevLett.117.042002
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