Precise Measurement of the e⁺e⁻ → π⁺π⁻J/ψ Cross Section at Center-of-Mass Energies from 3.77 To 4.60 GeV


The cross section for the process e⁺e⁻ → π⁺π⁻J/ψ is measured precisely at center-of-mass energies from 3.77 to 4.60 GeV using 9 fb⁻¹ of data collected with the BESIII detector operating at the BEPCII storage ring. Two resonant structures are observed in a fit to the cross section. The first resonance has a mass of (4222.0 ± 3.1 ± 1.4) MeV/c² and a width of (44.1 ± 4.3 ± 2.0) MeV, while the second one has a mass of (4320.0 ± 10.4 ± 7.0) MeV/c² and a width of (101.4_{-19.7} ^{+25.3} ± 10.2) MeV, where the first errors are statistical and second ones are systematic. The first resonance agrees with the Y(4260) resonance reported by previous experiments. The precision of its resonant parameters is improved significantly. The second resonance is observed in e⁺e⁻ → π⁺π⁻J/ψ for the first time. The statistical significance of this resonance is estimated to be larger than 7.6σ. The mass and width of the second resonance agree with the Y(4360) resonance reported by the BABAR and Belle experiments within errors. Finally, the Y(4008) resonance previously observed by the Belle experiment is not confirmed in the description of the BESIII data.


Includes supplementary material


Statistical hypothesis testing, Resonance, Center of mass

This work is supported in part by National Key Basic Research Program of China under Contract No. 2015CB856700; National Natural Science Foundation of China (NSFC) under Contracts No. 11235011, No. 11322544, No. 11335008, and No. 11425524; Joint Large-Scale Scientific Facility Funds of the NSFC and CAS under Contracts No. U1232201 and No. U1332201; CAS under Contracts No. KJCX2-YW-N29 and No. KJCX2-YW-N45; German Research Foundation DFG under Collaborative Research Center Contracts No. CRC 1044 and No. FOR 2359; Seventh Framework Programme of the European Commission under Marie Curie International Incoming Fellowship Grant Agreement No. 627240; Joint Large-Scale Scientific Facility Funds of the NSFC and CAS under Contract No. U1532257; Joint Large-Scale Scientific Facility Funds of the NSFC and CAS under Contract No. U1532258; Koninklijke Nederlandse Akademie van Wetenschappen (KNAW) under Contract No. 530-4CDP03; Ministry of Development of Turkey under Contract No. DPT2006K-120470; NSFC under Contract No. 11275266; The Swedish Resarch Council; U.S. Department of Energy under Contracts No. DE-FG02-05ER41374, No. DE-SC-0010504, No. DE-SC0012069, and No. DESC0010118; WCU Program of National Research Foundation of Korea under Contract No. R32-2008-000-10155-0.


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