Precise measurement of the e+e− →π+π−J/ψ cross section at center-of-mass energies from 3.77 to 4.60 GeV 后印本

摘要: 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+25.3−19.7 ± 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.