We study the process e+e- → pi+pi-ψ(3686) using 5.1 fb−1 of data collected at 16 center-of-mass energy ( sqrt(s)) points from 4.008 to 4.600 GeV by the BESIII detector operating at the BEPCII collider. The measured Born cross sections for e+e− → pi+pi−ψ(3686) are consistent with previous results, but with much improved precision. A fit to the cross section shows contributions from two structures: the first has M=4209.5 pm 7.4 pm 1.4 MeV/c2 andΓ=80.1 pm 24.6 pm 2.9MeV,and the second has M=4383.8 pm 4.2 pm 0.8 MeV/c2 and Γ = 84.2 pm 12.5 pm 2.1 MeV, where the first errors are statistical and the second systematic. The lower-mass resonance is observed in the process e+e− → pi+pi−ψ(3686) for the first time with a statistical significance of 5.8 sigma. A charged charmoniumlike structure is observed in the π(+-)ψ(3686) invariant mass spectrum for data at sqrt(s) = 4.416 GeV. A fit with an S-wave Breit-Wigner function yields a mass M = 4032.1 pm 2.4 MeV/c2, where the errors are statistical only. However, there are still unresolved discrepancies between the fit model and data. The width of the intermediate state varies in a wide range for different kinematic regions within the data set. Therefore, no simple interpretation of the data has been found, and a future data sample with larger statistics and more theoretical input will be required to better understand this issue.
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|Titolo:||Measurement of e+e−→π+π−ψ(3686) from 4.008 to 4.600 GeV and observation of a charged structure in the π±ψ(3686) mass spectrum|
|Data di pubblicazione:||2017|
|Appare nelle tipologie:||03.1 Articolo su rivista|