Evidence for resonant structures in e+e−→π+π−hc

Abstract

The cross sections of e+e−→π+π−hc at center-of-mass energies from 3.90 to 4.42 GeV were measured by the BESIII and the CLEO-c experiments. Resonant structures are evident in the e+e−→π+π−hc line shape. The fit to the line shape results in a narrow structure at a mass of (4216±18) MeV/c2 and a width of (39±32) MeV, and a possible wide structure of mass (4293±9) MeV/c2 and width (222±67) MeV. Here, the errors are combined statistical and systematic errors. This may indicate that the Y(4260) state observed in e+e−→π+π−J/ψ has a fine structure in it.