Observation of e +e − → π 0π 0hc and a neutral charmoniumlike structure Zc(4020)0
CitationKolcu, O.B. (2014). Observation of e +e − → π 0π 0hc and a neutral charmoniumlike structure Zc(4020)0. Physical Review Letters, 1-7.
Using data collected with the BESIII detector operating at the Beijing Electron Positron Collider at center-of-mass energies of s√=4.23, 4.26, and 4.36 GeV, we observe e+e−→π0π0hc for the first time. The Born cross sections are measured and found to be about half of those of e+e−→π+π−hc within less than 2σ. In the π0hc mass spectrum, a structure at 4.02~GeV/c2 that is most likely the neutral isospin partner of the Zc(4020)± observed in the process of e+e−→π+π−hc is found. A fit to the π0hc invariant mass spectrum with the width of the Zc(4020)0 fixed to that of its charged isospin partner and possible interferences with non-Zc(4020)0 amplitudes neglected, gives a mass of (4023.9±2.2±3.8)~MeV/c2 for the Zc(4020)0, where the first error is statistical and the second systematic.