ISSN - 00319007, EISSN - 10797114, Physical Review Letters, 2014, vol. 113, p. -
Observation of e+e- →π0π0hc and a Neutral Charmoniumlike Structure Zc (4020)0
© 2014 American Physical Society. 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 4.02GeV/c2 is found. It is most likely to be the neutral isospin partner of the Zc(4020)± observed in the process of e+e-→π+π-hc being 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.