Observation of hc radiative decay hc › ??' and evidence for hc › ??

Abstract

A search for radiative decays of the P-wave spin singlet charmonium resonance hc is performed based on 4.48 × 108 ? events collected with the BESIII detector operating at the BEPCII storage ring. Events of the reaction channels hc › ??' and ?? are observed with a statistical significance of 8.4? and 4.0?, respectively, for the first time. The branching fractions of hc › ??' and hc › ?? are measured to be B(hc › ??' ) = (1.52±0.27±0.29)×10-3 and B(hc › ??) = (4.7±1.5±1.4)×10-4 , respectively, where the first errors are statistical and the second are systematic uncertainties.