The properties of the ψ"(3770) were studied by an experiment performed at the SPEAR e+e- colliding beam facility using the Crystal Ball detector. The unique abilities of the Crystal Ball, a highly segmented NaI detector that specializes in precisely measuring the energy and direction of photons, were used to make several new measurements.
The hadron cross section was measured at 23 different center of mass energies in the vicinity of the ψ". The ψ" is clear1y visib1e as a peak in the cross section near Ecm = 3770 MeV. The ψ" resonance parameters were determined by fitting a modified Breit-Wigner line shape to the observed hadron cross section. The ψ" mass, partial width to e+e-, and total width were measured to be 3768±5 MeV, 283±70 eV, and 34±8 MeV, respectively.
The inclusive photon spectrum of the ψ" was examined for structure. Harrow peaks were observed in the spectrum due to the radiative production of ψ and ψ' mesons. The integrated hadron cross sections were measured to be 16±5 nb-GeV and 5.2±1.7 nb-Gev for the ψ and ψ', respectively. No other statistically significant structure was observed.
The decays of the ψ" were used to search for D° mesons decaying into four-photon and six-photon final states. No evidence for these decays was found, and the following branching ratio limits were set (90% CL): BR(D° → π°π°) < 0.28%, BR(D°→ η°π°) < 0.74%, BR(D° → ηη) < 1.0%., BR(D°→π°π°π°) < 1.6%, BR(D° → ηπ°π°) < 6.6%, and BR(D° → K°π°) < 7.6%.
