Measurements of selected psi /3684/ branching ratios from a study of secondary lepton pairs

The measurements considered were made at the electron-positron storage ring at the Stanford Linear Accelerator Center. The apparatus used consists of two identical spectrometers mounted in a collinear configuration about the beam-interaction region. The energies of secondary electrons or positrons are measured with good resolution in large NaI(Tl) total-absorption detectors. Data accumulated without gamma-ray converters were examined for electron-positron pairs. The data taken with gamma-ray converters in place and at center-of-mass energies within 1 MeV of the resonance energy were scanned for evidence of either charged particles or converted gamma rays accompanying the detected muon pairs.