Radiative Decays of the Psi Prime to All-Photon Final States
Results of studies of selected radiative decays of the (psi)' to charmonium and non-charmonium states which decay into photons are presented. These studies were performed using a sample of 1.8 x 10('6) produced (psi)''s collected by the Crystal Ball detector at the SPEAR electron-positron storage ring. In the first study, the branching ratios of the (chi)(,0), (chi)(,2), and (eta)(,c)' to two photons have been measured to be (4.5 (+OR-) 2.2 (+OR-) 2.0) x 10(' -4), (9.5 (+OR-) 2.9 (+OR-) 4.5) x 10('-4) (first errors statistical, second systematic), and < 1 x 10('-2) (90% C.L.), respectively. (The statistical significance of the (chi)(,0) signal is slightly less than three standard deviations.) The signal from the decay chain (psi)' (- -->) (gamma)(chi)(,0), (chi)(,0) (--->) (pi)('0)(pi)('0) has been observed with essentially no background. Using the observed line shape of the radiative photon in this reaction, the full width of the (chi)(,0) has been found to be 8.8 (+OR-) 1.3 (+OR-) 1.5 MeV/c('2). In addition, the branching ratios of the (chi)(,0) and (chi)(,2) to (pi)('0)(pi)('0) have been measured to be (3.5 (+OR-) 0.3 (+OR-) 1.2) x 10('-3) and (1.2 (+OR-) 0.2 (+OR-) 0.4) x 10('-3), respectively; the branching ratios of the (chi)(,0) and (chi)(,2) to (eta)(eta) have been measured to be (2.8 (+OR-) 0.9 (+OR-) 1.3) x 10('-3) and (8.4 (+OR-) 4.2 (+OR -) 4.0) x 10('-4). In the second study, the decays of the (psi)' to four non-charmonium states have been investigated. The branching ratios and upper limits of these decays have been normalized to the branching ratios of the corresponding decays from the J/(psi) which have been measured using a sample of 2.2 x 10('6) produced J/(psi)'s collected by the Crystal Ball detector. The ratios of the (psi)' branching ratios to the J/(psi) branching ratios for the final states (gamma)(eta), (gamma)(eta)', (gamma)(theta), and (gamma)f have been measured to be <1.8%, <2.6%, <10-15%, and 9 (+OR -) 3%, respectively. (Upper limits are 90% confidence level. The upper limit for the radiative decay to the (theta) is poorly determined due to the uncertainty in the f' contribution in the J/(psi) data.). These results are compared with the theoretical expectations of lowest-order quantum chromodynamics potential models. Substantial disagreement is found between theory and experiment for the (chi)(,0) two photon branching ratio and full width, and the ratio of branching ratios upper limits for the (gamma)(eta) and (gamma)(eta)' final states.
- Pub Date:
- Physics: Elementary Particles and High Energy