Radiative decays of the psi prime to all-photon final states

Abstract

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/sup 6/ produced psi''s collected by the Crystal Ball detector at the SPEAR electron-positron storage ring. The branching ratios of the chi/sub 0/, chi/sub 2/, and eta'/sub c/ to two photons have been measured to be (4.5 +- 2.2 +- 2.0) x 10/sup -4/, (9.5 +- 2.9 +- 4.5) x 10/sup -4/ (first errors statistical, second systematic), and <1 x 10/sup -2/ (90% C.L.). The signal from the decay chain psi' ..-->.. ..gamma..chi/sub 0/, chi/sub 0/ ..-->.. ..pi../sup 0/..pi../sup 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 psi/sub 0/ has been found to be 8.8 +- 1.3 +- 1.5 MeV/c/sup 2/. In addition, the branching ratios of the chi/sub 0/ and chi/sub 2/ to ..pi../sup 0/..pi../sup 0/ have been measured to be (3.5 +- 0.3 +- 1.2) x 10/sup -3/ and (1.2 +- 0.2 +- 0.4) x 10/sup -3/; the branching ratios of the chi/sub 0/ and chi/sub 2/ to eta eta have been measured to be (2.8 +- 0.9 +- 1.3) x 10/sup -3/ and (8.4 +- 4.2 +- 4.0) x 10/sup -4/. 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/sup 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 to 15%, and 9 +- 3%. These results are compared with the theoretical expectations of lowest-order quantum chromodynamics potential models. Substantial disagreement is found between theory and experiment.