Psi(2S) -> pi^+ pi^- J/psi Decay Distributions

Abstract

Using a sample of 3.8 M psi(2S) events accumulated with the BES detector, the process psi(2S) -> pi^+ pi^- J/psi is studied. The angular distributions are compared with the general decay amplitude analysis of Cahn. We find that the dipion system requires some D-wave, as well as S-wave. On the other hand, the J/psi-(pi pi) relative angular momentum is consistent with being pure S-wave. The decay distributions have been fit to heavy quarkonium models, including the Novikov-Shifman model. This model, which is written in terms of the parameter kappa, predicts that D-wave should be present. We determine kappa = 0.183 +/- 0.002 +/- 0.003 based on the joint dipion mass - cos theta distribution. The fraction of D-wave as a function of the dipion mass is found to decrease with increasing dipion mass, in agreement with the model. We have also fit the Mannel-Yan model, another model that allows D-wave.