[formula presented] decay distributions

Using a sample of 3.8 M (Formula presented) events accumulated with the BES detector, the process (Formula presented) 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 amplitude, as well as S wave. On the other hand, the (Formula presented) 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 (Formula presented) predicts that D wave pions should be present. We determine (Formula presented) based on the joint (Formula presented) distribution. The fraction of D wave amplitude as a function of (Formula presented) is found to decrease with increasing (Formula presented) in agreement with the model. We have also fit the Mannel-Yan model, which is another model that allows D wave pions. © 2000 The American Physical Society.