FINAL-STATE PI-PI INTERACTIONS IN UPSILON (3S)-]UPSILON(1S)PI-PI

The m(pipi) spectrum and various angular distributions in UPSILON(3S) --> UPSILON(1S) pipi are studied including the effects of the pipi pha se shift in the I = L = 0 channel using the lowest order amplitude in the pion momentum expansion. Our results are compared with the recent CLEO data, and we find good agreement except for the costheta(pi) dis tributions. We argue that the costheta(pi) distribution, contrary to other distributions, is sensitive to the higher order corrections in t he pion momentum expansion. This argument is supported by using an ans atz for the amplitude which is of higher order in the pion momentum ex pansion and still satisfies the soft pion theorem.