An upper limit on the decay rate of K??L-> pi+ pi- gamma

In the film from a spark chamber, experiment on KL decays performed in the 280 beam line of the ZGS at the Argonne National Laboratory" we undertook a search for the decay mode K??L-> pi+ pi- gamma The charged decay products were momentum analyzed in a magnet and identified in a set of range-shower chambers on the basis of their behavior there. The position of the gamma ray conversion point in these chambers was compared with the position predicted on the hypothesis of K??L-> pi+ pi- gamma. The Kpi3 provided almost the sole background as well: as the normalization of our rate measurement. In 962 events with good gamma showers we found one event fitted the 1(1(r hypothesis within our spacial resolution. However, the expected background was one event. This.,result corresponds to an upper limit on the decay rate [reaction] sec -1 at a confidence level of 9O%. The result is compared with the predictions of various theoretical models. The possible connections to other decay processes [reaction] and the feasibilities of CP invariance tests are discussed.U of I OnlyThesi