Coherent charge exchange of. pi. /sup +/ mesons on xenon nuclei at 2. 9 GeV/c

Photographs of a 120-liter bubble chamber filled with a propane--xenon mixture are used to provide an upper-limit estimate of the cross section for coherent charge exchange of ..pi../sup +/ mesons on xenon nuclei at a momentum 2.9 GeV/c. The value obtained is sigma/sub coh/ < or % 34..mu..b. (AIP)