(1068 MeV) pi bar induced fission in gold observed with CR-39 plastic track detectors

In this paper results of the study of (1068 MeV) negative pion induced fission in a gold have been presented. To detect the reaction products emitted in the forward as well as backward hemisphere, a 4 pi configuration of exposure geometry was made by sandwiching the target material (gold) between two pieces of CR-39 plastic track detectors. This target-detector assembly was exposed at normal incidence to (1068 MeV) pi having a fluence of 8.55 x 10/sup 8/ pions/cm/sup 2/ at Low Energy Pion (LEP) channel of Clinton P. Anderson Meson Physics Facility (LAMPF), Brookhaven National Laboratory, USA. After exposure the gold layer was removed using aqua regia and then both the detectors were etched in 6N NaOH at (70 -+ 1) deg. C for 25 minutes to reveal the tracks. The number of fission fragment tracks in both the detectors were counted. The number of fission tracks in the detector placed downstream of the incident pion beam were found to be greater than those in the detector placed upstream. This difference has been attributed to the transfer of momentum in the forward direction due to the impact of pions. Reaction cross section has been calculated by taking into account the track statistics of both the detectors. (authors)