Preliminary results of fission induced by (1068 MeV) pi(-) in Cu, Sn, Au and Bi using CR-39 detectors

Fission probabilities in pion induced reactions exhibit characteristic vari ations with respect to pion energies and target fissility values. At incide nt energies well above the pion-nucleon resonances, the statistical model s eems to give good description of the observed data. We have used negative p ions of energy 1068 MeV, in order to study fission induced in four target m aterials with fissility values [(Z-1)2/A] ranging from 12 to 32. All target s were arranged in a single stack in such a way that each target coated on a CR-39 detector was sandwiched by another uncoated CR-39 detector plate. T he stack was irradiated at the AGS of Brookhaven National Laboratory (USA). This set-up ensures solid angle coverage of almost 4 pi degrees, so that f or each fission event one of the fission fragments is expected to be trappe d by the forward detector and one by the detector covering backward hemisph ere. The effect of pion momentum transfer to the struck nucleus was observe d in the form of asymmetry between events counted in the two complementary detectors. The effect of target thickness on the number of tracks revealed in CR-39 has also been noted.