Positive-Pion Cross Sections on Complex Nuclei

Absorption and diffraction cross sections were measured for positive pions at a kinetic energy of 442 Mev. The target elements used were C, Al, Cu, and Cd. The absorption and diffraction cross sections were determined by fitting the experimental data (taken at six angles) to the shape given by the optical-model theory. The nuclear radius and the falloff parameter were taken to be approximately those determined from nuclear charge distribution measurements. The experimental data are compared with the results of the opticalmodel theory. Experimental values for the imaginary part of the potential VI are in agreement with the theoretical value. However, the experimental values for the real potential VR increase with increasing atomic number, becoming far larger than the theoretical value.