Pion-Nucleus Microscopic Optical Potential at Intermediate Energies and In-Medium Effect on the Elementary π N Scattering Amplitude
Abstract
Analysis is performed of calculations of the elastic scattering differential cross sections of pions on the 28Si, 40Ca, 58Ni and 208Pb nuclei at energies from 130 to 290 MeV basing on the microscopic optical potential (OP) constructed as an optical limit of a Glauber theory. Such an OP is defined by the corresponding target nucleus density distribution function and by the elementary π N amplitude of scattering. The three (say, "in-medium") parameters of the π N scattering amplitude: total cross section, the ratio of real to imaginary part of the forward π N amplitude, and the slope parameter, were obtained by fitting them to the data on the respective pion-nucleus cross sections calculated by means of the corresponding relativistic wave equation with the above OP. A difference is discussed between the best-fit "in-medium" parameters and the "free" parameters of the π N scattering amplitudes known from the experimental data on scattering of pions on free nucleons.