Spin-Flip Scattering of Pions by Nuclei

Abstract

1563Inelastic scattering of pions from nuclei is discussed to give information on nuclear structure. The differential cross section at small angles is related to the beta and gamma transitions. Discussion is simplified for the spin-flip scattering. § I. IntroductionThe properties of pions are well known, and it is of interest to use them as probes for investigation of nuclear structure. In addition some more advantages of pions are the fact that the elementary pion-nucleon interaction up to kinetic energies of the order of 300 MeV is much better understood than the nucleonnucleon interaction, and that the small pion mass makes recoil corrections very small. Little is, however, observed about the inelastic scattering of pions leaving the target nucleus in individual excited states. Recently measurements of the differential cross sections for the inelastic scattering of pions on C 12 at energies near the 3-3 resonance have been reported by Binon et al. 1 l Their experiments could not resolve the individual nuclear levels at the excitation energies above '"'"'10 MeV. But this type of research with a high accuracy became possible through the development of research techniques.The purpose of this paper is to investigate general features of the inelastic scattering of pions on nuclei leading to the excitation of the discrete nuclear levels. We shall consider the spin-flip scattering which is clearly observed in pion scattering in detail, since the illustration of our discussion is simplified for this case, and some theoretical analysis on the non-flip scattering, relating it to (p, p') and (e, e') scattering, has appeared in the literature. 2 l As a related problem, it might be useful here to mention the inelastic scattering of high-energy protons by nuclei. It will help us to understand some features of scattering of pions. The angular distributions for the inelastic scattering leading to individual excited states can in general be classified into two categories; falling and rising cross sections at the forward angle. The spinflip scattering of protons, 3 l which belongs to the latter, results in a unique angular distribution with a maximum at 0°, and in contrast the spin-non-flip inelastic scattering except for the Coulomb excitation of the giant dipole resonance state has a at East Tennessee State University on June 22, 2015 http://ptp.oxfordjournals.org/ Downloaded from