Pion, pion-pion, and pion-nucleus interactions

Abstract

This survey is devoted to describing the early studies of I.I. Gurevich on pion physics that were performed by the photoemulsion method and the studies of the pion-pion interaction that were made by his colleagues on the basis of the hydrogen-bubble-chamber and the magnetic-spectrometer method (as well as on the basis of the photoemulsion method). Two approaches—an extrapolation of experimental data from the physical region to the pion pole and a theoretical calculation based on the Roy integral equations—are used to deduce information about the pion-pion interaction. The first results obtained for pion-pion and pion-nucleus interactions in the experiments that are being currently performed in Brookhaven and at CERN (ππ interaction) and at TRIUMF (Canada) and in Brookhaven (pion-nucleus interaction) are presented, along with the existing theoretical concepts in these realms of physics.