Pion-nuclear scattering

Abstract

The last ten years have seen impressive progress in the field of pion-nuclear interactions thanks to the vast efforts at the meson factories LAMPF (Los Alamos), PSI/SIN in Villigen (Switzerland) and TRIUMF (Vancouver). Pion physics has attacked and highlighted problems of fundamental nature, of conventional nuclear structure and of a more specific nature. A huge amount of data has been gathered on pion-nucleon scattering, pion-nucleus scattering, pion absorption and single and double-charge exchange scattering.In the present paper pion-nuclear scattering is reviewed emphasizing basic interactions and symmetries. It will be outlined that (while pions are still regarded widely as an exotic probe in nuclear physics studies) it has become clear in recent years that those investigations have reached their maturity and have become competitive with, and are complementary to, nuclear studies by means of more familiar probes like electrons, protons etc. Pion physics has improved our understanding of nuclear physics by more accurate experiments using better beams and more sophisticated techniques and superior equipment, by extremely complex theoretical calculations available promptly in response to the latest experimental results, and by discoveries which have yielded really new and surprising insight into many questions.Topics of fundamental interest in the future will certainly be how to elucidate the role that the pion plays when it interacts with nuclei in terms of its connection to chiral symmetry and the dynamical breaking of the latter or how can pion physics contribute to questions that are asked under the guidance of QC:D.

Nuclear sigma term in the Skyrme model: Pion-nucleus interaction

“…MeV that is roughly of the same order necessary to fit the pionic atoms ( ≈15 to 30 MeV) and is "weakly dependent of A" [30].…”

“…Results for the isoscalar parameter of the optical potential including the potential sigma term contribution in Eq. (30). The 12 C and 16 O experimental values were estimated from the analysis described in Ref.…”

“…We constructed Table III using the results of the potential and kinetic energy contributions to the sigma term in Eq. (30) . The experimental results were extracted from pionic atoms and pion-nucleus scattering analysis [10,11] .…”

“…¿From Kluge[30]: "The conclusion is that this repulsion cannot be obtained by an iteration of πN interaction, but rather represents an independent feature of the interaction of pions with bulk nuclear matter. An attempt to explain this as a binding effect of the nucleons has been undertaken in the framework of relativistic mean field theory of the nucleus (Birbair et al 1983 J.Phys.G: Nucl.Phys 9 1473; Goudsmit et al 1989 Preprint ETHZ-IMP RP-90-03 ETH Zürich)"…”

Analysis of data on low energy πN → ππN reaction I. Total cross sections

“…The problem of the extraction of low energy ππ -interaction parameters with a desirable accuracy looks, in such a situation, extremely difficult. At the same time, the successive resolution of this problem is important by its own, irrespective of the following application of the results: the pion, which is the lightest hadron, participates -really or virtually -in every strong interaction process (see, for example, [28,31,32]). This is a reason why the complete phenomenological analysis of the data on low energy πN → ππN reaction is really of actual interest.…”