Duality and resonances

Abstract

The main idea of the following pages is to review the A (_1) partical. They set out to explain the problem, to show the attempts done in this field and to compare the different interpretations of different authors. In order to do this we use resonances and duality as our tools of investigation. In chapter one, we give a general discussion on resonances. We show what we mean by a resonance, what the characteristics of resonances may be, and the ways by which resonances are determined. Some mis-leading terminologies and interpretations which occur in this area are also discussed. In the second part, an explanation of SU(2), SU(3) and quark models has been done. There, the concept of exotic states and their different types are shown. In chapter two, a sketch of the A (_1) particale, since the time it was discovered till the recent time when different types of models have been given in order to resolve or, at least, to clarify and explain the mysterie of the πρ enhancement is drawn. Also the A (_1’s) future and a simple test, which invokes data to remove the A (_1) ambiguity are given. In chaprte three, the idea of duality has been discussed. How duality has altered the concept of resonances, what the conflict with the earlier interference model is, the Veneziano model and finaly the effect of duality on the A (_1) problem are discussed. In chapter four, we extend the discussion of chapter three. The excellent discussion by E.L. Berger (1971) is given here. His suggested model may make the situation of the A (_1) clear. His discussion encourages people to believe that the A (_1) might be a kinematical effect. Finally, we conclude by giving a brief review of the present status of the A (_1) enhancement.