Three Properties of Nonleptonic Hyperon Decays*)

The nonleptonic hyperon decay has the following three properties: I) the! JI! = 1/2 rule holds, II) i).s+-~n+n+ is the pure p-wave decay, ii).s--7n+n- is the pure s-wave decay, and III) the triangle relation of Lee and Sugawara holels. In this paper we discuss the fol-lowing problems: Does there exist such a simple model which can give a theoretical basis for these three properties? If it does not exist yet, then how can we construct the required model? For this purpose, we take up four typical examples of models: (I) Pole model, (II) Current algebra model, (III) [J (12) symmetry model and (rV) Composite model. It has turned out that no model succeeds in explaining all of the three properties. In particular, the existing models fail to obtain g_=O without parameter-fitting. Therefore, whenever one tries to construct a new model on the nonleptonic decay, one must begin with searching how to obtain g-=O