Three Properties of Nonleptonic Hyperon Decays

Abstract

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+nis the pure s-wave decay, and III) the triangle relation of Lee and Sugawara holels. In this paper we discuss the following 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.~ 1. Introduction Many attempts!) have been made to give a theoretical explanation of the nonleptonic decays of hadrons. In these attempts, the authors have spared no efforts to reproduce the experimental data on nonleptonic decays, but are apt to pay less attention to give a theoretical basis**) for the properties of the relevant decays. Thus some properties of the nonleptonic decays can only be explained as a result of the adjustment of free parameters in their model. For example, they fail to derive directly hom their model the property of the decay that the p-wave amplitude of };'--->Jl + rcvanishes, but can barely obtain the result consistent with this property by the adjustment o£ free parameters. Contrary, to the above attitude, in this paper, we should like to emphasize that it is necessary for us, first of all, to give a theoretical basis' for the properties of the decay, and as a next step, to proceed to a reproduction of the experimental data. This standpoint has already been proposed by Toda 2 ) in a recent paper. In this paper we discuss the follo\ving problems: Does there exist such a simple *) This is one of the works by the" Molecular Type" research group on nonleptonic decays, as a project of Research Institute for Fundamental Physics (Kyoto), Part of this work was reported by one of. the authors (A. T) at the Nleeting on the 1l0nlej.>Lonic decays, held at H.esearch Institute for Fundamental Physics (Kyoto), June 19G7. **) To give a "theoretical basis" means that the statement ((1.4») is given as a logical conclusion from basic assumptions in a model.'n This fact is also pointed out by M. lmoto and K. Ohya, preprint.

Characteristic Features in Nonleptonic Hyperon Decays and Composite Models

“…It is noticed that the conditions (A) and (B) for the parity-conserving and violating decays, ~espectively, are not only consistent with relative ratios of the experimental data but consistent with the signs of asymmetry parameters. Here, we have used the effective Hamiltonians of derivative type (2) from which the idealized data*) are obtained as pointed out by Imoto and Nakamura. 9 ) In Table II, we summarize the results derived from various selection rules: R-invariance 10 ) which denotes the invariance of the effective decay amplitudes under the transformations of B/~Bl, B/<~Bl and P/~P/; absence rule 11 > which asserts an amplitude with some SU(3) configurations to vanish; the Ikeda-Miyachi-Ogawa rule (I-M-0 ruleY 2 > requires that the initial and final states of decays are classified according to the representation of SU (3), which should be conserved; and "exchange symmetry "**)' 13 > in t-, s-and u-channels which indicate the invariance of the effective decay amplitudes under the transformations of…”