π+N→N* production in the quark model

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  • パイ N N production in the quark model

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The cross section for the rc+ N-->N* production is calculated m the quark model using the static approximation for quarks. It is assumed that the incident pion is absorbed by a quark in the nucleon, resulting in the excitation of the nucleon. The main results are that the extension of the nucleon wave function is about 2.0"-'3.5 Ge v- 1 and that the coupling constant of the pion with the quark is f 2qqn/4rc"""0.3. The ratio of the cross section of the process passing through the resonance N* to the total cross section is also roughly given. The selection rule for the orbital angular momentum of the incident pion is obtained and agrees well with the experiment. yet been established. This problem is thought to be closely related with the internal structure of particles. The keys to elucidate the structure of particles from the aspect of reactions are being prepared. In 1956, the Sakata modeP) was proposed, where all particles were assumed to be composed of three existing particles : p, n, A. However, this model failed to classify the baryons. Afterwards, adopting the merits of the Sakata model, the study of elementary particles was developed on the basis of the theory of unitary group. s) First of all, static properties of elementary particles such as the classification of them, mass formula, ratio of magnetic moments and so on were well explained in terms of the unitary group. Then, that theory was applied to the dynamical aspect such as reactions, and the relations among the total cross sections of elementary-particle collisions were obtained. 4 ) Those relations were also explained by the quark modeP) and an additivity assump­ tion about scattering amplitudes. The additivity assumption 6 ) implies that hadron­ hadron scattering can be represented by the superposition of constituent quark­ quark scattering. This assumption neglects the cloud effects of elementary particles and supposes the impulse approximation for the interaction between quarks. In this paper, the production of the nucleon resonances "N*" by n-N col­ lisions are investigated in the light of the quark model. Here, nucleons and

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