Un " tary Symmetry in Strong Interaction . II - - Excited States of Baryons

The purpose of this note is to investigate problems of baryon isobars from the viewpoint of the unitary symmetry model_ll In this model, the mass differences among mesons and among baryons are neglected. As the result, one may wonder if such a model can be applicable to the study of the baryon isobars which appear in the meson-baryon scattering, where these mass differences are certainly not negligible. It is almost probable that our model will present a very poor approximation for this problem if compared quantitatively. However, it might be possible that many of qualitative features could be roughly explained by our model. It is due to this hope that this work has been undertaken. So all results given in this paper should not be taken in its face value, but only in a qualitative sense. In this paper, we shall concern ourselves with the case of studies of Yamaguchi-Gell-Mann scheme/l since the case of the Sakata scheme has been treated already1J,BJ and would not produce any new results. We may note that our results here could be applied also for study of meson-meson resonances or for baryon-baryon scattering resonances, with small changes. As has been noted in the previous paper/l,2J the baryon octet (N, E, l.', A) and the meson octet (K, K, rr, rr0') belong to irreducible representations U3 (1, 0, -1) of the 3-dimensional unitary group U 3, and they are represented by two traceless tensors N/ and f/', respectively, as follows: