Compositeness of the Delta(1232) resonance in pi N scattering

Abstract

We evaluate the $\pi N$ compositeness of the $\Delta (1232)$ resonance so as to clarify the internal structure of $\Delta (1232)$ in terms of the $\pi N$ component. Here the compositeness is defined as contributions from two-body wave functions to the normalization of the total wave function and is extracted from the $\pi N$ scattering amplitude. In this study we employ the chiral unitary approach with the interaction up to the next-to-leading order plus a bare $\Delta$ term in chiral perturbation theory and describe $\Delta (1232)$ in an elastic $\pi N$ scattering. Fitting the $\pi N$ scattering amplitude to the solution of the partial wave analysis, we obtain a large real part of the $\pi N$ compositeness for $\Delta (1232)$ comparable to unity and non-negligible imaginary part as well, with which we reconfirm the result in the previous study on the $\pi N$ compositeness for $\Delta (1232)$.

4 pages, 1 eps figure, talk given at the 10th International Workshop on the Physics of Excited Nucleons (NSTAR2015), Osaka, Japan, 25-28 May 2015

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