P11π−NScattering and BrokenSU(3)

Abstract

A dynamical model based on considerations of S U (3) symmetry is presented to explicate the observed behavior of Pn, vN scattering. In SU (3) -symmetric P 8 -£ 8 scattering in the | + state, one should expect a 10 resonance as well as an 8 bound state. The possibility that this antidecuplet should be identified with the Roper resonance (1470 MeV) is explored in a broken-symmetry calculation. The model yields values for the nucleon mass, the TriV coupling constant, the phase-shift zero, the position and width of the Roper resonance, and the Pn scattering length in good agreement with the data. It is_ argued that this presents a strong case for the view that the Roper resonance is an element of a broken 10 multiplet.