LOWEST NEGATIVE PARITY BARYONS IN THE 1/N_c EXPANSION

摘要

We review a recently proposed approach to study the lowest negative parity baryons within the 1/N_c expansion. The method is based on the derivation of the matrix elements of SU(2N_f) generators for mixed symmetric [N_c - 1,1] flavor-spin states. Presently it is applied to the N = 1 band and a comparison is made with a former method based on the decoupling of the system into a symmetric core of N_c — 1 quarks and an excited one. We prove that the decoupling is not necessary and moreover, it misses some important physical consequences.