New look at the $[{\bf 70},1^-]$ baryon multiplet in the $1/N_c$ expansion

So far, the masses of excited states and in particular those of nonstrange baryons belonging to the $[{\bf 70},1^-]$ derived in the $1/N_c$ expansion were based on the separation of a system of $N_c$ quarks into an symmetric core and an excited quark. Here we avoid this separation and show the advantages of this new approach. The basic conclusion is that the first order correction to the baryon masses is of order $1/N_c$ instead of order $N^0_c$, as previously found. The conceptual difference between the ground state and the excited states is therefore removed