We present the first phenomenological study of the masses of orbitally
excited baryons in large N-c QCD. Restricting here to the nonstrange
sector of the l = 1 baryons, the 1/N-c expansion is used to order and
select a basis of effective operators that spans the nine observables
(seven masses and two mixing angles). Fits are performed using subsets
of the complete set of nine operators, including corrections up to O(
1/N-c) where leading order is N-c(1). This study shows that the 1/N-c
expansion provides an excellent framework for analyzing the mass spect
rum, and uncovers a new hierarchy of operator contributions. (C) 1998
Elsevier Science B.V. All rights reserved.