Spin contribution to light baryons in different large-N limits

We investigate the spin contribution to light baryon ground states in three inequivalent large-N limits: 't Hooft, QCD antisymmetric and QCD symmetric. Our work is based on a previous study where we have analyzed a constituent quark model with a relativistic Hamiltonian containing a stringlike confinement and a one-gluon exchange term. In this work, two spin-dependent potentials are considered and treated as perturbations: the color magnetic interaction stemming from the one-gluon exchange process and the chiral (or Goldstone) boson exchange interaction. We analytically prove that the spin contributions scale like S(S+1)/n_q, where S is the total spin and n_q is the number of quark, in agreement with diagrammatic methods. Both potentials yield also S-independent contributions which scale at most as O(n_q).