1/N_c Corrections in Meson-Baryon Scattering
  Corrections to meson/ground-state baryon scattering amplitudes in the 1/N_c expansion of QCD have previously been shown to be controlled by the t-channel difference |I_t - J_t| of isospin and angular momentum and by the change of hypercharge Y_t. Here we derive the corresponding expressions in the original scattering s channel, allowing for nonzero meson spin and nontrivial SU(3) flavor quantum numbers, and provide explicit examples of the crossing relevant for pi N --> rho N and K N scattering. 
Herry J. Kwee, Richard F. Lebed