Next to leading order calculation with dimensional regularization in   Nambu--Jona-Lasinio Model
  The Nambu--Jona-Lasinio model is investigated in the $1/N_c$ expansion with the dimensional regularization. At the four-dimensional limit the meson propagators have simple forms in the leading order of the $1/N_c$ expansion. Thus the next to leading order calculation reduces to an ordinary one loop calculation. Here we obtain an explicit form of the $1/N_c$ correction and numerically evaluate the $N_c$ dependence for the gap equation. 
T. Inagaki, D. Kimura, H. Kohyama
hep-ph