Meson Properties in the 1/N_c-corrected NJL model
  Properties of mesons are investigated within the Nambu--Jona-Lasinio model. We include meson-loop corrections, which are generated via a systematic 1/N_c-expansion in next-to-leading order. We show that our scheme is consistent with chiral symmetry, in particular with the Goldstone theorem and the Gell-Mann Oakes Renner relation. The numerical part focuses on the pion and the rho-meson sector. For the latter the 1/N_c-corrections are crucial in order to include the dominant rho -> pi pi-decay channel, while the leading-order approximation only contains unphysical q\bar q-decay channels. We show that a satisfactory description of the pion electromagnetic form factor can be obtained. Similarities and differences to hadronic models are discussed. 
M. Oertel, M. Buballa and J. Wambach