Nonlocal chiral quark models with wavefunction renormalization: sigma   properties and \pi-\pi scattering parameters
  We analyze the sigma meson mass and width together with the pion-pion scattering parameters in the context of non-local chiral quark models with wave-function renormalization (WFR). We consider both non-local interactions based on the frequently used exponential form factor, and on fits to the mass and renormalization functions obtained in lattice calculations. In the case of the sigma properties we obtain results which are less dependent on the parameterization than in the standard local NJL model, and which are in reasonable agreement with the recently reported empirical values. We also show that the inclusion of the WFR tend to improve the description of the $\pi-\pi$ scattering parameters, with the lattice inspired parameterization providing the best overall results. Finally, we analyze the connection of the non-local quark models discussed here with Chiral Perturbation Theory, and present the model predictions for the low energy constants relevant for $\pi-\pi$ scattering to O(4) in the chiral expansion. 
S. Noguera and N.N. Scoccola