New approach to the non-diagonal QCD sum rules for pion wave functions

We test a new approach for extracting the wave functions and masses of meson resonances from the new QCD sum rules for non-diagonal correlators obtained in [1], using an exactly solvable toy model as an illustrating example. We also explore the stability of the procedure under perturbations of the theoretical part of the sum rule. In application to the pion case, this results not only in the mass and wave function of the first resonance (pi'), but also in the estimation of pi ''-mass.