Splitting of the pi - rho spectrum in a renormalized light-cone   QCD-inspired model
  We show that the splitting between the light pseudo-scalar and vector meson states is due to the strong short-range attraction in the ^1S_0 sector which makes the pion and the kaon light particles. We use a light-cone QCD-inspired model of the mass squared operator with harmonic confinement and a Dirac-delta interaction. We apply a renormalization method to define the model, in which the pseudo-scalar ground state mass fixes the renormalized strength of the Dirac-delta interaction. 
T. Frederico, Hans-Christian Pauli, and Shan-Gui Zhou