Towards light scalar meson structure in terms of quark and gluon degrees   of freedom
  The origin of the lightest scalar mesons is studied in the framework of instanton liquid model (ILM) of the QCD vacuum. The impact of vacuum excitations on the sigma-meson features is analyzed in detail. In particular, it is noticed that the changes produced in the scalar sector may unexpectedly become quite considerable in spite of insignificant values of corrections to the dynamical quark masses and then the medley of sigma-meson and those excitations may reveal itself as broad resonance states of vitally different masses. 
S.V. Molodtsov, T. Siemiarczuk, A.N. Sissakian, A.S. Sorin, G.M.   Zinovjev