The extended chiral quark model confronts QCD

We discuss the truncation of low energy effective action of QCD below the c hiral symmetry breaking (CSB) scale, including all operators of dimensional ity less or equal to 6 which can be built with quark and chiral fields. We perform its bosonization in the scalar, pseudoscalar, vector and axial-vect or channels in the large-N-c and leading-log approximation. Constraints on the coefficients of the effective lagrangian are derived from the requireme nt of Chiral Symmetry Restoration (CSR) at energies above the CSB scale in the scalar-pseudoscalar and vector-axial-vector channels, from matching to QCD at intermediate scales, and by fitting some hadronic observables. In th is truncation two types of pseudoscalar states (massless pions and massive H-mesons), as well as a scalar, vector and axial-vector one arise as a cons equence of dynamical chiral symmetry breaking. Their masses and coupling co nstants as well as a number of chiral structural constants are derived. A r easonable fit of all parameters supports a relatively heavy scalar meson (q uarkonium) with the mass similar to 1 GeV and a small value of axial pion-q uark coupling constant g(A) similar or equal to 0.55.