QCD and resonance physics. applications

Resonance properties are investigated within the QCD-based approach to resonance physics developed earlier. We extend first the dispersion charmonium theory to include power terms due to the non-perturbative effects of QCD. As a byproduct, an estimate for the gluonic vacuum expectation value, 〈0|G_μν^aG_μν^a|0〉, emerges. The main emphasis is made on the analysis of the ρ{variant}, ω, φ{symbol}, K^* mesons. Predictions are formulated for integrals of the type ∫ Im Π e^-s/M² ds where Im Π is aan appropriate spectral density. It is shown that there exist such M² that the integrals are dominated by a single resonance, on one hand, and are calculable in a reliable way, on the other. As a result we are able to calculate the resonance coupling constants and masses. The typical accuracy achieved is about 10%. The power terms considered explain both the π-ρ{variant}-A₁ mass splittings and the observed pattern of the SU(3) symmetry breaking in the vector nonet. We discuss, also, the relation between our approach and more traditional ones. A few original remarks concerning the MIT bag model, instanton calculus, etc. are included.