Sala Seminarios IFIC (Edf. Institutos de Investigación)
Sala Seminarios IFIC
Edf. Institutos de Investigación
Descripción
The spectra of masses and decay constants for non-strange meson resonances in the energy range 0--2.5 GeV are analyzed. It is known from meson phenomenology that for given quantum numbers these spectra approximately follow linear trajectories with a universal slope. This fact can beunderstood in terms of an effective string description for QCD. For light meson states the trajectories deviate noticeably from the linear behavior. We investigate the possible corrections to the linear trajectories by matching two-point correlators of quark currents to the Operator Product Expansion (OPE). We find that the allowed modifications to the linear Regge behavior must decrease rapidly with the principal quantum number. After fitting the lightest states in each channel and certain low-energy constants the whole spectrum for meson masses and residues is obtained in a satisfactory agreement with phenomenology. We show also how such important features of QCD as the chiral symmetry breaking and the formation of mass-gap can be directly traced from the QCD sum rules. As a result the whole meson mass spectrum can be parametrized with a good accuracy by the weak pion decay constant only.