Hadron Spectrum and Infrared-Finite Behavior of QCD Running Coupling

We study the behavior of the QCD effective coupling alpha(s) in the low-energy region by exploiting the conventional meson spectrum within a relativistic quantum-field model based on analytical confinement of quarks and gluons. The spectra of quark-antiquark and two-gluon bound states are defined by using a master equation similar to the ladder Bethe-Salpeter equation. A new, independent and specific infrared-finite behavior of QCD coupling is found below energy scale similar to 1 GeV. Particularly, an infrared-fixed point is extracted at alpha(s)(0) similar or equal to 0.757 for confinement scale Lambda = 345 MeV. We provide a new analytic estimate of the lowest-state glueball mass. As applications, we also estimate masses of some intermediate and heavy mesons as well as the weak-decay constants of light mesons. By introducing only a minimal set of parameters (the quark masses m(f) and Lambda) we obtain results in reasonable agreement with recent experimental data in a wide range of energy scale similar to 0.1-10 GeV. We demonstrate that global properties of some low-energy phenomena may be explained reasonably in the framework of a simple relativistic quantum-field model if one guesses correct symmetry structure of the quark-gluon interaction in the confinement region and uses simple forms of propagators in the hadronisation regime. The model may serve a reasonable framework to describe simultaneously different sectors in low-energy particle physics. DOI: 10.1134/S1063779612010030