The study is devoted to the systematic construction and development of effective and interrelated relativistic models based on analytic confinement (AC) for the qualitative and quantitative description of a wide range of phenomena in hadron physics, such as confinement, the running strong coupling constant, mass generation of mesons and glueballs, and decays of charmonia and exotic XYZ hadrons.
A self-consistent relativistic quantum field model of infrared confinement has been constructed, based on three principles: the concept of AC, implemented through quark and gluon propagators taken as entire analytic functions; the Weinberg-Salam compositeness condition (the vanishing of the hadron wave function renormalization constant); and the solution of the relativistic Bethe Salpeter equation in the ladder approximation. The model contains a minimal number of parameters, fixed by fitting to experimental data.
Within a unified approach, the mass spectra and weak decay constants of mesons have been reproduced across the range from light to heavy mesons with an accuracy of no more than a few percent. An independent estimate of the mass of the lowest-lying scalar glueball has been obtained, consistent with predictions from lattice QCD. A method for determining the effective QCD coupling constant in the infrared region from the meson spectrum has been proposed; an estimate of the infrared fixed point has been found, consistent with other phenomenological approaches.
A related "covariant confined quark model" (with a cutoff of the Fock-Schwinger integral over quark loops) has been developed, and a variational principle has been formulated, based on the compositeness condition and the smoothness criterion for the Fermi coupling constant.
A detailed analysis of radiative transitions in charmonium has been carried out. A unified description of the radiative transitions of six S- and P-wave charmonium states has been achieved with a single parameter. The calculated partial decay widths of the ground and orbitally excited states are in good agreement with the PDG data. The results are stable upon removing the infrared cutoff.
Strong decays of exotic states, interpreted as four-quark structures of molecular type, have been studied. For the three-body decay of Y(4230), a cascade mechanism via scalar resonances has been proposed, with the amplitudes described by a modified Breit-Wigner form. The predicted ratio of the decay channel widths involving kaon and pion production is consistent with the BESIII measurements.
It has been shown that the ratio of the partial widths of the two-body decays of X2(4014) into vector mesons is a stable quantity, weakly dependent on the model parameters. This differs from the predictions of other approaches and is explained by the absence of threshold effects in the quark loops in the CCQM.
(based on D.Sci. thesis)