$$\rho $$–Meson Form-factors in Point form of Poincaré-Invariant Quantum Mechanics

Form-factors investigation of $$\rho ^{\pm }$$ ρ ± –mesons was carried out within the framework of the relativistic quark model, based on point form of Poincaré-invariant quantum mechanics taking into account the internal structure of constituent quarks. It is shown that the parameters of the model obtained from the condition of the agreement of theoretical calculations with experimental data on leptonic decays for light $$\pi ^{\pm }$$ π ± — and $$\rho ^{\pm }$$ ρ ± –mesons lead to the results correlating with calculations in models based on light-front and instant forms of dynamics. The proposed scheme for the combined description of lepton transitions of pseudoscalar and vector mesons that is based on point form of dynamics, leads to the results on the magnetic moment of $$\rho ^{\pm }$$ ρ ± –meson correlating with the experimental data and other models.

Heavy Tetraquarks in the Relativistic Quark Model

We give a review of the calculations of the masses of tetraquarks with two and four heavy quarks in the framework of the relativistic quark model based on the quasipotential approach and QCD. The diquark-antidiquark picture of heavy tetraquarks is used. The quasipotentials of the quark-quark and diquark-antidiquark interactions are constructed similarly to the previous consideration of mesons and baryons. Diquarks are considered in the colour triplet state. It is assumed that the diquark and antidiquark interact in the tetraquark as a whole and the internal structure of the diquarks is taken into account by the calculated form factor of the diquark-gluon interaction. All parameters of the model are kept fixed from our previous calculations of meson and baryon properties. A detailed comparison of the obtained predictions for heavy tetraquark masses with available experimental data is given. Many candidates for tetraquarks are found. It is argued that the structures in the di-J/ψ mass spectrum observed recently by the LHCb collaboration can be interpreted as ccc¯c¯ tetraquarks.

Мeson resonances in the relativistic quark model

In this paper, the relativistic quark model is developed for the study of mesons and resonances as quasi-bound quark states. A classic analogue of the spinless Salpeter equation is analyzed. It is shown that the potential for a conservative isolated two-particle system is the Lorentz-scalar function of the distance between quarks and can be included into the particle mass, which leads to the position-dependent quark mass. The funnel-type potential is modified with taking into account the dependence of the strong coupling αS on the distance. The concept of free motion of particles in a bound state is developed. The eigenvalue problem for the bound state is defined by the relativistic quasiclassical wave equation for the scalar potential. Two exact asymptotic solutions of the equation for the Coulomb and linear parts of the potential are obtained analytically; on this basis, the complex-mass formula for mesons and resonances is written. The efficiency of the model is demonstrated by comparison of the calculation results with the data for the masses of ρ and D mesons.

Heavy Baryon Spectroscopy in the Relativistic Quark Model

Masses of heavy baryons are calculated in the framework of the relativistic quark-diquark picture and QCD. The obtained results are in good agreement with available experimental data including recent measurements by the LHCb Collaboration. Possible quantum numbers of excited heavy baryon states are discussed.