Heavy Quarkonia In The Relativistic Quark Model

Heavy quarkonium properties are studied in the relativistic quark model based on the quasipotential approach in the quantum field theory. Since quantum chromodynamics(QCD) is nonperturbative in the infrared region as the basic theory of strong interaction, the potential model as one of various models inspired by QCD has been developed to explain the properties of hadron. At present,a large amount of experimental data on the masses of ground and excited states of heavy mesons has been accumulated. By comparing theoretical predictions with experimental data, one can obtain a valuable information on the form of the qq interaction potential. Such information is of great practical interest, since at present it is not possible to obtain the quark-antiquark(qq) potential in the whole range of distances from the first principles of QCD. In this region it is necessary to account for nonperturbative effects connected with the complicated structure of QCD vacuum. All this leads to a theoretical uncertainty in the qq potential at intermediate and large distances. It is just in this region of intermediate and large distances that most of the basic meson chracteristics are formed. This makes it possible to investigate the low-energy re-gion of strong interaction by studing the spectra and decays of heavy quarkonia.First, the Cornell potential is used widely as phenomenological potentail and takes rather success in explaining the heavy quarkonium properties. The problem is how to consider the relativistic corrections to this potential. Adopting the assummation that the quark interaction is the sum of the usual one-gluon direct exchange and the mixture of linear scalar and vector potentials, we structure the relativistic corrections of order v2/c2to the Cornell potential, including the annihilation potential for the quark and antiquark of the same favors which plays the same role with the one-gluon direct exchange at short distances. The effects of the relativistic corrections on the hyperfine splittings of quarkonium states are discussed, and a good fit to the available experimental data is obtained on heavy quarkonium mass spectra.Second, the quark potential has to be at present determined phe-nomenologically due to QCD nonperturbation and the mechanism of quark confinement is still in search. We obtain a new quark potential from the effective dilaton-gluon-coupling inspired by superstring theory, and by using this static potential, we explore the mechanism of quark confinement through calculations of the spin-average energy levels, the widths of the leptonic decays and radiative transitions for heavy quarkonium. The obtained results are compared with that of the Cornell potenial.Further works are clearly needed to develop the model to reach a better understanding of the heavy meson properties, and to extendinvestigation of baryon properties.