The spin -spin mass splitting of light, heavy and mixed mesons are described within a good accuracy in the potential model with screened potential. We conclude that the long -distance part of the potential cannot be pure scalar and that a vector -scalar mixture is favoured. With the same parameters which gives correct average mass spectrum excellent spin -spin splittings of heavy quarkonia is obtained. The results are obtained by going beyond usually used perturbation method, namely using configuration interaction approach.
Based on the numeric solution of a system of coupled channels for vector
mesons ($S$- and $D$-waves mixing) and for tensor mesons ($P$- and $F$-waves
mixing) mass spectrum and wave functions of a family of vector mesons
$q\bar{q}$ in triplet states are obtained. The calculations are performed using
a well known Cornell potential with a mixed Lorentz-structure of the
confinement term. The spin-dependent part of the potential is taken from the
Breit-Fermi approach. The effect of singular terms of potential is considered
in the framework of the perturbation theory and by a configuration interaction
approach (CIA), modified for a system of coupled equations. It is shown that
even a small contribution of the $D$-wave to be very important at the
calculation of certain characteristics of the meson states.Comment: 12 pages, LaTe
The problem of glueball mass spectra using the relativistic Dirac equation is studied. Also the Breit-Fermi approach used to obtaining hyperfine splitting in glueballs. Our approach is based on the assumption, that the nature and the forces between two gluons are the short-range. We were to calculate the glueball masses with used screened potential.
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