Calculation of hyperfine splitting in mesons using configuration interaction approach

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-range part of the potential cannot be pure scalar an d that a vector-scalar mixture is favored. Excellent spin-spin splittings o f heavy quarkonia are obtained with the same parameters as the ones which g ive the correct average mass spectrum. The results are obtained by going be yond the usually used perturbation method, namely using a configuration int eraction approach.