Linear or linear plus Coulomb potential for description of quarkonium spectra?

In previous works we explained the S and P-wave data on heavy quark spectroscopy for the spin-independent potential given by the combination of linear, harmonic or power-law and colour-Coulomb potentials. In the present work, we try to understand the same quarkonium spectra when the spin-independent part of the potential contains the linear potential only and the colour-Coulombic piece is treated perturbatively. We find that the present model cannot explain almost all the features of S and P-wave data even at the cost of a large value of QCD scale parameter. (orig.)