Gluon exchange in meson spectroscopy

We discuss the spin structure of N = L = 0 and N = L = 1 mesons in terms of the one-gluon exchange model with scalar confinement of quarks. SU(3)sub(flavour) is broken by taking different masses for the quarks and the SU(3) breaking of the nonperturbed hamiltonian is shown to be very important in understanding the hyperfine splittings in the ground state mesons, including the charmed states. A fit to the experimental mass spectrum is performed for the N = L = 0 and N = L = 1 levels simultaneously. The spin-orbit splittings of the spectrum cannot be explained by the convential terms from gluon exchange and scalar confinement. We argue that additional terms, which break the ideal mixing pattern, have to be present. The inclusion of such a term gives a dramatic improvement in chi2 and leads to an almost perfect fit to the data for masses and mixing angles. (orig.) 891 HSI/orig. 892 HIS