Classification of the scalar mesons: A strange pole expedition into charm and beauty territory

The classification of scalar and vector mesons is reviewed within the framework of the Resonance-Spectrum Expansion (RSE). This method allows a simple and straightforward description of non-exotic meson-meson scattering, incorporating the effects of quark confinement and OZI-allowed decay in a fully nonperturbative way. Results for resonances and bound states are compared to experiment, on the basis of computed pole positions and cross-sections. New predictions for open-charm and -bottom scalar mesons are presented. Concretely, observed vector states for u (u) over bar -d (d) over bar, s (s) over bar, c (c) over bar and b (b) over bar are reproduced, and others are predicted. In the light scalar sector, the now established two nonets, one below 1 GeV and one in the region 1.3-1.5 GeV, are easily described, through the appearance of extra poles in the S-matrix. The recently found D-s0*(2317) meson is accurately reproduced by the same mechanism, as a quasi-bound state in the coupled c (s) over bar -DK system. In S-wave Dpi and Bpi scattering, new resonances are foreseen close to threshold, i.e. a D-0* at 2.16 +/- 10.05 GeV some 250 MeV wide, and a B-0* at 5.47 +/- 0.05 GeV with a width of about 50 MeV. Additional predictions concern the existence of b (s) over bar and b (c) over bar scalar mesons, stable with respect to OZI-allowed decay to BK and BD, respectively, namely at 5.61 +/- 0.05 GeV resp. 6.64 +/- 0.05 GeV.